www.elektor.com

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December 2011 AUS$ 14.50 - NZ$17.50 - SAR 102.95 - NOK99 £4.80

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New 8-bit Microcontrollers with integrated configurable
logic in 6- to 20-pin packages

Microchip's new PIC10F/LF32X and PIC1 2/1 6F/LF1 50X 8-bit microcontrollers
(MCUs) let you add functionality, reduce size, and cut the cost and power
consumption in your designs for low-cost or disposable products, with
on-board Configurable Logic Cells (CLCs), Complementary Waveform
Generator (CWG) and Numerically Controlled Oscillator (NCO).

The Configurable Logic Cells (CLCs) give you software control of combinational and
sequential logic, to let you add functionality, cut your external component count and save
code space. Then the Complementary Waveform Generator (CWG) helps you to improve
switching efficiencies across multiple peripherals; whilst the Numerically Controlled
Oscillator (NCO) provides linear frequency control and higher resolution for applications
like tone generators and ballast control.

FAST-START
DEVELOPMENT TOOLS

PICDEM™ Lab Development
Kit -DM163045

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PIC10F/LF32X and PIC12/16F/LF150X MCUs combine low current consumption, with an
on-board 16MHz internal oscillator, ADC, temperature-indicator module, and up to four
PWM peripherals. All packed into compact 6- to 20-pin packages.

Platform - DM164130-1

PICkit™ Low Pin Count Demo
Board -DM164120-1

Free CLC Configuration Tool:

www.microchip.com/get/eucktool

Go to www.microchip.com/get/eunew8bit to find out more about
low pin-count PIC® MCUs with next-generation peripherals

microchip

www.mlcrochipdlrGct.CDm

www.microchip.com

& Microchip

The Microchip name and logo, HI-TECH C, MPLAB, and PIC are registered trademarks Bar<£f3linpt(I^^Pl i ia i idhtes.A, and&tekctoFitries. mTouch, PICDEM, PICkit, and REAL ICE, are trademarks of Microchip Technology Inc. in the U.S.A.,
and other countries. All other trademarks mentioned herein are the property of their respective companies. © 2011, Microchip Technology Incorporated. All Rights Reserved. DS30629A. ME293AEng/09.1 1

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Personal Download for I © Elektor

Elektor’s air intake

One of the most frequent questions I get,
usually by email and occasionally by tel-
ephone or letter (hey!) is: “can I contribute
to your wonderful publication and if so,
what are the requirements and the specific
subjects you are interested in?” The
answer is invariably, “Yes, please, we’re
ready to evaluate the publication value
of your article proposal. Every edition of
Elektor covers a wide variety of subjects
and fields of interest. Please review our
Author Guidelines, they’re available under
the Service tab on our website at www.
elektor.com. To this I usually add a few
encouraging words like “we’ve been
around since 1974” and some guidance on
the size of the article. Some authors have
been with us for many years and are totally
at ease with supplying copy and illustra-
tions in the preferred ways; others need
extensive assistance with the file formats,
spelling issues, style or the depth of the
technical content they can manage.

The air intake is actually a manifold —
contributions from companies, journalists
and specialists in the industry are also
welcomed. The approach works well but
also creates a queue of articles awaiting
publication and in many cases we have to
reassure authors that they aren’t forgotten
and their project is being worked on in the
Elektor Lab.

Now, for the solemn bit: about 7 out of 10
article proposals reaching us through all
international channels sadly gets rejected
for publication. The reasons for the team
of editors and designers to be so harsh and
unkind to budding authors are diverse:
uninventive use of components; ditto for
obsolete components; ragchewing manu-
facturer’s datasheets or old Elektor articles
(!); nebulous circuits nicked from nebu-
lous websites, poor electronic design and
attempts to use the magazine to get rid of
stock gathering dust. The rest is happily
considered for publication or post-engi-
neering by our lab, no matter if the piece
is poorly written or the prototype built
on breadboard — in general we are good
humoured with a keen eye for originality.
Even if it takes a while for us to get back to
you due to the workload here at Elektor
House, give us a try and eventually see
your name (and circuit!) in print — it’s by
no means difficult, we’re here to help.

Enjoy reading this edition,

Jan Buiting, Editor

6 Colophon

Who’s who at Elektor.

8 News & New Products

A monthly roundup of all the latest in
electronics land.

16 Android as a Development Platform

Tablet PCs are cheap and make excellent
embedded devices. Here’s how.

20 Time-lapse Photography with an
Android Tablet

With an Android tablet and a handful of
hardware, you can put together a remote
control for a still camera doing time-lapse
photography.

24 The PCB Prototyper in Practice

Here’s a user report on the advanced PCB
milling machine sold by Elektor.

26 Robusta: a Satellite built by Students

Montpellier University’s cubesat
picosatellite carries a scientific
experiment of interest to the space
community.

32 Xport your Ideas to the Web

Lantronix’ Xport Pro device proves
remarkably simple to configure and use as
an advanced network interface module.

38 Here comes the Bus! (10)

This month we come to grips with
interfacing a high precision ADC to the
bus, using a slick HTML interface.

43 E-Labs Inside: Work in progress

Some pictures taken in the Elektor Labs of
projects under active development.

44 E-Labs Inside: LED Exorcism

The riddle solved of the ‘LED that flashed
before-it died’.

45 E-Labs Inside: Pins to length

Howto prevent DOCM displays from being
damaged when fitting them on a board.

46 E-Labs Inside: Itsy Bitsy Spider...

Here’s how we solved another fine mess
caused by a mixup between TSSOP and
SOIC packages.

4

Personal Download for I © Elektor

12-2011 elektor

CONTENTS

Volume 37
December 2011

no. 420

16 Android

as a Development Platform

Tablet computers (PCs) running the Android operating system are now available
for under 100 pounds/euros. They are packed full of electronics and are visually
attractive. Many functions that cost considerable effort to implement in an em-
bedded environment are standard features in tablet computers. In this article we
examine the factors involved in using tablet PCs in electronics projects.

20 Time-lapse Photography
with an Android Tablet

The design described here can be used with a still camera to cause it to take
pictures at regular intervals. If you make a film from these pictures, the result is
what is called a time-lapse film in which hours or even days are reduced to a few
seconds. The project described here operates the camera button mechanically
using a servo of the sort used in RC (remote controlled) models.

60 Electronic LED Candle

Imitation candles using an LED as the illuminating element are available com-
mercially. But here we’re describing a rather different project with a few unus-
ual characteristics — after all, candles are meant to be blown out!

66 USB Data Logger

The USB data logger described here is a low-energy, universal solution to the
problems with adding EEPROM and RAM to microcontrollers performing data
logging functions. It takes all the serial data sent from any external micro and
stores it in a file on a USB memory stick which can be analysed later with a PC.

46 Smelly Bus

Nasty fumes and odours from a blown
electrolytic capacitor, but no major
worries!

48 Pick-proof Lock

Here we show how the very secure 128-bit
AES encryption scheme can be applied to
an infrared remote control.

52 Audio DSP Course (6)

This month we use our DSP board to build
a lab-grade DDS signal generator.

60 Electronic LED Candle

The unique feature of this ersatz candle is
that you can actually blow it out!

64 Turn your Oscilloscope into a Reflec-
tometer

Combine an oscilloscope and a signal
generator to do measurements on (long)
cables.

66 USB Data Logger

Got a USB stick? And a microcontroller
outputting serial data you want to store?
Then this design is foryou.

70 LED Cycle Lamp

It’s Lithium-Ion powered and has 600
lumen on tap. Check it out.

74 Gerard’s Columns:

Speaking out Loud

From our monthly columnist Gerard
Fonte.

75 Hexadoku

Elektor’s monthly puzzle with an
electronics touch.

76 Retronics:

RCA Cosmac
Development System IV
(CDP18S008) (ca. 1978)

hELLO wORLD from Embedrock City.
Series Editor: Jan Buiting

84 Coming Attractions

Next month in Elektor magazine.

elektor 12-2011

Personal Download for I © Elektor

5

elektor

international media bv

Elektor International Media provides a multimedia and interactive platform for everyone interested
in electronics. From professionals passionate about their work to enthusiasts with professional
ambitions. From beginner to diehard, from student to lecturer. Information, education, inspiration
and entertainment. Analogue and digital; practical and theoretical; software and hardware.

Ejg;es time-lapse'photography.

M‘ i iq 1 2 8-bil At t?i ll r y pticui

USB Data Logger

Store serial datrt conveniently, safely

Electronic
LED Candle

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ektor

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ANALOGUE • DIGITAL'
MICROCONTROLLERS & EMBEDDED

AUDIO

TEST & MEASUREMENT

■ Ipf

Volume 37, Number 420, December 2011 ISSN 1757-0875

Elektor aims at inspiring people to master electronics at any
personal level by presenting construction projects and spotting
developments in electronics and information technology.

Publishers: Elektor International Media, Regus Brentford,

1000 Great West Road, Brentford TW8 9HH, England.

Tel. (+ 44 ) 208 261 4509, fax: (+ 44 ) 208 261 4447
www.elektor.com

The magazine is available from newsagents, bookshops and
electronics retail outlets, or on subscription.

Elektor is published 11 times a year with a double issue for July & August.

Elektor is also published in French, Spanish, American English,
German and Dutch. Together with franchised editions the
magazine is on circulation in more than 50 countries.

International Editor:

Wisse Hettinga (w.hettinga@elektor.nl)

Editor: Jan Buiting (editor@elektor.com)

International editorial stafl Harry Baggen, Thijs Beckers,
Eduardo Corral, Ernst Krempelsauer, Jens Nickel, Clemens Valens.

Design stafl Christian Vossen (Head),

Thijs Beckers, Ton Ciesberts, Luc Lemmens,

Raymond Vermeulen, Jan Visser.

Editorial secretariat:

Hedwig Hennekens (secretariat@elektor.com)

Graphic design / DTP: Giel Dols, Mart Schroijen

Managing Director / Publisher: Don Akkermans
Marketing: Carlo van Nistelrooy

Subscriptions: Elektor International Media,

Regus Brentford, 1000 Great West Road, Brentford TW8
9HH, England.

Tel. (+44) 208 261 4509, fax: (+44) 208 261 4447
Internet: www.elektor.com/subs

6

Personal Download for I © Elektor

12-2011 elektor

Elektor eC-reflow-mate

Professional SMT reflow oven with unique features

r

The eC-reflow-mate is ideal for assembling prototypes and small production batches of PCBs with SMD
components. This SMT oven has a very large heating compartment, which provides plenty of space for several
PCBs. The accompanying PC software allows you to monitor the temperature curves of all sensors precisely
during the soldering process, and it enables you to modify
existing temperature/time profiles or create new ones. Special features:

• Optimal temperature distribution thanks to
special IR lamps

• Drawer opens automatically at end of soldering
process

• Glass front for easy viewing

Technical specifications:

• Supply voltage: 230 V/ 50 Hz only

• Power: 3500 W

• Weight: approx, 29 kg

• Dimensions: 620 x 245 x 520 mm (W x H x D)

• Heating method: Combined IR radiation and
hotair

• Operation: Directly using menu buttons and LCD
on oven

• Remotely using PC software and USB connection

• Temperature range: 25 to 300 °C

• Maximum PCB size: 400x285 mm

• Temperature sensors: 2 internal and 1 external
(included)

V.

Price:

£21 70.00 / € 2495.00 / US$3495.00
(plus VAT and Shipping)

Further information and ordering at

www.elektor.com/reflow-mate

Email: subscriptions@elektor.com

Rates and terms are given on the Subscription Order Form.

Head Office: Elektor International Media b.v.

P.O.Box ii NL-6114-ZC Susteren The Netherlands
Telephone: (+31) 46 4389444, Fax: (+31) 46 4370161

Distribution:

Seymour, 2 East Poultry Street, London ECiA, England
Telephone:+44 207 429 4073

UK Advertising:

Elektor International Media b.v.

P.O.Box 11 NL-6114-ZG Susteren The Netherlands
Telephone: (+31) 46 4389444, Fax: (+31) 46 4370161

Email: t.vanhoesel@elektor.com

Internet: www.elektor.com

Advertising rates and terms available on request.

Copyright Notice

The circuits described in this magazine are for domestic use
only. All drawings, photographs, printed circuit board layouts,
programmed integrated circuits, disks, CD-ROMs, software
carriers and article texts published in our books and magazines
(other than third-party advertisements) are copyright Elektor
International Media b.v. and may not be reproduced or transmit-
ted in any form or by any means, including photocopying, scan-
ning an recording, in whole or in part without prior written per-
mission from the Publisher. Such written permission must also be
obtained before any part of this publication is stored in a retrieval

system of any nature. Patent protection may exist in respect of
circuits, devices, components etc. described in this magazine.
The Publisher does not accept responsibility for failing to identify
such patent(s) or other protection. The submission of designs or
articles implies permission to the Publisher to alter the text and
design, and to use the contents in other Elektor International
Media publications and activities. The Publisher cannot guaran-
tee to return any material submitted to them.

Disclaimer

Prices and descriptions of publication-related items subject to
change. Errors and omissions excluded.

© Elektor International Media b.v. 2011 Printed in the Netherlands

elektor 12-2011

Personal Download for I © Elektor

7

NEWS & NEW PRODUCTS

DB9 USB-to-digital modules introduced by FTDI

USB solutions specialist Future
Technology Devices Inter-
national Limited (FTDI) has
added a series of USB to dig-
ital level interface modules,
in DB9 form factors, to its
product portfolio. The new
DB9-USB-D3-F (3.3 V output
female connector), DB9-USB-
D3-M (3.3 V output male con-
nector), DB9-USB-D5-F (5 V
output female connector)
and DB9-USB-D5-M (5 V out-
put male connector) enable
implementation of USB interconnection into legacy equipment without the need for
alteration of the enclosure or for any noticeable increase in the overall bill of materials.
These modules all utilize FTDI’s FT232R USB to serial UART bridge chip, which is capa-
ble of supporting data rates of 1 2 Mbits/s (USB Full Speed). They allow for the quick
and easy upgrading of pieces of hardware to today’s most widely used serial interface
standard in a highly convenient and cost effective manner. Drivers for the modules are
available to download direct from the FTDI website.

Supplied in a compact 30.8 mm x 19.8 mm x 1 1 .5 mm package, each of the modules
uses a standard USB mini-B connector. They have an operational temperature range of
-40 °C to +85 °C, permitting them to be specified for heavy duty industrial applications.
The FTDI DB9 to digital modules are each priced at US$1 5.50 (for 1 -9 pcs). The FTDI
DB9 to digital modules datasheet is available for downloading.

www.ftdichip.com/Support/Documents/DataSheets/Modules/DS_DB9-USB.pdf (110675-XVII)

Secure RFID keys for
access control, e-Cash,
and ID cards worldwide

Maxim Integrated Products (NASDAQ:
MXIM) introduces a new line of RFID
keys and cards designed for the two-
billion-units-per-year automatic iden-
tification, access control, and elec-
tronic cash (e-cash) markets. This new
contactless RFID product family (the
MAX66000/020/040/1 00/120/140) lever-
ages the expertise utilized in the compa-
ny’s popular 1-Wire( R ) secure authentica-
tion ICs, which protect intellectual property
in embedded systems. With a 13.56 MHz
interface, these secure keys are ideally
positioned to gain market share because
13.56 MHz is becoming the worldwide
standard for access control and e-payment
applications. Some regions of the world
have already begun deploying this RFID
technology for passport and national ID
cards.

As the critical data found inside many of
these RF credentials becomes more and
more valuable, efforts to crack, counter-

feit, and duplicate cards and credentials
will increase. System integrators are already
looking for increased security and authenti-
cation techniques to protect those assets.
Maxim’s new RF devices are packaged in a
laminated plastic key fob or ISO thin card
format and are available in either the ISO
1 4443 B or ISO 15693 HF protocol. Each
protocol family offers three products: 64-bit
ROM ID only (MAX66000/MAX661 00),
ROM ID plus 1 Kbit EEPROM (MAX66020/
MAX661 20), or ROM ID plus 1 Kbit EEPROM
and SHA-1 authentication (MAX66040/
MAX66140). Custom form factors are also
available.

The MAX66040 and MAX66140 employ the
secure hash algorithm (SHA-1), a proven
technology designed by the NSA for pro-
tecting a system’s critical data without
using expensive encryption techniques or
an untested, proprietary protocol. SHA-1
is an ISO standard that is publicly avail-
able and has been thoroughly tested in the
marketplace. It is designed to maintain the
integrity of the stored data so that one can
verify the authenticity of any credential.
Maxim’s RF keys and cards are custom pro-
grammable to match the requirements of
new and existing tag populations. They
work with most 13.56 MHz readers on the
market, thus providing an alternative tag
source for existing systems.

www.maxim-ic.com/rfid (110675-VIII)

Granny knows how to
keep iPads and Tablets
clean

iPads and tablets are sure to appear on holi-
day gift lists this year again. Music, movies
and the internet all available with a simple
touch of the screen. And there’s one more
thing that comes with that simple touch:
greasy fingerprints. Thousands of them -
all over the screen! Wiping it with a shirt-
sleeve isn’t effective, and sprays, tissues and
cloths are inconvenient and only make the
fingerprint mess even worse. Now there’s a
solution.

SideKick™ by LensPen® is a new screen
cleaning tool specially designed to remove
fingerprints from iPads and tablet touch-
screens. There are no tissues, no cloths, no
sprays and no liquids. SideKick features a
patented carbon technology that quickly
and easily removes the oily fingerprints.
“It’s not high tech, it’s old tech,” said Peter
Meurrens, Vice President of Operations at
Parkside Optical and inventor of SideKick.
“My grandmother knew how to clean an

8

Personal Download for I © Elektor

12-2011 elektor

NEWS & NEW PRODUCTS

iPad forty years ago.” SideKick’s carbon
compound is similar to the one found in
printer’s ink. That carbon compound is why
newspapers have been an effective way to
clean windows for generations. “When you
get a fingerprint on a lens or a computer
screen, it’s an accident. But when you get
fingerprints on an iPad or tablet, it means
you’re using it! SideKick is not just an acces-
sory, it’s a necessity.”

SideKick is available at electronics stores
nationwide in the US. Replacement cleaning
pads are available in packages of two. Each
pad gives 1 50 cleanings. MSRP for SideKick
is $1 9.95, and $14.95 for the package of
two replacement pads.

www.lenspen.com

www.youtube.com/lenspennews

(110675-X)

Cypress: new Gen4
TrueTouch® controller
line is ultra noise resilient

Cypress Semiconductor Corp. (NASDAQ:
CY) introduced its new Gen4 family of Tru-
eTouch® touchscreen controllers. Gen4
is clainmed to deliver industry-best per-
formance in all categories, including the
world’s best Signal-to-Noise Ratio (SNR)

and unparalleled performance in the pres-
ence of all noise sources— the biggest chal-
lenge faced by touchscreen designs.

The Gen4 family was designed from the
ground up to deliver the world’s high-
est SNR in real world applications. It is the

first and only touchscreen 1C that delivers
built-in 10 V Tx to drive the touch panel
at 10 V. Because SNR is directly propor-
tional to the voltage at which the panel is
driven, this feature allows Cypress to offer
nearly four times the SNR of the next clos-
est competitor.

The Gen4 family further raises the SNR
bar as the first touchscreen device family
to completely eliminate display noise in
hardware. Gen4’s patent-pending Display
Armor™ offers unprecedented immunity to
noise from every type of display, even low
cost noisy displays such as ACVCOM LCDs.
This allows touchscreen designers to make
their products thinner by removing the air
gap between the display and the sensor,
and also less expensive by removing the
shield layer in the sensor. Display Armor
allows Gen4 to operate seamlessly with
direct lamination, on-cell and in-cell stack-
ups, regardless of the display chemistry.
The Gen4 product family offers the indus-
try’s fastest refresh rate of 400Hz, and has
the unique ability to scan a capacitive touch
panel at 1 ,000 Hz — both industry-best met-
rics. This level of performance is enabled by
the 32-bit ARM® Cortex™ core at the heart
of the Gen4 products. The Gen4 family
also provides the industry’s best accuracy
and linearity of 0.2 mm while boasting the
world’s lowest active power consumption
of 2 mW, and a deep sleep mode that only
draws 1.8 pW with wake-up via address

match on the COM port.
Gen4 also offers more
capacitive sensing I/O
than the competition,
while still fitting into the
world’s smallest touch-
screen packages. With
up to 40 I/O for mobile
phone applications, Gen4
can support up to four
standalone CapSense®
buttons while still deliv-
ering ideal sensor pitch
for up to 5-inch screens.
The Gen4 family also
offers features that only
TrueTouch can deliver,
including waterproof-
ing functionality that
allows products to meet
IP-67 standards; 1-mm stylus support for
Asian character sets and accurate handwrit-
ing capture; and hover sensing to provide
mouseover-like features and true fingernail
or thick-glove support in mobile devices.

touch.cypress.com (110675-XI)

TrueTouch® Gen4 - Rise above the Noise!

Revolutionary Touchscreen Solutions from Cypress

K’.wtPM J7F* mj_

Intersil: DC/DC Controllers
for embedded and low
power CPU/GPU cores

Intersil Corporation recently expanded its
portfolio of industry leading multi-phase DC/
DC controllers by introducing the ISL95835
and ISL95837. Both controllers provide a
complete low cost solution for CPU and
GPU core power while delivering best-in-
class transient response and efficiency. Each
complies with Intel’s IMVP-7/VR1 2™ specifi-
cation for smart voltage regulation to reduce
power dissipation in the second-generation
Intel® Core-i5/i7 processors.

Both the ISL95835 and ISL95837 are the
industry’s smallest solutions available and
offer combined functionality and reduced
pin count, saving valuable board space and
reducing the total bill of materials. The
ISL95837 has been optimized for lower
power, thin and light applications.

Compl

Dual Outputs

• Configurable 3-, 2- or
1 -phase for the 1st
Output

* 1-phase for the 2nd
Output

Features and Specifications

• The ISL95835 includes two internal MOS-
FET drivers for a 3+1 solution and can be
configured as a 3-, 2- or 1 -phase VR

• The ISL95837 can be considered as an
ISL95835 dedicated for a 1+1 application
with an output of 1 -phase VR, maximizing
flexibility

• Both devices operate in diode (or sleep)
mode when a CPU enters light load modes
for added efficiency and battery life

• Accept input voltages from 4.5V to 25V and
deliver output voltages from 0.25V to 1.5V.

The controllers are based on Intersil’s
Robust Ripple Regulator (R3)™ technology,
a hybrid of fixed-frequency PWM control
and variable-frequency hysteretic control
that delivers the industry’s fastest transient
response. The R3 modulator delivers faster
transient settling time than typical modu-
lators and automatically adapts switching
frequency to optimize light load efficiency.

www.intersil.com/products/deviceinfo asp?pn=ISI_95835
www.intersil.com/products/deviceinfo.asp7pnHSL95837

(110675-XII)

elektor 12-2011

Personal Download for I © Elektor

9

NEWS & NEW PRODUCTS

ChdrgftPeiiYt

caJ

US nationwide rollout of electric vehicle charging
stations to begin

Car Charging Group Inc. (OTCBB:CCGI), a provider of electric vehicle
(EV) charging services and Central Parking System Inc. and its sub-
sidiary, USA Parking System Inc., the nation’s largest parking garage
operator, have teamed up to provide EV charging services at loca-
tions nationwide in the US via Coulomb Technologies’ Charge-
Point® Network.

“There are close to 1 7,000 parking garages in the U.S., and they
will play one of the most vital roles in the development of a
national EV charging infrastructure,” said Brian Golomb, Direc-
tor of Sales of Car Charging. “By partnering with two of the
most important companies in this sector — companies that
understand the benefits of electric vehicles — we will move
much quicker in the rollout of this nationwide infrastructure.”
Car Charging Group plans to install EV charging stations at
sites owned by the two parking garage operators. The opera-
tors have 2,200 locations nationwide with 1 .1 million parking
spaces.

As part of the agreement, Central Parking has the right to pur-
chase five percent of the Common Stock of Car Charging Group.
We are very excited about this partnership, because it will
greatly expand the reach of our nationwide EV charging network,”
said Michael Farkas, CEO of the Miami Beach, Fla. -based Car Charg-
ing Group. “Furthermore, we hope to further enhance our already
strong relationship with these companies by giving Central Parking
the opportunity to be a shareholder in our company and to take part
with us in electrifying the U.S. transportation system.”

Central Parking believes that electric vehicles can make a difference in
the transportation sector, and they look forward to being a partner in
building a nationwide network of EV charging stations.

“Electric vehicles are no longer a mirage — they are becoming an ever
increasing presence on our roads and we are proud to be working with such an innova-
tor in the EV sector,” said James Marcum, CEO of Central Parking Systems. “By install-
ing EV charging stations in our garages, we will be providing added services to our cli-
ents and strengthening our position as an industry leader in environmentally-friendly
initiatives.”

USA Parking System, a wholly owned subsidiary of the Nashville, Tenn. -based Central
Parking System Inc. also aims to benefit both the clients and the environment through
its agreement with Car Charging.

Car Charging Group provides EV charging stations at no charge to property owners/
managers while retaining ownership, thus allowing their partners to offer their custom-
ers, tenants and employees charging services without incurring any outlay of capital. In
addition, Car Charging Group’s partners realize a percentage of the charging revenue
generated by the charging services paid for by the EV owners.

www.CarCharging.com www.Parking.com www.USAPark.com (110675-XIV)

SMI Antenna with
comprehensive
protection for automotive
applications

PREMO launches a new family of its 1 1 03
standard, universally adopted by indus-
try. This format provides up to 55 mV/

App/m sensitivity which gives it the best
sensitivity by cm 3 in the market. The new
SDTR1 1 03CAP, is a SMD antenna for low
frequency 20 kHz-1 50 kHz receiver appli-
cations. This series offers upper and lateral
side protection with co-polyamide poly-
hexamethylene polymer walls, gamma radi-
ated with high thermal stability (supports
up to 290 g C) and mechanical resistance
(exceeds 1 50 Mpa if mechanical strength).
This antenna is equipped with NiZn ferrite
core with high surface resistivity (>1 0 M £2/
mm) that provides a highly stable behavior
(rather than ±2%) over a wide temperature
range (-40 9 C to 1 25 g C).

The new SDTR1 1 03CAP is an SMD antenna
with ‘Super-Drop-Test-Resistant’ technol-
ogy with an extended range of operat-
ing temperature (-40 °C to 1 25 g C), which
makes it particularly suitable for applica-
tions such as TPMS (Tyre Pressure Monitor-
ing Systems) which requires an excellent
performance under extreme conditions,
according to AEC-Q200 and additional
requirements as EU regulations.

PREMO offers four standard values,
2.38 mH, 4.91 mH, 7.2 mH and 9 mH at
125 kHz. Others inductance values and
frequencies, from 340 pH to 1 6 mH, upon
request.

Its surface mount (SMT) allows an easy use
in the automated process of mounting cir-
cuit boards, thus eliminating any manual
handling.

www.grupopremo.com/es/file /805

(110675-XIII)

World’s first 1 CS/s USB-
powered oscilloscope

The three new oscilloscopes in the
PicoScope® 2000 Series are the first USB-
powered oscilloscopes to offer a real-time
sampling rate of 1 GS/s. With two channels,
bandwidths ranging from 50 MHz to 200
MHz, a built-in function generator, arbitrary
waveform generator and external trigger
input, these compact and economical
scopes are perfect for engineers and
technicians needing a complete test bench
in a single unit.

The scopes are supplied with a full version
of the PicoScope oscilloscope software. As
well as standard oscilloscope and spectrum
analyzer functions, PicoScope includes
valuable additional features such as serial
decoding, mask limit testing, segmented

10

Personal Download for I © Elektor

12-2011 elektor

NEWS & NEW PRODUCTS

memory and advanced triggers. It provides
a large, clear display that shows waveforms
in great detail and allows easy zooming and
panning. Other advanced features include
intensity- and color-coded persistence
displays, math channels, automatic
measurements with statistics, and
decoding of l 2 C, UART/RS232,

SPI and CAN bus data. Free
updates to the software are
released frequently.

Like all PicoScope oscilloscopes, the
new PicoScope 2000 Series devices use
digital triggering, which ensures lower
jitter, greater accuracy and higher voltage
resolution than the analog triggers found
on many other scopes. The advanced
trigger types include pulse width, interval,
window, window pulse width, level
dropout, window dropout, runt pulse,
variable hysteresis, and logic.

A Software Development Kit (SDK),
supplied free, allows you to control the new
scopes from your own custom applications.
The SDK includes example programs in
C, C++, Excel and LabVIEW. The SDK and
PicoScope are compatible with Microsoft
Windows XP, Vista and Windows 7.

The new PicoScope 2000 Series
oscilloscopes are available now from Pico
distributors worldwide and from www.
picotech.com. Prices range from £349 for
the 50 MHz PicoScope 2206 to £599 for
the 200 MHz PicoScope 2208, including a
5-year warranty.

www.picotech.com (110698-I)

New EasyPIC V7
development system

For the first time in EasyPIC’s almost
10-year history, EasyPIC v7 has grouped
PORT headers, LEDs and Buttons into Input-
Output groups, making them easier to use
than ever before. The v7 boards come
equipped with tri-state DIP switches, so
connecting pull-up or pull-down jumpers
to desired pins is now just a matter of
pushing the switch.

Connectivity is the main focus of EasyPIC
v7, providing three separate PORT headers
in the Input-Output groups and another
one on the opposite side of the board,
allowing users to access those pins from
any side.

The new board has a dual power
supply supporting both 3.3 V and 5 V
microcontrollers. It’s like having two
boards instead of one!

Probably the best feature of the v7 board
is its powerful on-board mikroProg
programmer and In-Circuit debugger
capable of programming over 250 PIC
microcontrollers. Debugging is supported
with all mikroElektronika PIC compilers —
mikroC, mikroBasic and mikroPascal.
7-segment displays have returned at the
request of many users, which brings the
number of displays on the board to three:
GLCD 128x64, LCD 2x16 character and
4-digit 7-segment displays.

EasyPIC v7 is the first board supporting

the mikroBUS pinout standard.
Mikroelektronika are preparing many
mikroBUS compatible Click Boards,
which will make development easier then
ever. No configuration or jumpering, just
plug-n-play.

The new board has the following new
modules: Serial EEPROM, Piezo Buzzer
and support for both DS1 820, and LM35
Temperature sensors.

The EasyPIC v7 User Manuals and
schematics haven been redesigned; the
documentation is now more informative
with a good number of clear photos and
expanded text sections.

www.mikroe.com (110698-II)

Sensirion: first digital
temperature sensor

Following the successful market
launch of the SHT2x family of
humidity and temperature sensors,
Sensirion is now launching a sensor
designed exclusively for temperature
measurement. The newSTS21 temperature
sensor is based on the same chip as the
SHT2x family and is housed in a tiny
DFN package measuring only 3x3 mm.
This makes the sensor ideal for use in
applications where only very limited space
is available. It also delivers outstanding
performance and remarkably high accuracy

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Personal Download for I © Elektor

11

NEWS & NEW PRODUCTS

of ±0.22 °C over the temperature range of
5 to 60 °C, combined with very low power
consumption — an especially important
consideration for battery-operated devices.
The STS21 is pin and protocol compatible
with Sensirion’s standard SHT21 humidity
sensor, but it has a different l 2 C address.
This allows the STS21 to be used as
alternative to the SHT21 in applications
where temperature measurement is
required and humidity measurement is
optional, since the same hardware can be
used with both sensors.

The STS21 temperature sensor is fully
calibrated, provides a digital output, and
is very competitively priced. It therefore
fulfills the stringent requirements of many
applications in terms of both performance
and cost effectiveness.

www.sensirion.com/sts21-datasheet

(110698-III)

132 LED driver features
industry’s highest
efficiency and smallest
size

austriamicrosystems has announced the
AS1 130, the most advanced and smallest
dot-matrix LED driver (channels vs. PCB
space) available. The AS1 130 drives 132
LEDs but requires only 5 mm 2 PCB space,
reduces external component count, allows
use of cheap connectors and requires fewer
PCB (printed circuit board) layers. Benefits
for end users include up to 80% longer
battery lifetime, more colorful effects and
smoother running animations.

Using a 12x11 cross-plexed technique,
austriamicrosystems’ AS1 1 30 LED driver is
targeted for dot-matrix displays in mobile
phones, toys, small LED displays in personal
electronics, but also non-battery powered
household goods, indoor public information
displays, and industrial applications such
as power meters. The AS1130 drives
132 LEDs, each with an 8-bit dimming
control and no external resistor required.
Additionally, an 8-bit analog current control
allows fine tuning of each current source
to compensate for different brightness
of different colors, or to adjust the white
balance on RGB LEDs, austriamicrosystems’
AS1 1 30 incorporates 36 frames of memory
for small animations or for use as a buffer to
reduce host processor load, saving energy

and processing time. The AS1 1 30 LED driver
can also extend battery life by controlling
an external power supply (e.g. charge
pump) which is required when LEDs need a
higher voltage than the battery can supply,
allowing continuous operation even under
low battery voltage conditions.

“The AS1130 dot-matrix LED driver
is designed to make driving LEDs an
easier task,” commented Rene Wutte,
austriamicrosystems’ Marketing Manager
for Lighting. “It enables driving a large
number of RGB LEDs from one 1C for creative
light designs while providing the highest
efficiency available, an important feature
for both battery-powered and AC-powered
applications. The AS1 1 30’s features simplify
design and programming, optimize total
cost, and allow developers to provide the
lighting features required to stay ahead in

this market.”

In addition to the ultra-small sized CS-WLP-20,
the AS1 1 30 LED driver is also available in a gull
winged SSOP-28 package, allowing easier
handling in applications that are not so space
sensitive. This makes the AS1 130 a perfect
replacement for indoor high pixel density
video walls, easily replacing up to eight
16-channel PWM LED drivers, or reducing
the complexity of externally (user designed)
multiplexed systems.

Only 12 lines are required to drive all
132 LEDs. This is accomplished with
austriamicrosystems’ multiplexing technique
called cross-plexing. It reduces line count on
the PCB as well as pins on the connectors,
saving space & costs. Other features include
control via a 1 MHz l 2 C compatible interface,
open and shorted LED error detection, and
low-power shutdown current.

The AS1 130 LED driver operates over a
temperature range of -40 to +85°C and a
wide 2.7 to 5.5 V power supply range.

www.austriamicrosystems.com/LED-driver/

AS 1130

(110698-IV)

Vector Fabrics Joins ARM
Connected Community

Vector Fabrics recently announced it is
now a member of the ARM® Connected
Community®, the industry’s largest
ecosystem of ARM technology-based
products and services. As part of the ARM
Connected Community, Vector Fabrics
will gain access to a full range of resources
to help it market and deploy innovative
solutions that will enable developers to get
their ARM Powered® products to market
faster.

Mike Beunder, CEO at Vector Fabrics: “Many
of our customers have adopted multicore
ARM-based architectures and use our
vfEmbedded tool to optimize their software
applications for it. That’s why vfEmbedded
already provides support for the ARM
CortexTM-A series of multicore applications
processors, including the ARM NEONTM
technology. We’re excited to be working
more closely with ARM to ensure our tools
integrate well with the ARM architecture.”
The vfEmbedded multicore development
tool allows developers to unlock the
performance potential of the multicore
high-performance ARM Cortex-A
architectures. Optimizing software for
multicore processors by hand is simply
too complex, is error prone, takes too
much time, and won’t result in an optimal
implementation. VfEmbedded thoroughly
analyzes the program code, predicts
parallel performance and swiftly guides
the developer toward an optimal multicore
implementation that is free of errors.

The ARM Connected Community is a
global network of companies aligned to
provide a complete solution, from design
to manufacture and end use, for products
based on the ARM architecture. ARM
offers a variety of resources to Community
members, including promotional programs
and peer-networking opportunities that
enable a variety of ARM Partners to come
together to provide end-to-end customer
solutions. Visitors to the ARM Connected
Community have the ability to contact

12

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12-2011 elektor

QUASAR

Quasar Electronics Limited

PO Box 6935, Bishops Stortford
CM23 4WP, United Kingdom

Tel: 01279 467799
Fax: 01279 267799

E-mail: sales@quasarelectronics.com
Web: www.quasarelectronics.com

ronics

01279

All prices INCLUDE 20.0% VAT.

Postage & Packing Options (Up to IKg gross weight): UK Standard 3-7 Day
Delivery - £4.95; UK Mainland Next Day Delivery - £1 1 .95; Europe (EU) -
£1 0.95; Rest of World - £1 2.95 (up to 0.5Kg).

lOrder online for reduced price UK Postage!

Payment: We accept all major credit/debit cards. Make cheques/PO’s
payable to Quasar Electronics.

Please visit our online shop now for full details of over 500 kits, projects,
modules and publications. Discounts for bulk quantities.

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Secure Online Ordering Facilities • Full Product Listing, Descriptions & Photos • Kit Documentation & Software Downloads

Personal Download for I © Elektor

NEWS & NEW PRODUCTS

members directly through the website.
“The Connected Community is all about
companies working together to provide
the most complete solutions in the shortest
possible time. By joining the Community,
which now comprises more than 850
companies, Vector Fabrics increases the
large portfolio of skills, products and
services that are centered around the
ARM architecture, and currently available
to developers worldwide,” said Lori Kate
Smith, Sr. Manager Community Programs
for ARM.

Vector Fabrics’ vfEmbedded software
development tool addresses the hard
problem of partitioning and mapping
software onto heterogeneous multicore
SoC platforms. VfEmbedded lets you
model your embedded platform, then
takes you through the process of analyzing,
parallelizing, and implementing your code.
It is the only tool that gives you the precise
information you need to make sure that
the parallelized software works correctly
and has the highest performance on your
multicore machine.

http://cc.arm.coin

www.vectorfabrics.com/products/vfembedded

(110698-V)

Parallax: laser range
finder module

Designed in conjunction with Grand Idea
Studio, the Parallax Laser Range Finder (LRF)
Module is a distance-measuring instrument
that uses laser technology to calculate the
distance to a targeted object. The design
uses a Propeller processor, CMOS camera,
and laser diode to create a low-cost laser
range finder. Distance to a targeted object
is calculated by optical triangulation using
simple trigonometry between the centroid
of laser light, camera, and object.

KNX-RF Multi module for building automation

Radiocrafts AS now expand their product line with a new module complying with the
KNX-RF Multi specification. KNX is the only open international standard for Home and
Building Control, used in Smart Home, Building Automation and Building Management
Systems.

RC1 1 80-KNX2 is the world’s first RF module including a complete KNX-RF Multi protocol
stack. The KNX-RF Multi is an extension of the European Norm for building automation
adding redundancy and increased reliability. The main features of the new Multi
standard is; frequency agility by using up to 5 frequencies, fast link acknowledgement
of up to 64 receivers with automatic retransmission, and multi-hop repeaters extending
the range by two hops. Battery operated transmitters and receivers are also supported
by the new standard. The embedded protocol is backward
compatible with KNX-RF 1 .1 and KNX Ready, and can
be used for unidirectional and bidirectional
devices.

The new module is designed for
sensors, actuators and other home
and building automation equipment.

Due to its small size, easy to use interface,
complete embedded protocol and low power
consumption, it can easily be integrated into any product making a very cost efficient
solution.

Radiocrafts is a member of the KNX Association and has participated in the
development of the new standard. KNX is one of the leading standards for home and
building control. The interest for such systems is increasing, meeting the demands for
energy saving technology. Studies have shown up to 50% energy savings using KNX
technology.

Radiocrafts is also considered as one of the leaders in Wireless M-Bus technology,
and the new KNX product series gives the customers an easy transition to KNX with
compatible products. Interoperation between Wireless M-Bus and KNX-RF is also
possible using the new module.

The module operates in the 868 MHz band, using Listen Before Talk (LBT) and frequency
agility to reduce collisions. Up to 5 frequencies are scanned and automatically selected.
One receiver can be linked with up to 64 transmitters, enabling very large RF networks.
The fast acknowledge and retransmission feature ensure link reliability. Complete
repeater functionality is also built in the protocol stack, and can retransmit messages
in two hops. It can be used with S, A and E modes of installation. Among other features,
the module offer automatic battery supervision and signal strength information.

The new RC1 1 80-KNX2 is a surface-mounted high performance transceiver module
measuring only 1 2.7 x 25.4 x 3.3 mm. A UART interface is used for serial communication
and configuration. An antenna is connected directly to the RF pin. The RC1 1 80-KNX2
module is certified for operation under the European radio regulations for license-free
use. When used with quarter-wave antennas a line-of-sight range of 800 meter can
be achieved.

The module and Demo Kits are available now. The module is delivered on tape and reel
for volume production.

www.radiocrafts.com (110698-VI)

Features:

• Compact module with integrated CMOS
camera and laser system;

• Optimal measurement range of 6-48
inches (15-122 cm) with an accuracy
error <5%, average 3%;

• Maximum object detection distance of
approx. 8 feet (2.4 meters);

• Range finding sample rate of 1 Hz;

• Single row, 4-pin, 0.1 ” header for easy
connection to a host system.

The Laser Range Finder is priced at $1 29.99
and available direct from Parallax, or its
national distributors.

www.parallax.com, search 28044

(110698-VII)

M

Personal Download for I © Elektor

12-2011 elektor

DesignSpark chipKIT" Challenge

DesignSpark is the perfect environment for engineers to work together,
challenge each other to think outside the box and engage with fellow
designers from around the world. Participants of the DesignSpark chipKIT™
Challenge are encouraged to post photos/videos, summaries, and questions
about their projects, code, and PCB designs at www.chipkitchallenge.com
Register today and you could be selected for a chipKIT™ Community
Choice Award!

DJGILEH

Prizes include a $100 voucher for RS Components/Allied Electronics and
a free digital subscription to Circuit Cellar and Elektor magazines.
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ANDROID-TABLETS

Electronics designers are accustomed to developing their
systems from scratch or using development boards. An interesting
alternative is to use a tablet PC as an embedded device.

By Elbert Jan van Veldhuizen (The Netherlands)

Android
as a Develo

Using low-cost
tablet PCs in
embedded ap,

Tablet computers (PCs) running the Android
operating system are now available for
under 1 00 pounds/euros. They are packed
full of electronics and are visually attrac-
tive. Many functions that cost consider-
able effort to implement in an embedded
environment are standard features in tablet
computers. In this article we examine the
factors involved in using tablets in electron-
ics projects.

Hardware

What can you expect to find in a tablet com-
puter priced below 1 00 pounds/euros? To
start with, a nicely finished enclosure. A tab-
let is perfectly at home in you living room
or mounted on the dashboard of your car.
It can also be fitted on the front panel of an
enclosure to serve as a control panel with a
professional look, which is one of the major
potential uses.

A tablet has a backlit touchscreen display,
which make it an ideal platform for a user
interface, and in particular a graphic user
interface. The combination of a screen and
a touchpad allows you to create virtual
buttons (which can even be context sensi-
tive) and entry fields, and you can present
elaborate menu structures. Tablets are
also suitable for multimedia applications,
allowing you to display live imagery from
a camera (with or without an IP interface)
or play instruction videos. The displays of
the low-cost tablets have diagonal dimen-

sions of 7 to 1 0 inches (18 to 25 cm) and
resolutions of 800 x 480 to 1 024 x 600 pix-
els. Most low-cost models have a resistive
touchscreen, which allows only one touch
at a time, but this is generally good enough
for our purposes.

You might be thinking that tablets can
only be used as a sort of dumb terminal,
but this is by no means true. Even the low-
cost models have an ARM1 1 processor with
over 600 MIPS of computing power. This is
more than 1 0 to 1 00 times faster than the
microcontrollers we normally used in our
designs, and it means that tasks that need
a lot of processing power can run without
major problems on a tablet. Some exam-
ples include computations that are nor-
mally executed by a DSP, such as Fourier
transforms and filtering. Android is not a
real time operating system, so a tablet can-
not be used for real-time computations.
However, Android can handle near real
time tasks with response times in the sec-
onds range.

Programming Android apps was described
in detail in this year’s June 201 1 edition [1 ].
Android is a multitasking operating system,
which means that different applications for
different purposes can run in parallel.
Another important aspect of tablet com-
puters is Internet connectivity. All tablets
have a WiFi port for connecting to the Inter-
net. Various Internet apps are available for

Android devices, including a web server, an
FTP server and a variety of e-mail applica-
tions. These apps are able to run concur-
rently, including in the background. This
makes it easy to use an Internet connection
to view or download data remotely or to
control electronic devices remotely. Some
tablets (typically the more expensive mod-
els) also have a 3G mobile telecommunica-
tion port. This allows them to be used in
areas outside the range of a WiFi router, as
long as mobile phone coverage is available.
Tablets have integrated non-volatile (flash)
memory, and most of them also have a
micro-SD slot for memory expansion. This
allows up to 32 GB of memory (with cur-
rent devices) to be added. A typical appli-
cation for this is data logging. This amount
of memory is sufficient to store a year’s
worth of data at a data rate of 1 000 sam-
ples per second. This memory can also be
used for the previously mentioned multime-
dia applications.

Furthermore, most tablets have speak-
ers (as well as an audio out connector), a
microphone and a webcam built in. Tablets
can provide a regulated 5 V supply voltage
(from the USB port), taken from the inte-
grated (or replaceable) rechargeable bat-
tery. Although this is not the main reason
for using a tablet in an electronics project,
it’s a handy bonus.

Incidentally, tablets are not the only
Android devices worth considering. Android

16

Personal Download for I © Elektor

12-2011 elektor

ANDROID-TABLETS

Figure 1 . USB Micro B to Type A bus cable for use with a tablet operating in host mode.

smartphones are also available for under
150 pounds/euros. Although they have
smaller displays, they are equipped with 3G
functionality as standard. If 3G functional-
ity is more important than display size, an
Android smartphone is an excellent choice.
These smartphones also support Blue-
tooth wireless communication. The Ama-
rino project [2] uses the Bluetooth inter-
face to link an Arduino board to an Android
smartphone.

USB interface

Every tablet has a USB port, which appears
to be the logical way to connect the tablet
to external circuitry. In theory this is a sim-
ple task, but in practice it is full of pitfalls.
First of all, you need to realise that Android
tablets have evolved from Android mobile
phones. The USB port of a mobile phone
acts as a USB device (‘slave’ mode) and is
intended to be used for purposes such as
connecting the phone to a PC, and the USB
ports of Android tablets are also device
ports. This means that the connected cir-
cuitry must acts as a USB host (‘master’
mode), which generally requires a relatively
complex USB controller. However, many
tablets are able to switch the USB port to
host mode (which requires a special conver-
sion cable) or have a second port that oper-
ates in host mode. This port is intended to
be used for connecting a mouse, keyboard
or memory stick. Simple USB controllers

with a USB device port can also be con-
nected to this second port. Microchip pro-
vides code that can communicate with an
Android unit configured as a USB device.
A number of development boards are also
available [3].

In addition to the hardware, you need the
right driver software, which is not so easy.
Android does not have any standard sup-
port for USB devices other than those men-
tioned above. Although the most recent
versions of Androids (2.3.4 and 3.1) have
enhanced capabilities, using them is not
straightforward. In order to install the right
drivers, you must first install a modified ver-
sion of Android. This requires not only the
software (the ‘ROM’), but also root access
permission in the tablet. Apps that can pro-
vide this access are available for low-cost
tablets with a standard Android installa-
tion, but creating a new ROM is a task for
advanced users, and it is essential to have
all of the necessary drivers available. This
is a lot of work for a single project, but if a
particular tablet can be used in various pro-
jects, it may be worth considering.

Fortunately, it appears that this problem
will be remedied in the future. Google, the
maker of Android, is hard at work on ver-
sion 4 of Android, named Ice Cream Sand-
wich, which combines version 2 (for mobile
devices, including low-cost tablets) and ver-

sion 3 (for fancier tablets). One of Google’s
explicit goals is to allow Android devices to
communicate with many different types of
accessories. The software class ‘accessory’
[4] has been developed specifically for this
purpose. Although this functionality is
implemented in Android versions 2.3.4 and
3.1 , there is no standard support for it in the
ROM. The USB port is configured as a host
with the new class, which allows simple USB
controllers to be connected to the port. This
simplifies the connection of USB devices to
Android tablets. Support for this will prob-
ably be provided in the standard ROM ver-
sion, eliminating the need for upgrades.
Android version 4 is expected to be avail-
able in late 201 1 . The system requirements
for the new version exceed the capabilities
of current low-cost tablets. It will probably
take a while before low-cost tablets that
support this version become available, since
the prices of processors with sufficient com-
puting power are presently too high.

Architecture

If you use a tablet in an electronics project,
the place where you put the software that
provides the ‘intelligence’ (eitherthe tablet
or the external circuitry circuitry) is a signifi-
cant architectural issue. The advantage of
putting the intelligence in the tablet is that
you can work in a well defined program-
ming environment with an API that provides
direct access to the various components of

elektor 12-2011

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17

ANDROID-TABLETS

elopers

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Class Overview

Figure 2. The Android API is extensively
documented.

the tablet. The tablet also has high process-
ing power and large memory capacity. How-
ever, real-time applications are not possible.
The main reason for placing the intelligence
in the connected microcontroller is that the
application requires real-time control of the
circuitry and/or short response times.

In practice a hybrid solution will usually be
the most appropriate choice, with the app
that runs on the tablet handing the tasks
closely related to the peripheral devices of
the tablet, while the connected microcon-
troller provides direct control of the I/O.

Applications

To give you an idea of the realm of possibili-
ties, here we outline a number of potential

Figure 3. Using a tablet in a home
automation system.

applications and briefly describe the neces-
sary architectures:

• Data logger with configuration set-
tings entered over the GUI. The data
can viewed in graphic form on the GUI
or on a web page. The raw data can be
uploaded over the Web or via FTP. The
hardware requirement for this is an ADC
connected to the USB port. On the soft-
ware side, three apps would be necessary:
a web server and an FTP server (both of
which are available as standard apps), and
a user-written app for reading and storing
the data — plus a configuration settings
screen and graphic output.

• Telemetry from a (race) car, with live data
displayed on the GUI and 3G link capabil-
ity for reading out data in real time and
storing it on a flash memory card. This
requires a USB to OBD2 interface and
software to handle the interface, config-
uration settings, and data readout and
storage. If the data only needs to be read
out once per lap, a standard FTP server
app would be sufficient. If real-time or
near real-time readout is required, a new
app must be developed for this purpose
(perhaps based on a serial communica-
tion app).

• Home automation: controlling a solar
water heater and a central heating sys-
tem with the aid of weather forecasts on
the Web, with remote control via a web-
site and a GUI on the tablet. This requires
the same configuration as the data log-
ger mentioned above. An additional
feature here is that decisions regarding
how the solar water heater is used can
be taken based on information available
on the Web, such as the forecast hours
of sunshine and outdoor temperatures.
This requires writing a special app to
obtain this information, for example by
reading RSS feeds and extracting the
necessary data.

• Digital oscilloscope with settings and
waveform display on the GUI, and poten-
tially the ability to send oscillograms by
e-mail. The configuration described for
the data logger is necessary here as well. In
this case this case the majority of the intel-
ligence must be located in the connected
circuitry due to the required signal speeds.

• A coffee machine control panel that sends
an e-mail to the maintenance department
when the coffee needs to be refilled or
a problem occurs. Here the tablet can
serve as the heart of the system, but I/O
circuitry is necessary for controlling and
reading data from all of the components.

• A standard maintenance console. A tab-
let is very suitable for use as an external
console for troubleshooting, configu-
ration and maintenance. In its simplest
form it can communicate with the target
system over the USB port, using a termi-
nal emulator app on the tablet. This could
be used to view start-up messages or dis-
play the commands sent from the termi-
nal. A more complex option is a console
connected over a USB to JTAG converter.
Thanks to its low cost, a console of this
sort could kept on hand at every cus-
tomer site.

• Prototyping: the ease of writing apps
makes a tablet suitable for develop-
ing prototypes and proof-of-concept
designs quickly and efficiently. Thanks
to the large number of standard func-
tions in Android and the wealth of avail-
able apps, considerable functionality
can be deployed in a very short time.

Conclusion

Low-cost tablet computers can be effec-
tive, affordable and quickly implementable
components of electronic projects. In addi-
tion to a visually attractive design, they
have many readily accessible functions.
At present it takes a good deal of effort to
use the tablet’s USB port for connection to
external circuitry, but with the advent of
Android version 4 in the coming year this
will become easier. This will open the way
for a host of new applications.

(110667-I)

Internet Links

[1] www.elektor.com / 1 10265

[2] www.amarino-toolkit.net

[ 3 ] www.microchip.com/android

[ 4 ] http://developer.android.com/guide/
topics/usb/accessory.html

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19

AUDIO, VIDEO AND PHOTOGRAPHY

By Elbert Jan van Veldhuizen (The Netherlands)

With an Android tablet and a handful of hardware, you can
put together a remote control for a still camera for time-
lapse photography. It also allows the picture settings to be
configured from a web browser on a PC, which sends to
them to the tablet via the local WiFi network.

Time-lapse Photography with
an Android Tablet

Using a servo-operated
shutter release

The design described here can be used with
a still camera to cause it to take pictures at
regular intervals. If you make a film from
these pictures, the result is what is called a
time-lapse film in which hours or even days
are reduced to a few seconds. A similar pro-
ject for cameras with an external shutter
release input was published in a previous
edition of Elektor. The product described
here operates the camera button mechani-
cally using a servo of the sort used in RC
(remote controlled) models.

A special feature of this project is that an
inexpensive Android tablet (as described
elsewhere in this edition is used to provide
the GUI (graphic user interface) and enable
operation over the Internet. This article is
handy for learning more about the basic
building blocks for programming Android
tablets in embedded systems.

Design and user interface

This design is intended to operate a still

camera mechanically with the aid of an RC

servo, which makes it usable for all
types of still cameras. The author first tried
to access the shutter button leads of a com-
pact digital camera in order to operate the
camera electronically, but the components
are so small that it is virtually impossible to
do this without destroying the camera.

As can be seen in Figure 1 , the servo actu-
ates a lever with a plunger that presses
the shutter button on the camera. Other
mechanical arrangements for operating

Figure 1 . A prototype put together with a
few Meccano parts.

Figure 2. This circuit boosts the audio output signal to 5 V TTL level. A small 5-V AC power

adapter provides an adequate source of power.

20

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AUDIO, VIDEO AND PHOTOGRAPHY

the shutter button with a servo are also
conceivable.

As described in the article on Android
tablets elsewhere in this issue, it is pres-
ently not easy to use the USB port of an
Android tablet. In practical terms,
doing so would mean that for
each different type of tablet,
different instructions and soft-
ware would be necessary to
make the design described here
work properly. For this reason,
the author decided to use the
audio output to drive the servo.
The position of a servo is deter-
mined by pulses having a width
between 1 and 2 ms, or with
some servos between 0.5 and
1.75 ms. These pulses are repeated
every 20 ms. A pulse signal of this sort can
be generated directly using the tablet’s
audio output. The pulse amplitude at the
audio output is typically under 1 V, so this
signal needs to be converted to TTL level.
This is done by the circuit shown in Fig-
ure 2. Transistors T1 and T2 amplify the sig-
nal. As the zero level of the audio output sig-
nal is not necessary the same as the circuit
ground level (it may be floating), quasi-DC
coupling is provided by R1 and Cl . None of
the component values here is critical.

If no modifications to the software are nec-
essary, the program can be installed by cop-
ying the file t i me L a p s e . a p k (in the binary
folder of the zip file) to the tablet over the
USB port or from a flash memory card.
Sending the file to the tablet as an e-mail
attachment doesn’t work. The installation
program included with the tablet must be
used to install the program. Under Settings
/ Application settings / Unknown sources,
enable ‘Allow installation of non-market
applications’.

The circuit can be operated in two differ-
ent ways: either via a GUI on the tablet (see
Figure 3) or via an external web interface
(see Figure 4). On the GUI the number of
pictures and the time between pictures (in
seconds, with a minimum value 3 s) can be
best in the two text boxes. Three different
servo positions can be set with the three

sliders. The first position is with the camera
at rest; the second position is for pressing
the shutter button halfway for focussing;
and the third position is for taking a pic-
ture. Check to make sure that the slider set-
tings are right, since the position between
0.5 ms and 2 ms varies. For some servos this
is outside the working range, and they may
be damaged if they are driven with corre-
sponding pulses for a prolonged time.

The Phase button selects either positive or
negative pulse output. Depending on the
tablet, it may be necessary to invert the
pulses (this doesn’t matter for audio out-
put). Finally, the Start button starts and
stops a time-lapse sequence.

The application can also be operated over
the web. It listens to port 8090 at the IP
address of the tablet. Start by accessing the
tablet from your browser (on another com-
puter), for example by entering the address
ht t p: / / 1 9 2. 1 6 8. 1. 1 0 1: 8 0 9 0 / . The
current status will be shown. New values
can be entered in the form, and the time-
lapse sequence can be started and stopped
with the links. The logo on the web page (at
the top left) must be entered by the user by
placing a I o g o . j p g file in the / s c a r d /
webser ver_TL folder on the tablet. This
folder is created automatically when the
application is launched for the first time.

GUI programming

The basic aspects of programming Android
devices and the necessary resources were
described in the June 201 1 edition. The
author also used Eclipse [1 ] and the Android
Development Toolkit (ADT) [2] for this
purpose.

The GUI can be designed in a fully graphic
environment in Eclipse (see Figure 5). But-
tons, entry fields, text fields and so on can
be dragged from the toolbar to the virtual
tablet screen. This generates a file named
ma i n , x ml containing descriptions of all
of the elements, including their unique IDs.

The main routine is located in the T i me -
L a P S e A c t i v i t y . j a v a file (created by
Eclipse) under the class T i me L a p S e A c -
t i v i t y . This class provides the interac-

Figure 3. The GUI for camera operation
using the tablet.

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Figure 4. The accompanying web interface
on the computer monitor.

tion with the buttons. To access a button,
you have to link an object to the previously
mentioned ID as illustrated by the follow-
ing example:

Toggl eButton mtoggl eButtonl =

( Toggl eButton) f i ndVi ewByl d( R.

elektor 12-2011

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21

AUDIO, VIDEO AND PHOTOGRAPHY

Figure 5. The graphic design in Eclipse.

i d. toggl eButtonl) ;

Buttons can be used in two ways: actively
or passively. An object’s functions can be
used to read buttons and set values. This
is passive use. If a function of the class
should be actively invoked when a button
is pressed (or when the status changes),
this is done with mtoggl eButtonl.
setOnCI i c k L i st ener ( t hi s) .Only the
Start button is used actively in this program.
The time-lapse portion of the application
is a procedure that runs for a very long
time. This is not possible in the main class
(Ti meLapseActi vi ty) because this class
is responsible for handling the GUI. If this
class is busy, the GUI will not be refreshed,
with the result that the GUI will freeze solid.
Furthermore, Android terminates a class of
this sort if it does not respond within 5 sec-
onds because it assumes that the program
has crashed.

This is why Android provides the class
AsyncTask.lt runs in a separate thread
that is allowed to be constantly busy. This
thread may be launched only once, for
which reason it is not launched every time
a time-lapse sequence is started but instead
runs continuously, even if a time-lapse
sequence is not being executed.

Writing directly from AsyncTask to the
GUI elements is not allowed (it causes a

Figure 6. Interclass communication.

crash). The functions publ i shProgress
and onProgressUpdate are provided
for this purpose, publ i shProgress is
used to call onProgressUpdate from
AsyncTask. Writing to the GUI is only
allowed from the latter function. As only
this one function is available for driving all
of the buttons, a specific action is defined
in onProgressUpdate according to the
value of the first passed-in parameter (see
the code in onProgressUpdate and the
p p_ * variables).

The variables (I oop_st at e,l oop_count
and I oop del ay) are used for com-
munication to start or stop a time-lapse
sequence (communication in the opposite
direction of publ i shProgress). Figure 6
illustrates the communication between the
various classes.

The pulse waveform for the servo is stored
in an array, which is read out by the function

a u d i oTr a c k .

Web server

This project also uses the WiFi Internet link.
The status and settings can be viewed in a
web page, and the application can be oper-
ated from this page. There are essentially
three options for making all of this possible.
The first option is to use a separate web
server app, for which there are many free
downloadable versions available. This

allows files to be viewed in the file system.
This is a simple solution, but it has the draw-
back that it is limited to viewing the system;
it does not support operating the system.
It also requires frequent updating of the
HTML file, which in time will wear out the
flash memory.

At the other end of the spectrum there is
the option of using an extensive package
such as i-jetty [3]. This allows you to imple-
ment a versatile web server, but such an
extensive range of functions (and the asso-
ciated complexity) is not always necessary.
The author chose to use the open-source
software ‘android Webserver’ [4] for this
purpose, by including the code in the appli-
cation and modifying it where necessary.
The most significant modification is that
the web server still reads files from the file
system, which allows images such as I o g o .
j p g (as used here) or CSS files to be used
in the directory, with the exception of a
file with a user-defined name (in this case
i n d e x . h t ml ) that the program uses to
generate the web page on the fly. Because
the web server runs in a separate thread
and therefore does not have direct access
to the main routine Ti meLapseActi v -
i t y , the settings and status data are trans-
ferred using static variables (see the c mm_ *
variables). A static variable can be regarded

22

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AUDIO, VIDEO AND PHOTOGRAPHY

as a fixed memory location. Unlike normal
variables, which require a new variable to
be created for each object of a class, a static
variable is the same for all objects of a class,
and it can also be read and written from
another class. For this reason, static varia-
bles are called by their class name instead
of their object name.

The application is checked by analysing the
link. In the same manner as for HTML forms
(in GET mode), the variables are placed after
a question mark in the URL (URI). In this
case the URI i n d e x . h t ml ? a c t = s t a r t
starts the TimeLapse process. The same
approach can be used to set the number
of pictures and the delay, for example with
i ndex. html ? d e I =5. This is generated
automatically by the HTML FORM order.
Static variables are also used to communi-
cate these settings and orders. These vari-
ables are monitored inAsyncTask loop.
Another way to do this would be to use a
handler for this communication, for which
there are two options: a general handler or
a handler that is specified when the object
is created. However, that was not necessary
in this case.

Other functions

Here we can make a few general comments
regarding programming for Android.

It is user friendly to save the settings (pulse
widths, phase, number of pictures and
delay) in the program so that they do not
have to be entered again the next time the
program is launched. Android has specific
functions for this, comparable to the reg-

istry of MS Windows. These functions are
elements of the SharedPref erences
class. The parameter values are read when
the program starts up and are saved when
the program is stopped (by OnStop). These
settings are also retained when a new ver-
sion of the program is installed.

Current versions of Android do not include
an application manager, so it is not possi-
ble to see which applications are running
(regardless of whether they are running in
the foreground or the background). This
means that it’s easy to lose sight of your
application. If you then launch the appli-
cation again, you will end up with two
instances of the application running in par-
allel. This is especially problematical with
the application described in this article
because the web servers of both instances
will listen to the same port, making the
results unpredictable. Three provisions
have been incorporated in the program in
this connection. Firstly, the icon is displayed
on the status bar to make it easy to switch
back to the application from the status bar.
Functions for this purpose are provided in
the N o t i f i c a t i o n M a n a g e r class. Sec-
ondly, the setting androi d: I aunchMode
= “si ngl el nstance" is included in the
T i me L a p s e ma n i f e s t . x ml file to indi-
cate that a second instance of this program
is not allowed to run in parallel. Addition-
ally, the tablet should not be allowed to
enter screensaver mode, since that makes
the application unstable for some unknown
reason. This is prevented by the setting
androi d: keepScreenOn = "true".

Incidentally, there are rumours that this
problem will be mitigated in Android ver-
sion 4 and later.

When an application is installed in Android,
the user must give permission to grant the
application specific privileges for communi-
cating with various hardware and software
components of the tablet. For this program
this consists of access to the WiFi interface,
access to the flash memory card (for the
web server files), and access for blocking
the screen saver. These permissions must
be placed in the T i me L a p s e ma n i f e s t .
x ml file in the form of u s e s - p e r mi s -
s i o n s (take care to avoid the common
typo ‘user-permissions’)

Finally, you can dress up the program with
your own icons. This requires placing three
images in .png graphic format in the pro-
ject’s Res directory under drawable-hdpi,
drawable-mdpi and drawable-ldpi with
sizes of 72x72, 48x48 and 36x36 pixels
respectively.

All files for this project can be downloaded
free of charge from
www.elektor.com/ 1 1 0690.

(110690)

Internet Links

[1] http://eclipse.org/

[2] http://developer.android.com/sdk/
eclipse-adt.html

[ 3 ] http://code.google.eom/p/i-jetty/

[ 4 ] http://code.google.eom/p/
android-webserver/

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23

INFO & MARKET

The PCB Prototyper in Practice

The PCB Prototyper introduced a year ago by Elektor has now found a place in many labs and companies.
This machine allows users who do not have extensive experience with milling machines to mill single-sided
or double-sided PCBs quickly and easily. We visited a PCB Prototyper user to learn about their experience
with the machine.

By Harry Baggen

(Elektor Netherlands Editorial)

After Elektor presented the PCB Prototyper
in December 201 0, it didn’t take long for
the first orders to come in. The manufac-
turer (Colinbus) was already busy with the
first production batch, and after a while the
first units were delivered. The responses
from users proved to be extremely positive.
They hadn’t expected to be able to buy such
a precise, easy to use machine at a budget
price — after all, PCB milling machines are
usually much more expensive than the
3,500 euro (ex VAT) price tag of the PCB
Prototyper.

Here in the Elektor editorial office we were
wondering how this machine is used in
practice, so we arranged a visit to Avasto in
Oudewater (The Netherlands), a firm that

has been using a PCB Prototyper for a while.
Avasto is a multifaceted facility services
contractor that is active in construction
work, automation of production pro-
cesses, and the design and maintenance of
saunas, whirlpools and the like. Electronic
controllers are used in various projects,
often based on PLCs. However, this has also
involved more and more in-house develop-
ment of electronic devices in the last while.
Their latest product is a slide safety device
for swimming pools. This system provides
a signal at the top of the slide to indicate
when the next swimmer can jump onto the
slide. The swimmer can also press a button
to start a time measurement. After exiting
the slide, the swimmer presses a ‘Finish’
button in the catch basin, and the elapsed
time is displayed on a scoreboard. In addi-
tion to preventing blockage of the slide, this
system introduces a competitive element
that makes the slide more attractive.

Avasto developed the entire system in-
house and has already installed several sys-
tems. The system is approved by the Dutch
Keurmerkinstituut, which is responsible for
assessing and certifying product safety.
Co-owner Swen van Vrouwerff is a dyed-
in-the-wool technology buff who knows
absolutely everything about the projects
underway in his company, including their
mechanical, electrical and electronics
aspects. Nowadays the company is devel-
oping more and more electronics devices
in-house. When the PCB Prototyper was
presented in Elektor, he thought it would be
the perfect machine for his company, since
it would allow them to make PCBs quickly
for small product volumes. Although order-
ing small quantities of PCBs from a PCB
manufacturer is also possible, this takes
more time and is relatively expensive. Swen
is convinced that the investment will pay for
itself quickly.

24

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INFO & MARKET

Right now the PCB Prototyper is primarily
being used to produce PCBs for the slide
safety system described above. All of the
circuitry for the system, distributed over
nine PCBs, is housed in the robust enclo-
sure of the display unit. All of the PCBs are
made on the PCB Prototyper (photo 1). It
is controlled by a netbook located next to
the machine (photo 2). It’s worth men-
tioning that the user interface for the PCB
Prototyper and the structure of the entire
slide safety system were designed by two
young employees with intermediate voca-
tional school education. They told us that
the PCB Prototyper is very easy to use. After
spending a day trying it out, they were able
to use it properly and they managed to mill

top-quality PCBs. Producing a PCB with
roughly Eurocard dimensions takes around
half an hour. The machine stops automati-
cally when it’s time to change the drill bit or
milling cutter, so you don’t have to be there
all the time and you can do other jobs in the
meantime. Photo 3 shows the end result —
in this case a PCB for a display segment. The
PCBs from the machine are assembled and
then coated with a thick plastic film on the
copper side (photo 4) to protect the cop-
per against the effects of chlorine, which is
abundantly present near swimming pools.
Photo 5 illustrates the quality of the milled
tracks on the PCB. Finally, photo 6 shows
the enclosure of the slide safety system with
the fitted boards.

This is just one example of the many poten-
tial uses of the PCB Prototyper. Presently
Avasto produces mainly single-sided PCBs
for leaded components, but if the company
wishes to switch to SMDs in the future, the
PCB Prototyper can easily mill PCBs for them
as well. Furthermore, a variety of extension
options for the PCB Prototyper to make it
even more versatile will be available in the
near future.

( 110694 -I)

Internet Links

www.elektor.com/projects/

pcb-prototyper-(1 0061 9). 1 599728. lynkx

www.avasto.nl

elektor 12-2011

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25

READERS’ PROJECTS

Robusta:

a Satellite Built by Students

Picosatellites to promote

SDac

By Frederic Giamarchi (France)

rv^-4 ;

J

France is well known for its significant participation in the European space
programme and for its front-line space industry, but perhaps rather less so
for the training of its elite in this field. This is why in 2006 the National Centre

for Space Studies (CNES) launched Expresso: the first call for

projects to higher education. Montpellier 2 University applied with
their Robusta project — a cubesat picosatellite carrying a scientific
experiment of interest to the space community.

The

Robusta
( Radiation
On Bipolar
University Sat-
ellite Test Appli-
cation, Figure 1)
satellite [1] is going
to be launched by the
new European ‘Vega’ rocket
in late 201 1 . It will carry a scientific
experiment to measure deterioration in electronic components. It
will be placed into an elliptical orbit between 340 km and 1 ,450 km
at an inclination of 71 °. Throughout the whole flight, it will trans-
mit to the student ground station located on the campus of the
University of Montpellier measurement data for the components
being tested and the various status parameters. Subjected to the
various sources of radiation, solar wind, particles trapped in the
radiation belts, and cosmic rays, it will gradually fall back down
towards the Earth and after two years will disintegrate on entering
the atmosphere.

The Robusta satellite

This satellite has a real scientific mission: to measure the deteriora-
tion of electronic components based on bipolar transistors caused
by ionizing radiation. The components chosen fortesting are LM1 39
voltage comparators and LM1 24 voltage amplifiers, frequently-used
components on satellites. This deterioration is quantified by meas-
uring currents, voltages, temperature, and dose received (Figure 2).
This dose corresponds to the absorbed radiation per unit of mass.
The results will then be compared with those obtained by a ground
test method devised by the researchers at Montpellier University’s
IES laboratory (IES stands for Institut d’Electronique du Sud, Southern
Electronics Institute) [3][4].

The duration of the mission is fixed at two years. The data will be
measured at least every^ 1 2 hours. They will then be transmitted
to the Montpellier campus ground station using an amateur radio
protocol and frequencies. Transmission will take place in broadcast
mode, i.e. continuous every minute, whether or not the satellite is
in a window of visibility for the ground station.

A crucial point for the success of the mission is power manage-

Note. Readers’ Projects are reproduced based on information supplied by the author(s) only.

The use ofElektor style schematics and other illustrations in this article does not imply the project having passed Elektor Labs for replication to verify claimed operation.

26

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12-2011 elektor

READERS’ PROJECTS

ment. The satellite will be powered by Saft Li-Ion batteries, which
will be recharged by special triple-junction space solar cells with
27 % efficiency.

Internal structure

The mechanical structure, the dimensions and positioning of the
electronics boards, and the aspects of the launch system via a
p-pod (Figure 3) are being taken care of by the CMP ( Genie Mecan-
iqueetProductique, Mechanical & production Engineering) and CEII
( Genie Electrique et Informatique Industrielle , Electrical & Industrial
Computing Engineering) sections of NTmes Polytechnic. The power
supply board and power management for the battery and solar cells
sub-system is also being dealt with by NTmes Polytechnic’s GEII sec-
tion. The controller board sub-system, which manages the com-
mands between boards and stores the measurement data, and the
microcontroller programming and test receiver elements are being
operated by departments within Polytech’Montpellier. The experi-
menfboard sub-system, which includes the components under test
and the dose and temperature sensors, is being designed by EEA
(Electronics, Electrical Engineering, and Automation) degree and
Master’s students in the Faculty of Science. The radio communica-
tion board and ground station sub-systems specifically are being
handled by Microwave students.

The components and materials used in this project are commercial
components that are not hardened, apart from certain ones like the
battery and solar cells. A rigorous radiation quality assurance pro-
cess has been operated to minimize the risks associated with their
exposure to radiation as far as possible. The project will be consid-
ered a success if it operates for more than a year.

Mechanical structure

The mechanical structure has been designed and machined out of
a solid block so as to form a single piece (Figure 4). The structure
is made from aluminium 6061 , which has stable density in a space
environment. The various elements of the satellite, solar cells, PCBs,
screws, connectors, wires, etc. have all been designed and dimen-
sioned as the project has progressed. It’s taken constant interac-
tion between the different teams for various the parts to keep the
various measuring elements up to date with developments in the
various corrections validated.

Figure 1 . CAD model of the Robusta satellite,
(source: RobustaCom)

Figure 2. Example of modelling for calculating the dose absorbed
by a component in Robusta using the FASTRAD software.

(source: RobustaCom)

Cubesat

‘Cubesat’ satellites are part of an educational programme put in
place in 2000 by California Polytechnic University (CalPoly) [2], the
aim of which is to offer students concrete experience and in-depth
knowledge in relation to research and the aerospace industry. A
cubesat is a satellite in the form of a 1 0 cm cube, weighing a maxi-
mum of 1 kg and having a maximum power of 1 W. It consists of
a useful load referred to as the payload, corresponding to the on-

board experiment, and a platform comprising the various electron-
ics boards allowing control of the experiment, communication with
the Earth, and power management. The whole thing represents the
simply a very small equivalent of a conventional larger satellite, sub-
ject to the same stresses, with thermal shocks, extreme vibration at
blast-off, radiation, and the vacuum of space.

elektor 12-2011

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27

READERS’ PROJECTS

Figure 3. 3D exploded model of a p-pod. (source: CubeSat Project)

Power board

The power board recharges the battery and distributes the different
voltage rails needed for the various sub-systems. It also includes the
system required for triggering deployment of the antennas once in
orbit. The component ratings chosen allow a significant margin in
terms of the power required. The battery charging system allows
for the temperature-dependent variation in the solar cell voltage,
as well as their deterioration over time. Three rails are provided:
8 V for the amplifier used to transmit the data back to Earth, 6 V for
the logic circuits, and -5 V for the components under test. The six
faces carrying solar cells will be subjected to the sun’s rays in a ran-
dom order, depending on the rotation of the satellite. It has been
decided to measure the voltage and current from these six faces in
order to verify proper charging of the battery and implicitly meas-
ure the satellite’s rotation. An l 2 C bus was chosen by the students
for dialoguing between the power board and the controller board.

Experiment board

The electronic circuitry for the experiment board had to be very

Figure 4. 3D exploded model of the satellite, (source: RobustaCom)

thoroughly designed and tested. Each of the integrated circuits
under test (LM1 24 and LM1 39) includes eight elements, for which
currents, voltages, temperatures, and doses have to be measured.
So it was necessary to find an architecture based on analogue
switches driven by the microcontroller in order to multiplex the
measurements made at the various pins of the devices (Figure 5).
The students had to choose a bus that would allow managing the
large number of addresses allocated to the switches, and in so doing
learnt a lot about l 2 C and SPI buses.

Apart from the power board, the other boards each have a
PIC1 8F4680, an ADC interface and an anti-latchup system (protect-
ing the microcontrollers against short-circuits generated by ioniz-
ing particles).

Controller board

The brains of the satellite: its function is to organize the tasks of the
other boards. It manages the dialogue with the other boards and
it is responsible for managing the power available. For example, it
inhibits communication with the ground station while an experi-

Composants

Testes

2x LM124
2x LM139

Interrupteurs

Bus SPI

Metrologie de I’environnement

Dosimetrie

Dosimetrie OSL

Temperature

Capteur de temperature 1

Capteur de temperature 2

Systeme

de

mesure

Microcontroleur PIC18F4680

Software

I/O

Memoire

Vers carte
controleur
Bus CAN

110493 - 11

I

Antenne

1

Carte

Experience

Carte

Communication

■ 1

Bus CAN

1 1

Support Electrique

Carte

Puissance

Bus I2C

Carte

Controleur

Figure 5. Block diagram of the experiment board,
(source: RobustaCom)

Figure 6. Interconnection of the four boards
using l 2 C interface and CAN bus.

28

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READERS’ PROJECTS

100% student

The Robusta satellite and dedicated ground station have been
entirely designed and produced by the students from the vari-
ous courses at the Montpellier 2 University: NTmes Polytechnic,
Polytech’Montpellier engineering college, and the EEA (electronics,
electrical engineering, automation) degree and master’s courses
in the Faculty of Science. This project in partnership with the CNES
is also being supported by major manufacturers in the electronics
sector.

tions and making the project information accessible for the media.
The satellite has to be conceived, produced, and tested by the stu-
dents, guided by educators who are experts in the field concerned,
and always under the control of the CNES. The students are also re-
sponsible for the project management.

This project represents real experience of an industrial nature, but on
a scale that remains accessible to students by virtue of its duration,
cost, and technical level. Robusta, as a system, makes it possible

Several major educational themes can be identified within this pro-
ject: the system design and associated project management, the
mechanical structure, the environmental tests, and the sub-systems
involving several fields within the EEA: power management, payload,
controller board, radio communication board, and the associated
ground station. And lastly, there is an element involving communica-

tor college students from 2 nd year degree to PhD level to develop
sophisticated engineering prototypes and to improve their sense
of communication, while discovering the world of space. They are
deeply committed right from defining the mission to exploiting the
measurement data, through all the phases of design, component
sourcing, production of prototypes, and testing.

ment is in progress, as these two actions are too power-hungry.

In the course of the inter-sub-system meetings, it was decided to
use a CAN bus for the communication between the various sub-
systems (Figure 6). But as part of the prototype design process,
the students have been able to develop their own data exchange
protocol. As there are such a large number of messages to be sent
to the other boards, a Petri net has been used to avoid jams and
losing messages, and to correctly handle the imposed restrictions.

Radio board

For the radio communication sub-system, the students have paid
due attention to the selection of the frequency band allocated for an
application. After studying various transmission/reception architec-
tures, they opted for a system using two separate frequencies in the
radio amateur bands: 435.325 MHz for transmission to the ground
station and 1 45.95 MHz for receiving the remote commands. The
choice of components, in particular the amplifiers, was made in

direct consultation with the ground station sub-system students,
in accordance with the link budget. In addition to learning a great
deal about the problems specific to using radio frequencies, they
were also called up to implement signal processing processes when
choosing the type of modulation and demodulation. And simula-
tion has not been overlooked, particularly for the satellite antennas,
which were fully simulated using CST Microwave Studio, a special
professional microwave application.

Ground station

The ground station is an integral part of any space mission and is
vital for it to function properly. It becomes the sole communication
interface possible once the satellite is in orbit. Thus it makes it pos-
sible to receive all the experimental data and the flight parameters
(telemetry), as well as to send remote commands for modifying the
experimental protocol or the behaviour of the satellite (for exam-
ple, manage the power supply, activate or disable certain sections).

Expresso

The Toulouse Space Centre (CST) which comes under the CNES offers
students an opportunity to gain concrete experience in the field of
orbital systems. This is also the occasion to test out new technolo-
gies and to perform scientific experiments for the space community

at minimal cost. To support the project, the CNES is offering financial
resources and is making available a project co-ordinator and experts
from the CST for the thermal analysis, the solar cells, vibration test-
ing, frequency use permissions, etc.

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29

READERS’ PROJECTS

Figure 7. The Robusta ground station,
(source: RobustaCom)

Figure 8. The Vega rocket,
(source: ESA)

The Robusta ground sta-
tion (Figure 7) is con-
structed around ama-
teur radio hardware.
The central element
in its architecture is a
transceiver that allows
modulation/demodula-
tion of AFSK signals, in
the 430 MHz band for
the telemetry and in
the 144 MHz band for
the remote commands.
Two motorized anten-
nas establish the link
with the satellite. A PC
manages the motori-
zation of these anten-
nas, as well as sending
the remote commands
and the reception of
the telemetry. All this
ground station soft-
ware has either been
developed internally or
comes from the world
of ‘open source’ — start-
ing with the Ubuntu
operating system on the
ground station PC. This
means we can adapt the
software to our specific
needs and upgrade it
over time with no par-
ticular restrictions.

The Vega launch
vehicle

Following a call for
applications, the
Robusta satellite was
chosen to be put into
orbit along with eight

others during the Vega rocket’s (Figure 8) qualification flight.
The Vega project should make it possible to put small satellites -
between 300 and 2,000 kg — into low or polar orbits. This will be a
first for this launch vehicle which will blast off from the Kourou space
base in French Guiana in late 201 1 .

In all, nine cubesats will be released from the launcher at the same
time as the main payload, a scientific satellite called LARES System
along with the educational mini-satellite ALMASat.

(110493)

Internet Links & References

[1 ] Project Robusta: www.ies.univ-montp2.fr/robusta/

[2] Cubesat by California Polytechnic State University:
http://polysat.calpoly.edu/

[3] J. Boch, “Estimation of Low Dose Rate Degradation on Bipolar Lin-
ear Integrated Circuits Using Switching Experiments”, IEEE Trans.
Nuclear Science, vol. 52, pp. 2626-2621 , December 2005.

[4] J. R. Vaille, F. Ravotti, P. Garcia, M. Glaser, S. Matias, K. Idri, J. Boch,
E. Lorfevre, P.J. McNulty, F. Saigne, L. Dusseau, “Online dosimetry
based on optically stimulated luminescence materials”

IEEE Trans, on Nuclear Science, vol. 52, Issue 6, December 2005
pp. 2578-2582.

The space adventure continues with Friends and Ristretto

Robusta, Expresso, Friends, Ristretto — no, these aren’t terms from
some galactic coffee bar, but rather the names of student projects
for conquering space. Small student satellites of increasing size —
this is what Montpellier 2 University is offering us, in collaboration
with the CNES, the ESA, and the Baumann University in Moscow.

To meet these new challenges, Montpellier 2 University will shortly
be setting up a university space centre named SOLARIUM (Sys-
temes Orbitaux Lies auxActivites de Recherche Interdisciplinaires de
IVniversite Montpellier 2), with support from the Van Allen founda-
tion — the first in France to exploit the potential of small satellites

30

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EMBEDDED LINUX

XPort your Ideas
to the Web

More and more microcontroller systems
come with an Ethernet port. At Lantronix
they took the opposite approach: XPort Pro is
a network interface module with an integrated
microcontroller. This article gives you some
pointers for setting up a software development
environment and presents three example applications.

By Kevin Petit (France) [kpet@free.fr]

From the hardware perspective, the XPort
Pro module [1 ] is a Freescale MCF5483 Cold-
fire microcontroller. It operates at 1 66 MHz,
has a built-in Ethernet interface and an
encryption accelerator, is equipped with
8 MB of RAM and 1 6 MB of flash memory,
and is housed in an RJ45 enclosure measur-
ing 3.3 x 1 .6 x 1 .4 mm. It has five I/O pins,
with two of them reserved forTxD and RxD,
while the other three can be used for RTS,
CTS and DTR on the serial port or for gen-
eral-purpose I/O under the monikers CPI ,
CP2 and CP3. All of this runs under Linux, or
more precisely, under uCLinux (pronounced
‘you see Linux’).

You don’t need to make a PCB in order to
get acquainted with the XPort Pro module
- you can use a demo board from Lantro-
nix (Photo 1 ) or the XPort (Pro) to bread-
board interface described in our Embed-
ded Guide 2010 supplement, which was
included in last year’s December issue.

If you’re totally new to installing and con-
figuring a Linux SDK, you may quickly find
yourself wondering where to turn next, so
we should first explain what a Linux SDK is.
Usually it’s a collection of source code files,
including the Linux core, a C library, applica-
tions and so on, along with a set of rules for
putting everything together - which take
the form of what is called a make file. There
are several other essential ingredients, such
as the compiler chain, a utility for creating
images, and so on. After all this hotchpotch
has been installed and configured properly,
it’s very easy to use it to develop all sorts of

software for anything you may dream up.
However, it’s a good idea to bear in mind
that no SDK is entirely foolproof (don’t say
we didn’t warn you!). Usually there are a lot
of settings that need to be dealt with, espe-
cially when you’re just getting started. If
all this is making you feel a bit nervous, we
hope that the pointers below will put your
mind at ease (more or less).

SDK installation

The Lantronix SDK only runs under Linux.
However, it’s possible to run Linux on a Win-
dows machine in a virtual PC environment.
This is a good solution, not only for devoted
Windows users but also for everyone who is
willing to sacrifice a bit of performance for
easier installation. The downloads for this
are available at [2], although you may find
a bit of explanation necessary.

If you prefer not to take the virtual machine
approach, you will have to install the SDK
yourself. There are two options here: you
can burn the ISO image of the SDK on a CD,
or you can mount the image (to use the
Linux jargon). The author chose the second
option.

Start by creating a directory to hold the
image, for example with the mkdir / mnt/
iso command (note that this requires you to
be the root user). Now you can mount the
image with the command mount -o loop /
path/to/iso/image / mnt/iso. Next, create a
directory for installing the SDK, for example
by typing mkdir ~/xport-sdk. Then type
cd ~/xport-sdk to go to this directory, fol-

lowed by /mnt/iso/install.sh to launch the
installation script.

If your Linux distribution is based on Debian
or Red Hat, things should be very easy from
this point onward. Otherwise, such as in
the author’s case, you must first copy the
entire CD to a new folder of your choice.
This is because you need to modify the
script file install. sh, and no matter how
hard you try, you can’t modify a file on a CD.
Install. sh calls another script named scripts/
host_depend.sh, which installs the software
required for the SDK. However, this doesn’t
work with distributions that use the RPM
or DPKG package manager, so you have
to comment out the lines in install. sh that
call host_depend.sh by placing a number
sign (#) at the start of each of these lines.
In SDK version 2. 0.0.0, these are lines 167
to 171 (inclusive). All of these lines must
be commented out with a number sign at
the start. Now you can run the installation.
If you choose this method, you will have to
install all of the software necessary for the
SDK yourself, guided by the error messages
displayed during the installation process.
After completing the installation, you can
unmount the image with umount /mnt/iso.

Elektor patch

Once the SDK is installed, you can add the
demo applications for this article. They are
intended to form part of the image, and
they should be located in /home /elektor.
Start by downloading the zip file from the
Elektor website [3]. Extract it in the folder
of your choice (such as /tmp). This creates

32

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EMBEDDED LINUX

A software development environment for
XPort Pro, including three example applications

a folder named Elektor-XPort. Open this
folder and type the command ,/elektor_
install. sh dossier_d'installation_du_SDK
(“SDK installation file”). If everything goes
well, you will see the message ‘SUCCESS’.

Partitioning flash memory

You can partition the flash memory of the
XPort module using one of the schemes
defined by Lantronix, or using your own
scheme if you know what you’re doing. The
author chose the ‘kernel + romfs + JFFS2’
option. What all this means is explained in
the documentation for the SDK. One par-
tition contains the core image with rootfs
in romfs , where ‘fs’ stands for ‘file system’.
Rootfs is the space where system files are
stored, similar to the C: volume on a Win-
dows machine. Romfs is a read-only file
system that is used to prevent files from
becoming corrupted, since viruses cannot
burrow into files that cannot be modified
or overwritten. The third partition is for-
matted as JFFS2. JFFS2 is a file system spe-
cifically designed for flash memory, and you
can use it to store whatever you wish. The
advantage of this arrangement is that you
can leave data undisturbed in the JFFS2 par-
tition when you download new firmware to
flash memory, which is certainly practical.

Configuring and using the SDK

Before you can create an image for down-
loading to the XPort Pro module, you
must configure the SDK. Start by open-
ing the directory where you installed the
SDK. In this directory, issue the command
source env_m68k-uclinux, which config-
ures the environment variables so the SDK
will work properly. You must enter this com-
mand every time you open a new terminal
session. Then start the configuration pro-
cess with make menuconfig. Before you
see the main menu, you have to answer
a series of questions. Choose the default
answer in each case, and press the Enter
key. After this you will see the actual menu.
Select the first submenu, Vendor /Product
Selection, and verify that the vendor is set
to Lantronix and the Lantronix product is
set to XPort_Pro. You can also select a pro-
file to be used. A profile consists of a set
of parameters for the Linux core, uCLinux,
and the applications to be installed with

them. A good choice here (the author’s
choice) is the DEVELOPMENT profile. The
various options belonging to each profile
are documented in 900-548c_Linux_SDI<_
UG.pdf, which is located in the SDK docu-
mentation folder.

Press Exit to return to the main menu, and
confirm with Enter. Now select the second
menu, /Library /Defaults Selection, and use
the space bar to select Customize Kernel Set-
tings and Customize Application /Library Set-
tings. Finish off with Exit and Enter twice
in succession. Answer Yes to the question
whether you wish to save the configuration.

A second configuration menu for the Linux
core will open a few seconds later. Select
Processor Type and features and set the Lant-
ronix CP Manager option to General Purpose
I/O. This allows three of the five I/O lines to
be used for your own purposes, as previ-
ously mentioned. By default, two of them
are used by the serial port driver for RTS and
CTS. If you use the Lantronix demo card, be
sure to remove all jumpers from JP6 except
numbers 1 and 7. Tick Reclaim page before
process loading to reduce memory fragmen-
tation. Now you can exit the menu as previ-
ously described, and of course you should
save the configuration again.

Next you come to the third and final menu.
Here you only have to close the menu, but

once again you must save the configuration
when asked.

Now you can issue the make command to
start compilation. This takes a while, so it’s
a good opportunity to go for a coffee break.
After you get back, you should find a num-
ber of images in the linux/images folder of
the SDK, ready for downloading to flash
memory. The most important items here
are the image.bin file and the romfs file
system.

To load an image into the XPort Pro module,
you must use a TFTP server. This is not the
place to delve into the details of configur-

ing a TFTP server for all possible Linux dis-
tributions, but Google can be helpful in this
regard. The server must be configured so
that the root points to linux/ images in the
SDK. The author can strongly recommend
tftpd-hpa. Other servers caused a few prob-
lems in combination with the XPort module,
but you shouldn’t encounter anything truly
insurmountable.

Open the XPort!

At this point you should be fully ready to
flash an image via the TFTP server. If you’re
in a hurry or you don’t have the time or the
inclination to install the SDK yourself, you
can download a ready-to-use image from
the Elektorweb page for this project [3].

elektor 12-2011

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33

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Figure 1 . Boot loader configuration.

Now we get down to brass tacks with a
few practical examples (at last!). First let’s
configure the boot loader dBug. Using your
favourite terminal emulator program (set
to 115,000 baud, 8 data bits, 1 stop bit,
no parity and no flow control), establish a
serial connection to the XPort module Then
switch on power to the card. Now you have
to be fast: you must press a key within three
seconds to bring up the command prompt
for the boot loader. If you manage this,
you will see dBUG> on the screen. You can
use the help command to view help text,
show to display the current configuration,
and set to configure the various configura-
tion options. Figure 1 shows our chosen
configuration.

set watchdog off: We don’t use the
watchdog.

set silentboot off: Silent boot starts up
faster, but you have to hit Ctrl X light-
ning fast to access the boot loader menu,
and that’s not helpful in a development
environment.

set romfs_flash on: The romfs file system
is not loaded into RAM, but instead runs

directly from flash memory. This frees up a
lot of working memory, although at least in
theory it slows things down a bit. However,
the author didn’t notice any difference for
the applications described below.

set autoboot flash: We want to boot auto-
matically from flash memory. Another
option would be to boot from the network.

set server ip_server_TFTP: Sets the IP
address of the TFTP server, for example in
the form 192.168.0.1.

set client ip_client: The boot loader needs
a valid IP address for all transactions on the
network. This address is not related to the
address that is used after Linux is launched.

set netmask uw_netwerk_masker: If you

don’t know what to enter here, there’s a
good chance that ‘255.255.255.0’ will get
you what you want (most of the time).

set filename image.bin: The file we want to
load into flash memory is named image.bin.
set kcl rootfstype=romfs: This tells the
Linux core that rootfs is of type romfs.

After making these configuration settings,
you can issue the command dnfl (which
stands for ‘download from network and
flash’). This should start downloading
image.bin. If it doesn’t, you should check
whether your TFTP server is working prop-
erly - for example, by using a TFTP client
on another computer in the network. Once
the download is complete, you will be asked
whether you wish to clear flash memory
(which means overwriting it); answer Yes.
The actual flashing starts after this. You will
receive a message if the process completes
without errors. In this case, press the Reset
button on the demo board. In response,
you will see that Linux is launched, and a
short while later the command prompt will
appear. Give yourself a pat on the back - the
hard part is done, and now it’s time to have
fun. Let’s see what neat things you can do
with this system.

The old standby: blinking LEDs

Lantronix supplies a utility called cpm
(for ‘Configurable Pin Manager’) that can
be used to manage the GPIO pins of the
XPort Pro module. This program expects
to receive an input file containing the con-
figuration of the three I/O pins. The proper
syntax is described in the Lantronix docu-
mentation, although you can also get good
idea of this by examining the included file.
This small demo program uses a shell script
that calls the Lantronix cpm utility for the
I/O pins. If you don’t know what a shell
script is, don’t worry - it’s simply a text file
with a list of commands to be executed in
sequence. If you want to see anything with
this demo, you need to connect a pair of
LEDs to the CPI and CP2 lines. Then use the
cd command to go to the folder /home/ele-
ktor/ledcpm and enter ./led-blink.sh. You
should see the LEDs blinking alternately.

A touch of Internet

Making a pair of LEDs flash is good fun, but
it’s not really world news. We have a built-
in network link in the XPort, and it would be
a sin and a shame to not use it, so we need
some sort of Web application. Let’s do it!
For this purpose we use Boa, a lightweight
web server included with the SDK. It has to
be provided with a configuration file named
boa.conf. The syntax rules for this file can be

FORM_GPIOCP Won '
FOP,M_GP'IOCP2 = "on'
F0RM_GPIOCP3="on'
Turning CPI on.
Turning CP2 on.
Turning CP3 on.

State of CPI
State of CF2
State of CPS

Submit

O

□

□

Figure 2. Screenshot of the web application that controls the GPIO ports.

34

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EMBEDDED LINUX

found on the Boa website [4]. After modify-
ing this file as appropriate, you can launch
the server with the command boa -c rep_
config, where rep_config is the name of
the folder containing the boa.conf file. This
application allows the I/O pins to be set and
read from a web page (see Figure 2). The
author used CGI [5] to enable the XPort
module to do something. The XPort mod-
ule does not support languages such as
Perl or Python that can be used to gener-
ate CGI scripts. The author was not inter-
ested in writing a C program for this specific
purpose, and manually processing HTTP
requests was not a desirable option. After
nosing around on the Web, he found ProCGI
[6], a small C program that processes HTTP
requests and allows users to configure varia-
bles that can be used directly in shell scripts,
which as already mentioned are lists of exe-
cutable commands. However, a few modifi-
cations to ProCGI were necessary to enable
it to work with the command interpreter in
the XPort module.

That’s enough theory for now; let’s get the
application up and running. Before you
launch the web server, the XPort module
must be given an IP address. If there is a
DHCP server on the network, this has prob-
ably already happened. You can verify this
with the ifconfig command. Otherwise you
will have to assign an address manually using
the command ifconfig ethO up ip_adres.
Then go to the folder /home/elektor/webgpio
and enter boa -c . (note that the space and
the point must be entered as shown). Voila:
the web server is up and running.

You can connect to it by entering http://ip_
van_XPort in the address bar of any desired
web browser. Set the desired levels on the
outputs and click the button. The script in
the XPort module decodes the request and
uses the cpm utility to configure the out-
puts. Cool? Cool! And speaking of cool, we
have something else for you.

Web-based temperature logging

To show what this little module can do
despite its limitations, the author decided
to do something a bit more complicated:
connect a temperature sensor to the XPort
module and display a plot of temperature
versus time on a browser. The architecture
of this application is shown in Figure 3. The

□ your applications

In this article we dispense with the usual ‘Hello World’ introduction, so we thought it would
be a good idea to mention a few aspects of compiling applications for the XPort module.
Applications can be integrated into the SDK, but they can also be compiled from a sepa-
rate directory. If you want to have your applications be included in the image.bin file, you
must choose the SDK option Regardless of you choice, there’s no getting around the task
of generating a make file. A handy tool for this is available at [7], and you can draw inspira-
tion from the examples there. The compiler can be invoked directly (m68k-uclinux-gcc)
for very simple applications such as ‘Hello World’, but for anything else this method is very
tedious, which is why we use make files.

Figure 3. Architecture of the webtemp application.

CLinux: can we live without an MMU?

In virtually every computer a memory management unit (MMU) controls traffic to and from
the memory. The absence of an MMU in the XPort Pro module creates limitations and forc-
es us to use uCLinux - a Linux distribution specifically created for systems without an MMU.

Some functions that are included in the standard package of ‘normal’ Linux are completely
absent under uCLinux or exhibit abominable performance (fork and mmap). Another major
irritation, especially in a development environment, is the absence of memory protection.
There is no strict partitioning of memory areas for different processes, so if your program
crashes, it may take the entire system down with it. For this reason, you must keep a close
lookout for potential problems such as null pointers and other memory-related bugs.

elektor 12-2011

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35

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The La ntronix virtual machine

After downloading the compressed file for the virtual machine from
the website [2], extract it in a folder of your choice. Then install the
program VMware Player, which you can find at [8]. Launch VMware
Player and open the .vmxfile from Lantronix. The program asks
whether you have relocated or copied the virtual machine; select the
latter option. In response, the virtual machine starts up and requests
your user ID. The password is ‘PASS’.

The default keyboard configuration is QWERTY, which is OK for most
English-speaking users. If you wish to change it, open the configura-
tion dialog under System -» Preferences —> Keyboard. You can add the

desired keyboard layout on the Layout tab. Then use Move Up to put
it at the top of the list. Click Close to close this window. That takes
care of the keyboard.

To get started, launch a terminal session via Applications Accesso-
ries -» Terminal. The SDK is located in /home/lantronix/linuxsdl<.

One final remark: if you configure the TFTP server, remember that it
must be installed on the virtual machine, so you must use the IP ad-
dress of the virtual machine to allow it to establish a connection to
the server. Have fun!

Figure 4. Screenshot of the webtemp application.

sensor is a TMP1 02, which is connected to
the XPort Pro over an l 2 C interface (SDA to
CPI and SCL to CP3). The author originally
planned to use rrdtool to generate the chart,
but due to some of the limitations of the
XPort module he was not able to get it to
work reliably. He then realised that it would
be better to leave chart generation to the
client, which in this case is the web browser.
At the XPort end there is a C program that
simulates an l 2 C bus interface on the I/O
pins of the XPort module. The cpm utility
does not provide enough performance for
this task, so the author used the Lantronix
libcp library instead. Temperature readings
are written to a file at regular intervals. A
web server (Boa) runs on the XPort module.
At the PC end there is a mixture of HTML,
CSS and Javascript. The Javascript portion
use AJAX to retrieve data from the server
running on the XPort module. The server
calls a small C program that converts the
data file to JSON (a format used for exchang-
ing data over the Web) and returns the con-
verted data. After this, Javascript calls the
Plot library, which generates a plot of tem-
perature versus time. A button on the web
page allows the plot to be updated man-
ually, and another button enables auto-
matic updating at 1 -second intervals (see
Figure 4).

All of the source code is reasonably well
commented, and as usual it can be down-
loaded from the Elektor web page for this
project [3J. To run this application, open
the directory /home/elektor/webtemp. Type
boa -c . & to launch the web server, then

type tmp102 -q -F /tmp/temp.dat -nO to

initiate communication with the sensor.
After this, point your favourite browser
to http://ip_van_XPort and click one of the
buttons.

This article, although far from exhaustive,

is intended to get you off to a running start
with the XPort Pro module. Despite its limi-
tations, you can do a lot with this module.
We hope our efforts stimulate you to start
XPorting your own ideas.

(100388-I)

Web links

[1] www.lantronix.com/device-networking/embedded-device-servers/xport-pro.html

[2] http://forums.lantronix.com/forumdisplay.php?f=20

[3] www.elektor.com/ 100388

[4] www.boa.org/documentation/boa-2.html#ss2.3

[5] http://en.wikipedia.org/wiki/Common_Gateway_lnterface

[6] www.fpx.de/fp/Software/ProcCGI.html

[7] www.makelinux.net/make3/

[8] http://downloads.vmware.eom/d/info/desktop_downloads/vmware_player/3_0

36

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12-2011 elektor

Elektor Academy Webinars in partnership
with element14

Elektor Academy and elements have teamed up to bring you a series of exclusive webinars covering blockbuster
projects from recent editions of Elektor magazine. Participation in these webinars is COMPLETELY FREE!

All you need to do is register at www.elektor.com/webinars .

Webinar programme:

Let’s Build a Chaos Generator

Date: Thursday December 1 5, 201 1
Time: 15:00 GMT (16:00 CET)

Presenters: Maarten Ambaum and R. Giles Harrison (Reading University)

Join us in this webinar to look at the making of the Chaos Generator project published
in the September and October 201 1 editions of Elektor. Get out your opamps, wipe your
monitor and glasses and turn up the volume loud!

Here comes The Elektor Bus!

Date: Thursday January 19, 2012
Time: 15:00 GMT (16:00 CET)

Presenter: Jens Nickel (Elektor)

Many Elektor readers have actively participated in designing what’s now known as the
Elektor Bus. Elektor editor Jens not only tells the story of how it all came about, but also
delve into protocols, bus confl icts and hardware considerations.

Now available to view on demand at www.element14.com

E-Blocks, Twitter and the Sailing Club

Presenters: Ben Rowland and John Dobson (Matrix Multimedia)

E-blocks are small circuit boards containing a block of electronics that you would typically
find in an electronic or embedded system. In this webinar Ben and John demonstrate rapid
prototyping of an E-Blocks configuration capable of automatically sending Twitter messa-
ges to members of a sailing club.

Platino - an ultra-versatile platform for AVR microcontroller circuits

Presenter: Clemens Valens (Elektor)

Many microcontroller applications share a common architecture: an LCD, a few pushbut-
tons and some interface circuitry to talk to the real world. Platino offers a fl exible through
hole design for such systems based on the popular AVR microcontrollers from Atmel.
Platino supports all 28 and 40 pin AVR devices, several types of LCD and has a fl exible
pushbutton and/or rotary encoder confi guration.

e I e k

FoT'‘

ACADEMY

the school of electronics

elementiu

www. element 1 4. com

Places are

MICROCONTROLLERS

Here comes the Bus! (1 0)

Readings with 22

By Jens Nickel (Elektor Germany Editorial)

This month we up the resolution: an
external ADC attached to a node delivers
samples with 22 bits of precision. Getting
the samples into the microcontroller is
easy using its SPI port. Also, we show
how to display the results on a PC with a
judiciously-modified version of the HTML
page from the previous instalment in this
series.

bits of precision

One of the pleasing things about electron-
ics is the way you can get inspiration from
other projects. In this case it was the reader
project ‘Temperature Gradient Meter’ from
last month’s issue [1]. Author Dr Diet-
mar Schroder selected an external type

MCP3551 ADC from Microchip for use in
his circuit in order to obtain the high pre-
cision required to detect minute tempera-
ture changes. This device converts voltages
to digital values with 22 bits of precision.
Figure 1 shows the tiny circuit built around

+5V

Figure 2. Printed circuit board designed
by Dietmar Schroder. XI 00 and XI 01 are
connected to l<4 on the experimental node.

f < ■-pptr.il

p ' r ? 1*. . vac C Hn«T l. lnr l T n 1 LUC I E \E

: Cwrf ■ r " lW 1 Fau’ p Ml 11 II %

Figure 1 . Circuit diagram of the high-resolution temperature sensor, with connection to

our experimental node.

Figure 3. Display of ADC values and
temperature readings in the ElektorBus

browser.

Elektor Products & Services

• Experimental nodes: printed circuit board 110258-1 or set of three • Free software download

boards 110258-1C3 (microcontroller firmware plus PC software)

• USB-to-RS485 converter (ready built and tested): 110258-91 Products and downloads available via www.elektor.com/ 1 1 061 0

38

Personal Download for I © Elektor

12-2011 elektor

this delta-sigma converter, an NTC thermistor and a couple of sup-
port components. Figure 2 shows the corresponding printed circuit
board designed by the author, which can be downloaded at [1 ]. The
ADC makes a new conversion result available at its output (an SPI
port) approximately fourteen times a second. The circuit is tailor-
made for connection to one of our experimental bus nodes. Two
pins of our eight-way connector [2] serve for the digital interface,
and two more provide power to the sensor circuit. And because the
temperature gradient meter also uses an ATmega microcontroller
to process the results, we also have a solid foundation on which to
build our code (again, see [1 ] for download).

Bit banging

The SPI port is driven using ‘bit banging’, that is, by controlling the
interface signals directly rather than using the microcontroller’s
built-in interface. I swiftly converted the C functions responsible
for this into BASCOM (see Listing 1 ). Function Readext er nal a d c ( )
waits for the ADC to pull its SDO pin low. The microcontroller then
takes the SCL signal alternately high and low: after each rising edge
one bit of the conversion result is made available by the ADC on its
SDO pin, with the most-significant bits coming first. The long vari-
able Da t stores the result as it is built up: the variable is shifted left
and if SDO is high a ‘1 ’ bit is added in. The datasheet [3] explains
that 24 bits must be read in and that an extra clock pulse should be
emitted for safety. Note that in this circuit we operate the ADC in
‘continuous conversion mode’. All that remains to be done is apply
a voltage to the ADC’s input and look at the results.

As the original article noted, because of inevitable noise in the cir-
cuit only about 1 9 bits of each conversion result are significant,
which corresponds to a still rather impressive temperature resolu-
tion of around three ten-thousandths of a degree. There is there-
fore no reason not to drop the bottom two bits of each result using
a right-shift operation. Twenty bits remain, of which the most sig-
nificant will always be zero for temperatures above — 35°C. That fits
perfectly with our ‘Application Protocol’ which allows nineteen-bit
integers (plus sign bit) to be transmitted [4]. The BASCOM code,
available for download at [5], shows clearly how the nineteen bits
are divided among the three data bytes.

Doing the initial tests was easy enough, as using the author’s board
design saved a lot of time. All I had to do was add a user interface
on the PC. I implemented this using the ideas presented in the
previous instalment in this series, based on HTML pages and the
dedicated ‘ElektorBus browser’. The HTML page ‘lndex.htm’ from
the last instalment was modified to receive a ‘VALUE4’ instead of a
‘VALUE2’ and display the received value in the text box.

User interface

With the addition of the sensor board we have turned a bus node
into a high-resolution sensor device: even just bringing your hand
near the unit produces a marked change in the temperature read-
ings. Naturally, we would like to display the readings in Celsius, and
so I have implemented the required conversion routine in the sen-
sor node firmware, using the NTC characteristic curve values (in

Listing 1 : BASCOM code to read a value from the ADC

F u n c t

i on

Rea

dex

t e r n a 1 a d c

0

Da

t =

0

Sc

k =

1

No

t i me 0 u t

—

100

Wh

i 1 e

Sdo

—

1 And Not

i me

No

t i me

out

= Not i me

out

Wa

i t ms

1

We

nd

Fo

r 1

a =

0 T

0 23

Sc

k =

0

Wa

i t u s

80

Sh

i ft

Dat

, Left ,

1

Sc

k =

1

1 f

Sdo

—

1 Then

Dat

—

Dat + 1

En

d 1 f

Wa

i t u s

80

Ne

xt

Sc

k =

0

Wa

i t u

s 80

Sc

k =

1

Wa

i t u

s 80

1 f

No

t i me

out

= 0 Then

Re

adex

t er

n a 1 a d c =

0

El

s e

Re

adex

t er

n a 1 a d c =

Dat

En

d 1

f

End F

u n c

t i 0 n

Long

> 0

1

steps of five degrees) from the temperature gradient meter code
with suitable modifications. This demonstration firmware com-
pletely avoids the use of floating-point and of division operations.
The result can be expressed in units of one ten-thousandth or one
thousandth of a degree and transmitted as a four-byte integer. Note
that the absolute accuracy of the temperature readings is not espe-
cially high unless the sensor is suitably calibrated.

The HTML user interface (Figure 3) allows switching between raw
ADC values and readings expressed in thousandths or ten-thou-
sandths of a degree. This gives a good demonstration of how a
sensor’s physical quantity, units and scaling settings can be modi-

elektor 12-2011

Personal Download for I © Elektor

39

MICROCONTROLLERS

| Listing 2: Script within the HTML page j

| var Set FI ag = f al se; j

var Quant i t yToSet = 0;

! var Seal eToSet = 0; !

var Di spl ayScal e = 0;

function ProcessPart(part)

{

if (( par t . Sender == 2) && ( pa r t . P a r 1 1 y p e == PARTTYPE_ VALUE4) )

{

if ( par t . Channel == 0) {Text boxSet val ueScal ed( ' ADC' , part. Numval ue, Di spl ayScal e) ; };

}

if ( Set FI ag==t r ue)

{

if (( par t . Sender == 2) && ( pa r t . P a r 1 1 y pe == PARTTYPE_SCALE) && ( p a r t . Ch a n n e I == 0))

{

if ( Quant i t yToSet ==TEMPERATURE) {Text Set v a I u e ( ' u n i t ' , ' 0 C' ) ; } ;
if ( Quant i t yToSet = = RA WV A L U E ) {TextSetval ue( ' uni t' , ' ADC-Val ue' ) ; };

Di spl ayScal e = Seal eToSet ;

Set FI ag = false;

}

else

{

var parts = I ni t Par t s( ) ;

parts = Set Seal e( par t s, 10, 2, 0, 0, Quant i t yToSet , 0, Seal eToSet ) ;

SendPar t s ( parts, true);

}

}

function SetSensorScal el ndi rect(quanti ty, scale)

{

Set FI ag = true;

Quant i t yToSet = quantity;

Seal eToSet = scale;

fied. The command bytes to set a sensor
to report values in ten-thousandths of a
degree using channel O are (in decimal) 40,
193, 33 and -4.

The JSBus Javascript library lets us avoid the
need to calculate these bytes by hand. The
commands shown below can be included
within the HTML page, and they will gener-
ate the appropriate ‘part’ and send it.

var parts = I ni t Par t s( ) ;
parts = Set Seal e( par t s, 10, 2,

0, 0, TEMPERATURE, 0, -4);
SendPar t s ( parts, true);

Reliable transmission

I arranged for the above lines of code to be
called when the corresponding button on
the HTML form is clicked on, exactly as in
the previous instalment of this series [6].

However, I discovered in testing that clicks
did not always have the desired effect. Now
the ‘OutCommand’ text box in the Elektor-
Bus browser showed that the message data
bytes were being generated correctly, and
so it was probably a problem with the node
firmware. My hunch was that that the mes-
sage was not being correctly received by the
sensor in the case where it was busy deal-
ing with the external ADC. I noticed that

40

Personal Download for I © Elektor

12-2011 elektor

MICROCONTROLLERS

the transfer of commands was reliable if the
variable i n t F r e e B u s T i me in the ElektorBus
browser was reduced: strictly speaking in
this application we do not need any ‘Free-
BusPhase’ at all, although we might imple-
ment the ability to control this from within
Javascript code at a later date. Unfortu-
nately, in the absence of a bus monitor or
firmware debugging facilities I was unable
to track down the source of this bug. How-
ever, it does give us an opportunity to see
how this kind of problem can be worked
around.

Listing 2 shows a solution. The buttons
for changing the unit setting call a Javas-
cript routine called SetSensorScal el ndi -
r e c t ( ) , which simply sets a flag rather than
directly sending the required command.
The master repeatedly sends this command
as long as the flag is set. The code to imple-
ment this can be integrated into the routine
ProcessPart ( part) , which is periodically
called by theJSBus library whenever a read-
ing arrives.

The flag is cleared when an acknowledge-
ment is received from the node. (The
BASCOM firmware packs the four bytes
required along with the reading in the reg-
ularly-transmitted message.) Only then is
the display of the selected unit updated
on the HTML page. To display the decimal
point properly in values shown in the text
box we call the function TextboxSetval -
u e S c a I e d ( ) , which is implemented in the
new version of JSBus [5]. The download-
able HTML file also now includes a little
CSS [7] to make the user interface some-
what prettier.

A touch of ‘optimisation’

Further testing showed that after a few min-
utes the display would lockup. Firing up the
oscilloscope it transpired that bits were still
zipping about on the bus, at least until I
stopped the scheduler. Next I arranged to
display all the bus bytes in a separate text
box, which showed that the only messages
being sent were ‘FreeBusMessages’ from
the scheduler. It was not easy to track down
the reason for this, as the scheduler is based
on three processes running in parallel. The
first is the scheduler loop itself, which inter-

rogates the nodes one after another. The
second is the routine S h o wMe s s a g e , which
is executed in parallel when a sixteen-byte
message arrives: if this message comes
from the interrogated node then the next
node in sequence can be processed. And the
third adds a timer to the mix: if a bus partici-
pant is not heard from for a certain period,
the next node is processed anyway.

I finally realised that I had made a schoolboy
error. To indicate which node comes next in
sequence I had allowed all routines direct
access to the global variable i ntPol I e d No-
de s C u r s o r , which points to the next node
in the scheduling list. If, however, this vari-
able is changed externally while the sched-
uler loop is at work, the above subtle prob-
lem can be triggered. I modified the code so
that instead a flag bool Next Node was used
to indicate when the scheduler should move
on to the next node. The flag is inspected
only at the start of the scheduler loop and
otherwise does not affect the flow of the
code. Success! The system was running
reliably, and fortunately there was time to
upload the corrected files to our website to
accompany the previous instalment of this
series. The improved ElektorBus browser
can also be downloaded at [5], in the form
ofVB.NET source code and as a .EXE file.

Some more ideas

I would have liked to implement further
features, such as a display of temperature
gradient including a filter with adjusta-
ble parameters. That would have made a
complete replacement for the processor
board, display and potentiometers of Diet-
mar Schroder’s original project. However,
time caught up with me, and time will be
even more limited in future after a slight
problem with my USB-to-RS485 converter
(see elsewhere in this edition). Interested
readers should be able to implement vari-
ous extensions to this project without too
much difficulty, given a little expertise in C
programming, the source code of the tem-
perature gradient meter, and the Bus tools
we have previously described.

Incidentally, the ElektorBus is also capable
of receiving messages from nodes. In prin-
ciple it would only be possible to have two

Setting the interval
between readings

In principle a single sensor could be re-
motely controlled over the ElektorBus
without using the scheduler. We simply
tell the device how often to report a new
reading, just as we would in a data log-
ger application.

BIT

7

6

5

4

3

2

1

0

0

0

SET

1

0

1

C2 Cl CO
CHANNEL

1

1

1

0

0

0

0

0

0

INTERVAL VALUE

0

INTERVAL SCALE

1

BYTE

Address

Command

First

Second

110610 - 13

The figure shows the four-byte applica-
tion protocol command. The interval
value is encoded in seven bits. The cod-
ing is as follows.

Hex

Dec

Interval

04

4

1 ps

05

5

10 ps

06

6

100 ps

07

7

1 ms

08

8

10 ms

09

9

100 ms

0A

10

1 s

0B

11

10s

OC

12

100s

10

16

1 minute

11

17

10 minutes

12

18

100 minutes

18

24

1 hour

19

25

10 hours

20

32

1 day

21

33

1 0 days

22

34

1 00 days

28

40

1 month

30

48

1 year

31

49

10 years

elektor 12-2011

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41

MICROCONTROLLERS

Checksums and reliabilit

When designing a bus system it is almost impossible to pay too
much attention to the problem of how to ensure messages are reli-
ably transmitted under all conditions. In the previous instalment
in this series we described two acknowledge mechanisms: one at
the message level, chiefly designed to detect collisions occurring
during the uncontrolled ‘free bus phase’; and one at the level of the
application protocol, designed to cope with interference and other
types of problem. The latter mechanism is even used when colli-
sions cannot occur, as described in the main text. In both cases the
receiver sends the received bytes back to the sender, with a simple
flag bit discriminating between the acknowledge message and the
original message. This approach seemed pretty safe to me, and so I
postponed the implementation of a message CRC or checksum.

Fortunately in the meantime many others have started to think
about how to make use of the bus. Elektor reader Werner Koch came
to the conclusion that the acknowledge mechanism was inadequate.
The mechanism does allow for a message that is lost to be resent by
the sender; but it can also happen that interference causes a receiver
to see a phantom message which has not actually been sent. As a re-
sult an actuator would generate an acknowledgement of this phan-
tom message, from which the master can deduce that something
has gone awry. However, the bad news is that the actuator might
already have changed the state of a relay, with potentially unfortu-
nate consequences.

One solution to this problem is to have the actuator wait for a con-
firmation of the command before switching the relay (a three-way
handshake). An alternative is to add redundant information to each
message: only when the checksum bits are correct will an actua-
tor switch the relay. Using this approach it is much less likely that
random interference will generate a valid message than if there had
been no checksum.

Next we have the question of whether to use a 1 6 bit CRC or a sim-
pler sum. My suggestion of banning the value AA hex from appearing
in the last two bytes, which are allocated for the checksum, met with
vehement opposition from some participants on the mailing list,

although the advantage it brings of allowing simpler synchronisa-
tion in unarguable. The alternative proposal was for a 1 6 bit CRC and
a more sophisticated approach to synchronisation. For example, the
CRC itself can be used to determine when a message is complete.

Finally I made the compromise suggestion of allowing both possibili-
ties. The distinction is indicated by a bit in the mode byte, whose
layout is now as follows.

Bit

1

0

7

no ID bytes,
payload from byte 2

ID bytes from byte 2

6

bytes 2 and 3 are ID bytes

bytes 2 to 5 are ID bytes

5

no CRC/checksum

bytes E and F form
a 1 6 bit CRC/checksum

4

advanced synchronisation

AA hex does not appear
from byte 2 onwards

3

last ID byte is fragment
number

all ID bytes used
for addressing

2

top six bits give bus
segment

no segment address

1

acknowledge message

original message

0

acknowledge message
expected

not expected

At least one of the checking functions will need to be implemented
in the AVR microcontroller C library that is currently in development.

A little later I had the idea of adding redundancy within the data pay-
load bytes, for example, an important two- or four-byte command
could be repeated within a single message, respectively four times
or twice. With non-periodic interference the probability of a valid
message of this type arising is vanishingly small.

nodes talking to one another under such a
scheme, but RS485 in combination with our
protocols nevertheless form a good basis for
the remote control of sensor equipment.
With the sensor no longer being regularly
interrogated by the scheduler it needs to
be possible to instruct it to emit readings at
specified intervals. The text box shows how
such an ‘interval command’ can be encoded
using the application protocol.

There is plenty more in the pipeline: in the

next instalment we will look at the prom-
ised connection to an Android smartphone.

(110610)

What do you think?

Feel free to write to us with your
opinions, ideas and applications.

[1] www.elektor.com/ 1 101 51

[2] www.elektor.com/ 1 10258

[3] http://ww1 .microchip.com/downloads/
en/DeviceDoc/21 950e.pdf

[4] www.elektor.com/ 1 10428

[5] www.elektor. com/1 10610

[6] www.elektor. com/1 10517

[7] http://en.wikipedia.org/wiki/
Cascading_Style_Sheets

42

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Work in progress

The Elektor Labs generally remain a closed fortress, with access to Elektor House limited to those who happen visit the castle
during one of the annual Dutch Open Monument Days. Whatever happens in the lab usually remains behind closed doors. That,
of course, does not mean that there is nothing interesting going on. So here’s a first, small ‘peep show’ of two projects that are
being worked on in the lab at the moment. First the new LCR Meter. Designer Raymond Vermeulen and colleague Jan Visser are

The second photo series shows the efforts of Head of Design Chris Vossen working on his version of a 3D printer. The publication
date remains a secret for now, but for more information about this exciting project and the latest state of affairs you can take a
look at www.techthefuture.com/3D-printer.

elektor 12-2011

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43

E-LABs INSIDE

E-LABs INSIDE

LED Exorcism

Ghostly
goings-on (2)

By Dr. Thomas Scherer (Germany)
& Elektor readers

In the September 2011 issue I
recounted how I had witnessed the
demise of two different LEDs both
of which inexplicably began to flash
on and off before they died. In the
absence of any reasonable explana-
tion we blamed it on an LED spirit.

The ink was hardly dry on the Sep-
tember edition before your replies
started coming in, some interest-
ing, some informed, some tongue
in cheek and some, well, bizarre.

Just to recap before we start with your replies: a standard low the LED is cool, but loses contact when the LED heats up, then the

power LED used in a recharging circuit of an electric corkscrew LED will blink until the break becomes permanent See: http://www.

and a high powered display LED both showed the same behav- emsnow.com/cnt/files/White Papers/DFRLEDFailures.pdf. ,,
iour when they were about to give up the ghost; they started Craig was not the only one to point the finger of suspicion at the

flashing. In both cases the circuitry around the LED couldn’t wire bond contact point on the LED chip as the cause of the inter-

be much simpler, a series resistor to limit current and an AC mittent behaviour. One reader even went on to suggest a fix...
power adapter to supply, ermm, current. It’s no wonder engi-
neers were rubbing their eyes in disbelief. We couldn’t explain Karl-Heinz Ziener from Germany:

the phenomenon; the editors agreed we should draw on the “I would guess that a hairline crack has developed in the bonding

combined wisdom of our readership to help lay the ghost: wire to the LED chip. When power is first connected the LED is cold

and the two parts either side of the crack are touching, current
Wolfgang Bredow from Lilienthal, Germany wrote: flows and the LED lights up. The LED warms up, expands and breaks

“ When I read your article in the September edition it immediately the contact. Now with no current flowing the LED cools down, con-

put me in mind of an experiment I carried out in the late 7 970s. At tracts and makes contact again, so the cycle repeats,

that time I was using a curve tracer to record the operating charac- A ( not entirely sincere) repair bodge suggestion is shown in Fig-

teristics of electrical components. On a whim I decided to over-drive ure 2: Connect a capacitor in parallel across the LED. When the

an LED to record its characteristics as it failed. The resulting curve LED goes out the capacitor will charge to full battery voltage. As the

can be seen in Figure 1. LED cools down contact is made again and the capacitor releases

The curve shows the victim (a green LED) being driven way beyond its stored charge through the LED, permanently welding the two

is recommended safe operating area. With the supply approaching parts either side of the crack together, job done! “

7 V the LED was drawing around 500 mA when the emitted light
changed to dark red. Next it began to flash (aha!!!), the electrome-
chanical curve tracer now started to go a little crazy trying to keep
up with the step changes in the LED's characteristics. The dashed
line indicates where it failed in this task! ”

Mr Bredow assured us that this was the only time ever he had
been guilty of deliberately causing the demise of an innocent
component...

Craig Hyatt writes from a .com email address:

“ The answer Is pretty simple. The LED is made of a variety of
materials with different expansion coefficients. When the LED cycles
on and off, the materials expand and contract at different rates,
and this causes mechanical stress that can cause a bond wire to Figure 2. Heal Thyself: Charge stored in the capacitor should be

separate from the substrate. If the bond wire makes contact when sufficient to weld the wire bond back on the chip.

TU

L *

4

Figure 1. Original curve trace of a failing LED from the 1970s.

44

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12-2011 elektor

For this to have any chance of working the LED must still be
partly working i.e. flashing but not completely dead. ;-)

Gwyn Evans in Munich got in touch via his smartphone:
Obviously the reason for your observations is that the 9 VDC isn’t
quite DC, it's half rectified AC and what you are observing is a
localized breakdown in the space-time continuum, resulting in a
50 times or so reduction in perceive time. This is nothing to worry
about, and due to the induced effect resulting from Lorentz Con-
traction your flat will appear bigger too.

Alternatively the result is probably due to a heating effect. As an
LED ages it can become more sensitive to ambient temperature. The
LEDs temperature rises causing the LED to fail. The LED then cools
allowing it to recover and start working again.

Right, OK, glad we got that one sorted out then... Gwyn went on:
“It is possible to extend the life of an LED by pulsing it; usually 1 kHz
is sufficients

I’m wondering now if I should suggest to the utility companies
that they derive the powerline frequency directly from the out-
put of wind turbines...

Hubert Maiwald from Neutraubling, Germany:

“ The majority of LEDs consist of a single die cemented to the lead frame
with silver-loaded conductive adhesive forming one electrical connec-
tion and a wire bond forming the other contact on top of the die.

This adhesive is the weak point; it can be damaged by excessive solder
temperature during installation or dissipation of too much power in

operation. At high temperature the adhesive starts to give offgas,
generating voids in the interface between the die and lead frame.
This damage degrades the thermal path and reduces the LED’s
power handling abilities further, leading to more localised adhesive
gassing and more voids. As die temperature increases the emitted
light wavelength shifts, becoming longer.

Eventually there is very little contact area remaining and the LED
mould material becomes locally heated so that expansion of the
materials exerts pressure on the die and interrupts the current flow.
With no current flowing the die temperature falls and contraction
pulls it back to its original position, re-establishing contact. The die
now heats up again and the process repeats...

The thermal time constant of this oscillation is in the range 0. 1 to
1 0 s, depending on current and power dissipated. This flashing mech-
anism is effectively the same as the old mechanical bi-metal relays.
Incidentally of all the ways an LED can be destroyed this mechanism
is not particularly probable. For it to occur it must be assumed that
the diode junction is not damaged and also that the bond wire is still
intact. More often than not the die bond adhesive just becomes irre-
versibly damaged and the LED simply goes open-circuit. “

Seems logical?

So, dear reader, did any of that sound like a plausible explana-
tion? The consensus suggests a link to thermal effects but that
is the fascination with electronics there are always puzzles to
solve, sometimes in the most unexpected places.

(110668)

Pins to length

By Thijs Beckers (Elektor Netherlands Editor)

In a previous E-LABs Inside instalment we already mentioned
placing a piece of experimenter’s board between an LCD and
a (mother)board, with the objective of making the display eas-
ier to remove and without damaging it. This was targeted spe-
cifically at the more fragile displays, such as the DOGM-series
made by Electronic Assemblies. Now there is even a second trick
for this experimenter’s board.

The DOGM displays mentioned above ‘stand quite tall on their
legs’ (have quite long connecting pins). This length is neces-
sary when they will be provided with a backlight that — and the
name gives it away already — is fitted behind the display. But
when this backlight is omitted, it is often much better that the

display is mounted closer to the PCB, so that, for example, the
entire assembly is more compact when building into an enclo-
sure. When there are sockets on the PCB for connecting the dis-
play, then the only option for fitting the display closer to the PCB
is to shorten all the pins. It is then desirable that all the pins have
the same length. And here is where our experimenter’s board
comes in handy again: insert the pins of the display as far as they
go into the board and cut off the part that sticks through. The
length of the pin that remains is then perfect for plugging into
a header. And all the pins have exactly the same length, so that
the display cannot not rock in its socket.

Do you have any handy tips for us?

Mail them to editor@elektor.com.

(110664)

elektor 12-2011

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45

E-LABs INSIDE

After weeks of devotion to a project it has finally reached that
stage: you order the circuit board, the components and when
everything has arrived you start the assembly. Then it turns out
that the footprint for one of your ICs is not right. What now?

In my case the culprit was a DS2003 relay driver. Since 2009 the
version in the TSSOP-package is (apparently...) no longer made.
Only the SOIC version still runs off the production line. It is nice
that we now know that, but too late!

Instead of ordering a new circuit board with the footprint cor-
rected, which takes another few weeks (faster is possible, but
gets a bit expensive) and wasting the time and effort that you
have invested in that part of the board you have built already,
it is time to improvise.

The solution in this case (see photo) is ‘quick’ but ‘very dirty’.
Fortunately this 1C is only used to switch a few relays. In appli-
cations where the signal quality is important, this method is
not so suitable.

What I have done: First I soldered a piece of very thin enam-
elled wire to each of the little legs. Then I cut all the wires to the
same length and bent the ends over. The reason that the wires
are this long, is not only so that you can get a soldering iron in

between, but also because otherwise the other end of the wire
is likely to unsolder because of heat conduction when you are
soldering this end.

If you have a steady hand then the soldering is not that diffi-
cult. For people with a slightly less steady hand, such as me,
this becomes rather tricky, but I was still successful in the end.
It’s a good idea to fix the 1C in place first and to strip the wires
of enamel where they will be soldered. But the best solution
of all is just to use the correct footprint on your circuit board...

(110692-I)

ItsyBitsy Spider...

By Raymond Vermeulen (Elektor Labs)

Smelly bus

By Thijs Beckers
(Elektor Netherlands Editor)

While quietly working on the article
about the use of cheap tablets in embed-
ded electronics (see elsewhere in this
edition) I suddenly noticed that typical
smell of burnt electronics. Following my
nose (and as a member of the First Aid
team I’m of course more or less obliged to act on the smell of
fire), I arrived in the adjoining room with the German editorial
staff, where colleague jens Nickel was working on the Elektor
Bus project. Was, because it appeared that the tantalum elec-
trolytic capacitor on the USB/RS485 converter, which is part of
the Elektor Bus system [1 ], had given up (see photo). Jens was
already back in the lab with the faulty board, but an odour like
that of burnt bakelite was still in the air.

We were of course not at all happy with this. What if this could
happen to all the boards that have already been sold? Was this
a manufacturing fault or are the tantalum capacitors mounted
the wrong way around? Do we have to recall all those boards
out there? Is this our fault or that of the assembler? Who will go
ballistic? Who will foot the bill?

Checking the stock that was still in the warehouse should give
a definitive answer. It was already towards the end of the after-
noon, so this would have to wait till tomorrow, because our ware-
house is in an industrial area about 6 miles from Elektor House.

v

* /
/

'1*.

In short, the next day we immedi-
ately checked whether the remaining
stock (and therefore also the boards
already supplied) were built correctly
or whether we had a big problem.

What emerged: We could breathe a sigh of relief, because the
boards we pulled out of stock were built correctly. What we
noticed though, is that different components were used on
the boards we have in stock. And then it dawned on us... The
modules that Jens was using were early prototypes built in the
lab, hence the different components compared to the produc-
tion version. Probably whoever assembled them didn’t realise
that with tantalum capacitors the + is marked (with electrolytic
capacitors the - is usually marked).

So this fortunately ended in a fizzle (well, more like smoker).
So here you have one example of all the kinds of things you
can come across during the development of a project. It is cer-
tainly not likely to be boring! What surprised us quite a bit how-
ever, is how long this tantalum capacitor was able to hang on
while being reverse polarised. There was nothing unusual to be
noticed about the functionality of the circuit.

(110693-I)

46

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HOME & GARDEN

Pick-proof Code Lock

Using 128-bit AES encryption

By Elbert Jan van Veldhuizen (The Netherlands)

How secure is the remote control of your car or other valuable vehicle? This project shows you
how to use a couple of ordinary microcontrollers together with a transmitter and a receiver
to implement an IR remote control system that uses a secure code with 128-bit AES encryption and
bidirectional IR data communication.

We’re all familiar with remotely controlled
door lock systems in cars. The remote con-
trol transmits a code, and if the receiver of
the lock system recognises the right code, it
unlocks the doors. A drawback of systems of
this sort is that people with malicious inten-
tions who eavesdrop on the code transmis-
sion can effectively pick the lock, since they
can transmit the code at any desired time to
unlock the car.

A much more secure method is the chal-
lenge-response handshake authentication
protocol, which is used for many forms
of Internet banking. With this approach
the lock transmits a specific code and the
remote control must perform a defined
computation using this code. The result is
then send back to the lock. The lock remains
locked unless the right computation has
been performed.

Eavesdropping on the communication
between the lock and the remote control is
useless in this situation, because the next
time the lock will send a different code for
the computation. As long as anyone with
malicious intentions does not know the
computation, the lock cannot be picked.
Here it’s important to choose a good com-
putation method. Encryption is very suit-
able for this. Encryption uses a key to con-
vert data into new data, which is exactly the
type of computation that we need for the
remote control system.

Encryption algorithm

What makes an encryption algorithm good?
Encryption is a process in which data to be
encrypted (in) is converted into encrypted
data (out) with the aid of a key, which is
something like a password.

• The encryption algorithm implements
the function out = f (in, key). The inverse
function in = f tnv (out, key) also exists, but
the function key = f key (/n, out) does not
exist.

• For each value of in there is a unique
value of out. In other words, there are
not multiple values of in that generate
the same value of out.

• This also applies to the key: two different
keys produce two unique encrypted out
values.

The first condition ensures that if persons

with malicious intentions learn the values

of both in and out by eavesdropping, they
will not be able to derive the key by using
a function f key . The only way to determine
the key is to use what is called a brute force
attack, which consists of trying all possi-
ble keys in the encryption function f. This
requires spending so much time search-
ing for the key that trying all possible val-
ues takes too long. Powerful computers
can try all possible values of a 64-bit key in
approximately one day. With a 1 28-bit key,
this would take more the lifetime of the uni-
verse, which is long enough to be secure.
We chose the AES protocol for the encryp-
tion algorithm. This encryption algorithm

:(

IC2

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18_

1_

2 _

4

9_

10

11

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14

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RA1

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RA3 RB2

RA5

RA4

RBO

RB3 RA6

RB4

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RB5 RB6

18-Pin PDIP
RBI RB7

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16

15

12

13

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330R

330R

w

330R

o o

J1

o o

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IR

<s>

110358 - 11

Figure 1 . Schematic diagram of the base station.

48

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12-2011 elektor

HOME & GARDEN

u

is used in devices such as WiFi routers to
prevent eavesdropping on data traffic and
breaking into the network. This algorithm
has not been cracked up to now. In other
words, nobody has found a function f key or
some other way to determine the right key
with fewer attempts.

The AES algorithm needs a lot of resources
compared to what is customary in the
microcontroller realm. Over 240 bytes of
RAM are necessary for the computations,
the code consists of approximately 1 500
instructions, and execution of the compu-
tation takes approximately 30,000 instruc-
tion cycles. Furthermore, tables and arrays

are used extensively.

The new PIC1 6F1 827 enhanced microcon-
troller from Microchip is a device that ful-
fils these requirements. It has 4096 words
of code memory and 396 bytes of RAM. It
can also run at up to 32 MHz using its inter-
nal clock, and the microcontroller has a
new instruction set called “enhanced mid
range” that makes working with arrays a
good deal easier. Although the RAM is split
into individual blocks of 80 bytes each, the
enhanced instruction set allows these indi-
vidual blocks to be viewed as a single large
block (linear mode), which facilitates access
to tables.

The circuit

Aside from the microcontrollers, only a few
components are needed to implement prac-
tical circuits (transmitter and receiver) that
utilise this encryption method. Figure 1
shows the circuit diagram of the base sta-
tion (the lock), while Figure 2 shows the
circuit diagram of the remote control. They
communicate using infrared LEDs, in the
same was as remote controls for television
sets. LED D1 is used for transmission, while
IC2 (a standard IR module from Sharp with
an operating frequency of 36 kHZ) is used
for reception. The switches for operating
the devices and configuring the parameters
are connected directly to the I/O ports. The
‘weak pull-up’ capability of the microcon-
troller make resistors unnecessary here. A
keypad for entering a PIN code can also be
connected to the remote control. A matrix
keypad should be used for this purpose.
The remote control operates directly from
two AAA batteries, but a lithium button cell
can also be used. The base station can be
powered from a mains adapter. The usable
supply voltage range is 1 .8 to 5 V. Note that
the maximum rated voltage of the LF ver-
sion of the microcontroller is 3.3 V.

Operation

A communication session starts when the
remote control sends the code ‘A6h’. The
base station then generates a random 1 28-
bit number. A random number is better
than a predictable number because the lock
can potentially be picked by ‘code phishing’
if a predictable number is used. The encryp-
tion algorithm is also an excellent random
number generator (see inset), using an
input value derived from a counter. The
encryption algorithm converts the input
value into a random number (using a sepa-

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11

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110358 - 12

Figure 2. Schematic diagram of the remote control.

elektor 12-2011

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Usinq encryption for random number qeneration

Linear feedback shift registers are commonly used to generate random numbers. Their
output bit streams have the statistical characteristics of randomness, but the bit streams
are predictable. As the algorithm is known, the state of the shift register can be reproduced
after a specific data set has been read in. This allows the values to be predicted.

A good encryption algorithm also has the statistical characteristics of randomness. Due to
the unique mapping from input to output, the ratio of ones and zeros will be exactly 50%.
However, the bit stream is totally unpredictable because the key is not known. The pat-
tern repeats itself (or the key can be determined by calculation) only after the entire bit
stream has been generated (in this case 2 131 bits). If this bit stream is transmitted at a rate
of 1 Gbit/s, it will take a trillion times as long as the lifetime of the universe to transmit the
entire bit stream.

0,5 ms 0,5 ms 0,5 ms

Figure 3. A variant of the Sharp protocol is used to transmit data using IR pulses.

rate key). The countervalue is saved in flash
memory so that unique numbers can still
be generated after a power interruption.
As the flash memory has a maximum rated
life of 1 00,000 write operations, the value
is saved to memory only once every 65,536
times, and a different memory location is
used each time. In the unlikely event that
the maximum number of write operations
is reached (after 13 million power inter-
ruptions or 900 million transactions), an
emergency procedure is invoked to ensure
that the user is not left standing in front of
a locked door. This procedure requires the
user to press the remote control button 1 6
times in a row. After this the random num-
ber is derived from the timing of the code
transmission by the remote control.

IR communication

The remote control first reads the 128-bit
number. Standard modules can only han-
dle a maximum duty cycle of 30% with
such long transmissions. The commonly
used Manchester coding method (used in
the RC5 protocol, for example) has a duty
cycle of 50%. For this reason, a variant of
the Sharp protocol is used here. The ‘1’
and ‘0’ values are defined by the length of
the break between two pulses. A break of
0.67 ms is a ‘O’, while a break of 1 .33 ms is a
‘1 ’. The pulse width is 0.5 ms, and the end of

the pulse train is indicated by a break lasting
longer than 2 ms (see Figure 3). The tim-
ing tolerances are loose and the algorithm
is self-synchronising, so the accuracy of the
clock oscillator does not need to be espe-
cially high. This protocol can also be used
to transmit 8-bit words (or words of any
desired length) as easily as 1 28-bit words,
thanks to the use of a stop bit.

Both the remote control and the base sta-
tion apply encryption to the 128-bit ran-
dom number, using the same key. The
remote control sends the encrypted 128-
bit number back to the base station. The
base station compares the received num-
ber to the one it computed itself. If they
match, the base station opens the lock.
Depending on the setting of jumper 1 , the
base station may return a code indicating a
match (OxAB) or no match (0xB5). In theory,
returning a result code makes it possible to
pick the lock using an automated method,
although this is rather unlikely in practice.
Nevertheless, if you consider the risk too
great you can fit jumper 1 to prevent trans-
mission of result codes.

Jumper 1 on the remote control board has
a similar function: the remote control emits
a low beep tone if the code is wrong or the
base station does not send a response. Fit-
ting the jumper disables this beep.

Generating the key

Jumper 2 enables key programming. This
requires switching the base station off
and on again. If you now press SI 32 times
in a row, two keys will be generated. The
red LED goes dark briefly when this has
been completed. The timing of the button
presses yields totally random numbers due
to the speed of the counter. These numbers
are stored in the EEPROM. After this the
remote control must be programmed with
the same key. For this purpose, jumper 2
on the remote control board must also be
fitted. After this the remote control sends
the code ‘OxAD’ (you may have to press the
# button or enter the PIN code first). The
base station then sends the key twice. The
remote control checks that the two trans-
mitted numbers are the same and then
saves the key in the EEPROM (the green
LED lights up and a beep sounds). This
can be repeated with each remote control
unit. Remove the jumpers and switch the
units off to restore the base station and the
remote control to normal operation.

For security reasons, the key can only be
sent to the remote control immediately
after it has been generated in the base sta-
tion. This prevents the ‘clandestine’ pro-
gramming of another remote control at a
later time. This can only be done by generat-
ing a new key, with the result that the origi-
nal remote control will no longer work, so
the action will always be detected.

In addition, data protection of the EEPROM
and the program memory is enabled in
both the base station and the remote con-
trol. This means that the key can never be
read out. Furthermore, the key is not known
when it is generated because the user sim-
ply presses the button, without knowing
the value of the key that is generated in this
manner. The key is thus stored securely in
the microcontroller.

However, there is a risk: when the base sta-
tion and the remote control are both brand
new (not yet programmed), the system is
already operational because both EEPROMs
are filled with ‘OxFF’, so both microcon-
trollers have the same key. A user might
think that there is no need to program the
key, and a person with malicious inten-

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tions could use the key ‘FF...FF’ to try to
open locks of this sort. To prevent this, the
remote control unit (but not the base sta-
tion) always increments the key read from
the EEPROM, so that the keys are not the
same. When the key is programmed the
value is decremented, with the ultimate
result that the right key is used.

PIN code

The remote control is equipped with a key-
pad for entering a PIN code. The PIN code
is disabled by default. If you do not wish to
use a PIN code, simply connect a pushbut-
ton between RA3 and RBO (this corresponds
to the # key on the keypad). The PIN code
can be set by fitting jumper 2 and pressing
the * key (or entering the current PIN code
if it has already been set) and then entering
the new PIN code twice in a row. To disable
the PIN code, a new PIN code must be set
with a value of ####or ****.

If a PIN code has been set, it must be
entered when the remote control is acti-
vated. If the wrong PIN code is entered
three times, the remote control is blocked
by erasing the key. After this the remote
control must be resynchronised with the
base station by generating and program-
ming a new key.

On/off

You may have noticed that the remote
control does not have a power switch. The
‘problem’ here is that the power consump-
tion of the latest PIC microcontrollers is
so low that the circuit does not switch off
immediately, due to energy storage in the
decoupling capacitor. For this reason, we
chose a different solution. After five sec-
onds, the remote control enters sleep
mode, and in this mode it consumes virtu-
ally zero current (much less than the self-
discharge rate of the batteries). The # key
generates an interrupt and is therefore
effectively the ‘On’ switch.

The software

The author converted existing open source
C++ code for the AES routines (the source
is stated in the code) into assembly lan-
guage because the code was not compiled
properly by the C compilers for PIC micro-
controllers. The program code for the base

Figure 4. Both circuits can easily be built on
pieces of prototyping board.

station and the remote control is located
in a single file because many routines are
the same for both devices. The correct hex
file can be generated by placing ‘#define
remote’ or ‘#define homestation’ at the
start of the code. Naturally, the code can
also be modified.

The IR LED and the IR sensor are connected
to the serial port (TX/RX). Other devices,
such as a GSM modem, could also be con-
nected to this port. This would allow a lock
(or other device) to be actuated securely
anywhere in the world by sending text
messages.

The user interface

Using the devices is simple after the key has
been programmed as described above.

• Press the # key on the remote control to
activate it. If the LEDs blink rapidly, the
PIN code must be entered. If an incor-
rect PIN code is entered three times,
the red LED blinks constantly and the
remote control must be resynchronised.

• Three different beep/visual results are
possible at this point:

• High beep tone / green LED - low
beep tone / red LED: base station not
responding (may be too far away or not
switched on)

Figure 5. The IR LED and the IR receiver are
located next to each other, facing in the
same direction.

• High beep tone / green LED - low beep
tone / green LED: wrong key; lock
remains locked (or the remote control
may be blocked)

• High beep tone / green LED - high beep
tone / green LED - high beep tone /
green LED: lock opened

• If jumper 2 is fitted, only the sequence
'high beep tone / green LED - high beep
tone / green LED' occurs in the latter two
situations. In this case opening of the
lock (or otherwise) is the only indication
of whether the right key was used.

• The # key can be pressed again within
5 seconds to send another unlock
request without requiring new entry of
the PIN code.

• The remote control switches off auto-
matically after 5 seconds without user
activity.

(110358)

Note: If you manage to discover
a way to reveal the code of this
code lock, please let the editors
know: editor@elektor.com

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Audio DSP Course (6)

Part 6:

Digital signal generator

An audio signal generator for lab use needs to have two basic features. First, it must be able

DSP COURSE

to generate low-distortion sine waves with an adjustable frequency and amplitude to allow
measurement of the frequency response and distortion factors of audio equipment; and second, it
must be able to generate low-pass and band-pass noise signals to help characterise electro-acoustic
transducers. A DSP makes the ideal basis for such a device. The DSP board we have described in this series
of articles is used here as the central component in a lab-grade signal generator, generating high-quality
output in both digital and analogue forms.

By Alexander Potchinkov (Germany)

An audio signal generator is a fundamental
item of test equipment in any small audio
or electro-acoustics laboratory. For the
utmost in flexibility the generator should
ideally be able to produce output in ana-
logue or digital form and have two out-
put channels, allowing test signals to be
fed simultaneously to analogue and digi-
tal devices. It is useful to be able to carry
out measurements both in the lab, such as
on one’s homebrew loudspeakers, and on
devices when installed at their final place of
use, for example to measure the frequency
response of a speaker system when installed
at a large event. We also want to be able to
measure both linear and non-linear distor-
tions in equipment.

To this end the audio signal generator
described in this article provides test sig-
nals of sufficiently high quality to ensure
that such measurements can be made accu-
rately. If the top end of the frequency range
required is not unreasonably high (in most
cases for audio measurements the audi-
ble range from 20 Hz to 20 kHz is plenty)
then we can realise the generator using the
DSP. The result is an unbeatable combina-

tion of low cost and high signal quality: for
sine wave signals this means low distor-
tion and low noise, and for noise signals it
means that the characteristics of the noise
filter are tightly controlled. Analogue signal
generators (under comparable conditions)
cannot match the performance of our dig-
ital system. To turn the DSP board into a
piece of test equipment we need to add a
user interface to allow the entry of various
settings and, if wanted, an extra analogue
output stage. In this article we will describe
the signal processing and the DSP program
that implements it, closing with some notes
on how a user interface can be constructed.

Signal processing in the digital
audio generator

Figure 1 shows the block diagram of the
signal processing involved in one of the two
identical channels in the system (which we
shall call the ‘left’ and ‘right’ channels), fea-
turing two basic signal sources. One is a sine
wave generator with adjustable frequency
and the other is a white noise generator.
Following the noise generator is a bank of
42 spectrum-shaping filters with a switch to
select between them. Then there is a signal
source selection switch and an attenua-
tor. Depending on the switch settings and
the selected filter the system can produce

either a sine wave or filtered noise at its
output. The two channels are independ-
ent of one another, allowing the simultane-
ous generation of a sine wave and (filtered)
noise signals.

The signal processing chain shown in Fig-
ure 1 requires a total of five parameter val-
ues: the phase increment d4>, which sets
the frequency of the sine wave, the index
F| of the noise filter (regarding this index
as a switch setting), the position of signal
source selection switch S 1} the attenua-
tion factor a and the noise signal amplifica-
tion factor ‘Gain’, which can be set in steps
of 6 dB (that is, each step corresponding
to a doubling in output amplitude). Using
the parameters a and Gain in combination
allows any desired gain value between the
6 dB steps to be obtained. Because there are
two independent channels the DSP code will
need two separate areas each storing a set
of five parameters.

We will now describe the three main blocks
in the signal processing chain in turn: the
sine wave generator, the noise generator
and the digital noise spectrum filter.

Sine wave generator

There are two main approaches to generat-
ing a digital sine wave of the form

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x(n) =

a sin (2nnf s lf T ), n =

0 , 1 ,...

where f T is the sample rate,
f s <f T /2 is the oscillation frequency,
the phase offset is zero and a is the
amplitude. Note that the accumulator rep-
resents values from -1 to +1 rather than
from 0 to 1 , hence must work modulo 2.
The first approach is to use an oscillator
with feedback, such as the Wien bridge cir-
cuit well known in analogue electronics. In
digital form this is known as a second-order
recursive oscillator. In both analogue and
digital forms if there are stringent require-
ments on distortion then some form of
amplitude control is required.

The second approach is to use a phase accu-
mulator followed by a non-linear function
mapper, as used in the ‘DDS [Direct Digi-
tal Synthesis] RF Signal Generator’ project
published in Elektor in October 2003. In the
digital sine wave generator the phase accu-
mulator produces a sawtooth output with
a period equal to that of the desired sine
wave. The non-linear mapper modifies the
sawtooth signal into a sine wave. In ana-
logue electronics this can be achieved using
a network of diodes and with the phase
accumulator outputting a triangle wave,
but unfortunately the design requires a lot
of adjustments and is sensitive to tempera-
ture-dependencies of the components, and
does not usually give satisfactory results.
The function mapper in the digital version
usually takes the form of a ‘look-up table’
storing one cycle of a sine wave sampled at
perhaps 1 024 equally-spaced points in time.
If the output value from the phase accu-
mulator should not fall exactly on one of
the stored sine wave sample points, linear
interpolation can be used between the two
neighbouring values. One disadvantage
of this approach is that signal distortion
depends on frequency and becomes worse
if more points need to be derived using
interpolation. An alternative to linear inter-
polation is to use a polynomial approxima-
tion: one one hand this requires rather more
computing power to evaluate the approxi-
mating polynomial, but on the other hand it
is often possible to reduce the required size
of the look-up table and guarantee a lower

lllllllllllllllllll

ii

level of distortion; however, the degree of
distortion still rises with frequency.

We have chosen to use this last approach as
the spectral quality of the sine wave output
is our primary goal. In other words, going to
the effort of generating a sine wave digitally
is only worthwhile if we can achieve a lower
distortion figure than can be obtained using

2x3/48 = 0.125. The two’s complement
arithmetic used by the DSP56374 lets us
view numeric values as being arranged in
a circle and automatically produces the
desired sawtooth waveform without further
processing. The value in the phase accu-
mulator is held in double-precision format
(as a 48-bit quantity) and is moved to and

Figure 1 . Block diagram of the signal processing chain.

affordable analogue technology. Moreover,
the computation burden can easily be han-
dled by the DSP, and so we have no excuse
for using the simpler approaches. Inter-
ested readers may like to know that the
polynomial coefficients used in the code
were obtained using a Chebyshev approxi-
mation, and that we use a degree-1 1 inter-
polating polynomial evaluated using the
Horner scheme.

The phase accumulator is initialised to zero.
For each new sample its value is increased
by the phase increment d(f> = 2 f s /f T . If the
sample rate f T is 48 kHz and we want to
generate a sine wave with a frequency f s
of 3 kHz, then the increment will be d4> =

from memory using the processor’s 48-bit
move instructions. The frequency stability
of our oscillator is determined by that of the
master crystal oscillator on the DSP board
and should easily be enough for any audio
application.

Noise generator

For the noise generator there are again sev-
eral implementation options. We have gone
for the most straightforward, using a shift
register with feedback. In this case, how-
ever, ‘straightforward’ does not equate to
‘of poor quality’. The shift register approach
has been used for a long time in construct-
ing analogue noise generators with the help
of a couple of digital logic ICs. If you take a

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Table 1: Filter selection indices

Filter index

Filter

0

White noise (no spectrum shaping)

1

Pink noise filter

2

One-third-octave filter, centre frequency f m = 25 Hz

...

...

31

One-third-octave filter, centre frequency f m = 20 kHz

32

One-octave filter, centre frequency f m = 31 .5 Hz

...

...

41

One-octave filter, centre frequency f m = 1 6 kHz

Table 2: Cain points of one-third-octave

and one-octave filters with centre frequency f m = 1 kHz

One-third-octave

One octave

Gain

left

right

left

right

-3dB

895 Hz

1117 Hz

718 Hz

1393 Hz

-20 dB

790 Hz

1266 Hz

509 Hz

1958 Hz

-40 dB

611 Hz

1636 Hz

291 Hz

3385 Hz

-60 dB

385 Hz

2581 Hz

145 Hz

6507 Hz

Table 3: Program parameters and valid ranges

Parameter

Range*

Data type

Word length

Alignment

SL,

SR

[0,1]

Integer

24

right-aligned

Fi L,

Fi R

[0,1 41]

Integer

24

right-aligned

Dphi L,

Dphi R

(0,1)

Fractional

48

left-aligned

A 1 p h a L ,

Al p h a R

(0,1)

Fractional

24

left-aligned

Ga i n L ,

Gai nR

[0,1,.. .,6]

Integer

24

right-aligned

* Square brackets indicate that the range interval is ‘closed’, in other words, that the limiting values are included
in tne range. Round brackets indicate an ‘open’ interval, where the limiting values are not included.

Table 4: Default parameter values

Program parameters (left channel)

Program parameters (right channel)

Parameter name

Default value

Parameter name

Default value

Dphi L

0.041666667

Dphi R

0.041666667

Fi L

18

Fi R

18

SL

0

SR

1

Al p h a L

0.5

Al p h a R

0.5

Ga i n L

0

Gai nR

1

Table 5: Program files for the audio signal generator

Audi oGen. asm

Main program

Ko c z _ S i n Co ef . t a b

Sine wave polynomial coefficients

El ektorFi 1 ter. tab

Digital filter coefficients

s r c 4 3 9 2 . tab

Byte sequence for configuring the SRC

i v t . asm

Interrupt vector table entries for the audio interrupts

es ai 4 r 2 1 . asm

Audio interrupt service routine:

four input channels, two output channels

mi o e q u . asm

Handy names for the DSP I/O addresses

look at the DSP code, you will see that the
software realisation is very simple indeed.
The noise output is actually a periodic signal
(or ‘pseudo-noise’): in one period of the sig-
nal the shift register passes through every
allowable state. Only one state (the register
containing all zeros) is not allowable: if the
shift register does get into this state it can
never leave it.

To give a concrete example, if the shift reg-
ister consists of four flip-flops then of the
sixteen possible states 1 5 =2 4 -1 are allow-
able, corresponding to the numbers from 1
to 1 5. We use a shift register comprising 24
flip-flops, giving a total period of around six
minutes at a sample rate of 48 kHz. This is
long enough for any audio application. The
two generators have different feedback
combinations which ensures that the two
outputs are for practical purposes uncor-
related and statistically independent: this
is important when making two-channel
measurements. Again we put emphasis on
the quality of the signal processing in this
project.

Filters

The filters are used to shape the spectrum
of the noise. The indices of the digital filters
within the bank of 42 are given in Table 1
and the filters themselves are as follows.

• A dummy filter for white noise.

• A pink noise low-pass filter, which gener-
ates pink noise from white noise. Loud-
speaker experts among our readers will
know that using pink noise is important
for protecting sensitive tweeters from
overheating, and that when testing
loudspeakers using one-third-octave
analysis bands a pink noise input should
give a uniform output.

• Thirty one-third-octave band-pass filters
to generate noise within bands one third
of an octave wide with nominal centre
frequencies at 25 Hz, 31.5 Hz, 40 Hz,

50 Hz, 63 Hz, 80 Hz, 1 00 Hz, 1 25 Hz,

1 60 Hz, 200 Hz, 250 Hz, 31 5 Hz, 400 Hz,
500 Hz, 630 Hz, 800 Hz, 1 000 Hz,

1 250 Hz, 1 600 Hz, 2000 Hz, 2500 Hz,
3150 Hz, 4000 Hz, 5000 Hz, 6300 Hz,

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Figure 2. Normalised frequency responses of the one-third- Figure 3. Spectrum of the 1 kHz sine wave oscillator output,

octave and one-octave filters, in decibels.

8000 Hz, 1 0000 Hz, 1 2500 Hz, 1 6000 Hz
and 20000 Hz: these values are as speci-
fied in BS (DIN) EN 61 260.

• Ten one-octave band-pass filters to gen-
erate noise within octave-wide bands
with nominal centre frequencies at
31.5 Hz, 63 Hz, 1 25 Hz, 250 Hz, 500 Hz,

1 000 Hz, 2000 Hz, 4000 Hz, 8000 Hz
and 1 6000 Hz, again in accordance with
BS (DIN) EN 61 260.

By way of an example Figure 2 shows the
frequency response of a one-third-octave
and a one-octave filter with normalised cen-
tre frequency. Table 2 shows various points
on the response curve of the two filter types
when centred in the middle of the audible
range at 1 kHz, giving the frequencies at
which certain levels of attenuation occur.
The 3 dB points of the filter are highlighted
in the table.

Since the filters are implemented digi-
tally and we are using sample rate of only
48 kHz the centre frequencies of the filters
at higher frequencies tend to deviate from
their ideal values. The reason for this is that
signals at half the sample rate, or 24 kHz,
undergo infinite attenuation: we in effect
have an additional null in the frequency
response at this frequency. The (not nec-
essarily disadvantageous) result of this is
that the left and right sides of the filter’s
response are not symmetric: the response
is steepened on the right-hand side.

All the filters are implemented as sixth-order
‘recursive’ or ‘MR’ filters. Just as in the ana-

logue domain, these can be made by cascad-
ing three second-order sections. Our imple-
mentation of the sixth-order filter requires
eight memory locations to store its state:
these memory locations map to capacitors
and inductors in the corresponding analogue
filter realisation. The filter also requires a
total of fifteen coefficients that determine
its characteristics. The complete set of filters
thus requires a grand total of 41 x 1 5 = 61 5
coefficients, which we store in a table. For
simplicity in programming we add a forty-
second filter which has no function except
to pass the white noise signal through unaf-
fected. This filter has index zero.

Selecting a filter is simply a matter of load-
ing the coefficient pointer so that it points
to the correct set of coefficients. The value
of this pointer is easy to calculate: if the
base address of the filter coefficient table is
A b and the filter index is F| then the pointer
address is given by A = A B + 1 5 x F,: this is
the start of the relevant coefficient block.
Here we see one of the big strengths of
digital signal processing: imagine how
complicated and costly it would be to cre-
ate a comparable analogue filter bank!
The author has a superannuated octave
and third-octave filter bank made by Bruel
and Kjaer in his laboratory: it weighs 1 5 kg
(33 lbs). We could have arranged to have
hundreds of sets of filter coefficients stored
in the DSP’s memory selected just by mov-
ing a pointer.

For the record, the forty band-pass filters
meet the specifications of BS (DIN) EN
61 260 class 0. The pink noise filter deviates

from the ideal performance by less than
0.1 dB over the frequency range from 10 Hz
to 20 kHz. The band-pass filters are capable
of attenuating stop-band signals by more
than lOOdB: such performance is difficult to
realise in an analogue circuit without inordi-
nate amounts of design effort.

The DSP code

The signal processing code itself is embed-
ded as a block in the audio loop. Even
though in this case we have no need to
read the incoming audio signal, we leave
the existing audio loop code as it is and load
the input samples as normal. This ensures
that synchronisation is maintained within
the audio loop and means that the frame-
work code is identical for all three of our
projects. The code has a total often local
parameters: Table 3 lists these along with
their valid ranges and other characteristics.
The default values of the parameters are
chosen so that the left channel emits a
sine wave with a frequency of 1 kHz and
the right channel a noise signal filtered to
one third of an octave around a centre fre-
quency of 1 kHz. In both cases the attenu-
ator halves the output sample values: this
corresponds to an attenuation of 6 dB. The
noise amplifier stage has its gain set to 0 dB
(on both channels). The default values of
the parameters are listed in Table 4 and the
files that comprise the DSP program are
given in Table 5.

Subroutines and signals

Two subroutines are called before the audio
loop is entered. The subroutine I n i t S t a t -

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SineL

SineR

NoiseL

NoiseR

NoiseGainL

NoiseGainR

NoiseShapedL

NoiseShapedR

GeneratorL

GeneratorR

OutL

OutR

Figure 4. Subroutines and signals in the audio loop.

Figure 5. Timing of the SPI port. (Source: Wikipedia)

e V a r s clears the filter state memories and
the two phase accumulators. The shift reg-
ister states are set to one of the allowable
values. Then the subroutine SetDefault-
P a r a ms sets all the parameters to the val-
ues given in Table 4.

Seven subroutines are called from within
the audio loop. Six of these are directly
involved with the audio signal processing
chain. The seventh, subroutine Filter-
S wi t c h , reads the two filter index param-
eters F i L and F i R and from these values
calculates the start addresses of the corre-
sponding filter coefficient blocks, each of
which contains fifteen entries. Although this
operation is more a translation of parameter
values than strictly speaking an audio signal
processing operation, it nevertheless must
occur within the audio loop as the param-
eters can be changed dynamically. The
other parameters are used directly and do
not require further processing within the
audio loop.

The subroutine Si neGenerator con-
tains the two independent sine wave gen-
erators for the left and right channels. The
two phase increment parameters Dp h i L
and Dp h i R determine the frequency of
the oscillators. The calculation of the sine

function using an approximating polyno-
mial is done within the macro sine. The
state variables for the sine generator sub-
routine are the two phase accumulators
I : PhaseAccuL and I : PhaseAccuR,
which contain the current phase values.
The six coefficients of the approximating
polynomial are stored in Y RAM with base
address Si n C o e f . The two sine wave out-
puts themselves are stored in memory loca-
tions y : Si n e L and y : Si n e R .

The subroutine Noi seGenerator contains
the code for the two statistically independ-
ent (for practical purposes at least) noise
signal generators for the left and right chan-
nels. Again, a macro is used for the signal
generation proper. The macro has two argu-
ments: the memory location where the shift
register contents are stored and a 24-bit
constant representing the feedback pat-
tern. The state variables are the two 24-bit
shift registers y : Noi s e L and y : Noi s e R ,
which are also the output signals of the two
noise generators.

The subroutine Filter implements the
two noise shaping filters. Each is a sixth-
order recursive, or MR, filter. We take
advantage of the library macro i i r 2 ma c
provided by Freescale (formerly Motorola).

The macro can be used to implement MR fil-
ters of any desired order and is a standard
building-block. This subroutine requires
no parameters, as the base address of the
block of fifteen coefficients has already
been computed in the subroutine Fil-
t e r S wi t c h . Two areas for state memory,
each of eight locations, are required. Their
base addresses are F s t a t e L and F s t a t e R .
The two filtered noise signals are available
aty: Noi seGai nL andy: Noi seGai nR.
The subroutine Ga i n B I o c k contains the
code that applies gain to the filtered noise
signals. The gain function is not protected
against clipping and should therefore only
be used to apply small amounts of gain.
More detailed information on this is given
elsewhere in this article. The code itself
is very straightforward: a gain of 6 dB (a
doubling of the signal level) is done using
a left shift operation. The DSP features a
barrel shifter that can shift by any num-
ber of places in constant time: this means
that we can apply a gain of any multiple of
6 dB in a single step. The two filtered noise
signals, after any gain has been applied,
are available iny: Noi seShapedL and
y: Noi seShapedR.

The subroutine Si gnal Swi tch imple-
ments the two signal source switches that

56

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One-third-octave filters and noise sianal amplification

Our signal generator can produce noise in one-third-octave and
one-octave bands by filtering white noise appropriately. If the white
noise source covering the full bandwidth from 0 Hz to 24 kHz has
a signal level of L R = 0 dB, the signal level of the filtered noise will be
lower as only a fraction of the noise power is passed through the fil-
ter. Let us look at this phenomenon in more detail. The bandwidth B
(the difference between the lower and upper cutoff frequencies) of
an ideal filter with centre frequency f m is given by

B = (2i/6 - 2-1/6) xf m = 0.231 6 xf m

for a one-third-octave filter, and

B = ( 2 i/2-2-i/2)xf m = 0.7071 xf m

for a one-octave filter. Using these bandwidth values we can calcu-
late the resulting noise power in decibels as

L 1/3 = Lr+ 10 log ,o(f m ) + 1 o log 10 (0.231 6/24000) - L R +

10log 10 (U- 50.1 547

for the one-third-octave filter, and

/-! = i R + 1 0 log 10 (U + 1 0 log 10 (0.7071 /24000) = t R +

1 0 log 10 (/m) - 45.3073

for the one-octave filter.

We collect these results in a table below.

Amplitude of filtered noise signal

Centre

One-third-octave filter

One-octave filter output

frequency

output amplitude

amplitude

fm (Hz)

1,(3 (dB)

Li (dB)

25

-36.18

31.5

-35.17

-30.32

40

-34.13

50

-33.17

63

-32.16

-27.31

80

-31.12

100

-30.15

125

-29.19

-24.34

160

-28.11

200

-27.14

250

-26.18

-21.33

315

-25.17

400

-24.13

500

-23.17

-18.32

630

-22.16

800

-21.12

1000

-20.15

-15.31

1250

-19.19

1600

-18.11

2000

-17.14

-12.3

2500

-16.18

3150

-15.17

4000

-14.13

-9.29

5000

-13.17

6300

-12.16

8000

-11.12

-6.28

10000

-10.15

12500

-9.19

16000

-8.11

-3.27

20000

-7.14

Figure A. GainL = 2, GainR = 3, no clipping.

■WMii

Figure B. Clipping causing non-linear distortion:
GainL = 3, GainR = 5.

It is easy to see that the output level rises by 1 dB per one-third of
an octave or by 3 dB per octave. If we need higher output ampli-
tudes, particularly at lower centre frequencies, we need to amplify
the signal. This is done using the parameters Ga i nL andGai nR
which operate in 6 dB steps. However, if we apply exactly the gain
implied by the above table to the signal, it is possible to cause
clipping in the signal generator. This is because the choice of gain
must be determined by the peak signal values and not by the av-
erage signal power. The values given in the table provide a useful
starting-point, however, but it is necessary to check the spectrum
of the amplified output. Figures A and B show the effect of clipping
one one-third-octave band-pass filtered noise. The signal generator
is set up to generate one-third-octave noise on both channels, the
left channel with centre frequency f m = 1 kHz and the right channel
with centre frequency f m = 80 Hz. Figure A, produced using Wave-
Lab, shows the effect of setting the gain on the left channel to 12 dB
and that on the right channel to 1 8 dB. Figure B shows the case with
the left gain set to 1 8 dB and the right gain to 30 dB. In Figure B it is
easy to see the distortion components introduced by signal clipping
alongside the band-pass filtered noise. When using a high gain it is
important to check the output spectrum to verify that clipping is not
occurring.

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DSP COURSE

Available now!

The DSP board used for all the experiments in this course, plus its
programming adaptor, are now available at a special price.

See http://www.elektor.com/noo1-92.

select between the sine wave source and
the noise source. The subroutine has two
parameters, S wL and S wR . The routine
does not have any state variables or coef-
ficient storage. The two outputs from the
switch are available aty: Gener at or L and
y : Gener at or R.

prefer a device that is rather less long in
the tooth. The microcontroller can be pro-
grammed in assembler or (more conveni-
ently) in a high-level language.

The SPI port of the DSP is operated in mas-
ter mode, and the microcontroller is set up
for operation as an SPI slave. The DSP is con-

sented below illustrates from the point of
view of the DSP bidirectional SPI communi-
cation with polling of the port status flags.
It should be possible at least to see from
the code the basics of what is required,
although some adjustments would be
needed in practice.

The final subroutine in the audio loop is

called Attenuator. This implements the

be 1 r

#HE N, x:

HCSR

; SHI disable,

S

PI reset

two attenuators that appear immediately

movep

#$00204

8, x: HCKR

; Cpol =0, Cpha

= 0

, narrow

s p i

ke

before the audio output. The attenuation

filter,

factors are given by the two parameters

; f = F 0 s c / 2 /

8

/ 10 = 0

. 92

16 MHz

A 1 p h a L and A 1 p h a R ; again, there are no

movep

#$00004

0, x: HCSR

; 8 bits, mast

e r

mode, FI

FO

of f

state variables or coefficients involved. The

bs et

#HE N, x:

HCSR

; SHI enable

attenuated signals are available at y : Ou t L
andy: Out R and are passed through to the
audio outputs.

Parameter settings

In order to modify the behaviour of the
audio signal generator while it is in opera-
tion it is necessary to alter the values in the
two sets of five parameters, one set for each
channel. As the code stands this involves
editing the subroutine Set Def aul t Par-
a ms to reflect the desired new values, re-
assembling the program and reloading it
into the DSP using the debugger. It would
be much neater if we could provide user
controls and a display to allow the param-
eter values to be changed dynamically and
sent to the DSP over its SPI port.

It would also be possible to connect a key-
pad or digital potentiometer, plus an ordi-
nary alphanumeric LCD, to the DSP itself.
However, processing user input at the same
time as generating the audio signals makes
the code more tricky: it is simpler to sep-
arate the two processes from one another
and use a microcontroller to manage the
user interface. A wide range of suitable
devices is available, and there is no great
reason to recommend a particular one. The
author’s preference for such applications is
the 68HC1 1 , whose architecture is a par-
ticularly good fit with our DSP, although
readers embarking on a new project might

move #Buffer, rO
do # N , R W_ M u C

jclr #HTDE, x: HCSR, * ; transmit register empty?

movep

x : ( r 0 )

, x : HTX

jclr

#HRNE ,

x: HCSR, *

movep

x: HRX,

y : ( r 0 ) +

R W_ M u C

figured using the registers HCSR and HCKR:
these set the clock frequency, clock polar-
ity and phase, as well as the word length,
which will normally be eight bits. Figure 5
shows the various timing options. We need
to write a parameter-setting subroutine,
which can for example be called as the ser-
vice routine for an interrupt generated by
the microcontroller. On our DSP board the
IRQC signal can be used for this purpose.

An alternative approach that avoids external
interrupts, and which is simpler if less ele-
gant, is to have the DSP periodically fetch
the parameters from the microcontroller
and update its internal variables if anything
has changed. For simplicity, the polling
interval can be set to an integer multiple of
the audio sample period. We used a similar
technique in the sine wave generator test
program described in the fourth instalment
in this series, where the audio sample clock
was divided by 1 92. The code segment pre-

r ecei ve register full?

The code segment writes and reads two
buffers of length N, a transmit buffer stored
in X RAM and a receive buffer in Y RAM,
occupying the same address range. The first
four lines of code reset the interface, con-
figure it and then enable it. The rest of the
code shows how to write to and read from
the buffer.

We end with a small suggestion for a pro-
gramming exercise. The phase increment
d(|> = 2f s /f T that is the parameter to the sine
wave generator is stored as a left-aligned
fractional value. It would be more elegant
to store the signal frequency f s as a right-
aligned integer value instead and have the
DSP carry out the necessary conversion cal-
culation. This choice of parameter represen-
tation also reduces the complexity of the
code in the user interface microcontroller.

( 110006 )

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Electronic LED Candle

You can blow it out! JP

I

LA

Imitation candles using an LED as the illuminating element are available commercially.
But here we’re describing a rather different project with a few unusual characteristics
after all, candles are meant to be blown out!

I J

-p Hi

1 rV ■■ i' i

'n!' ' , , • u

• unPo

□ll

Ij

n I

u m

^ O

K 1 1 SP *

D +5 0 +5

f > & h *?

1 K2 1

(H

By Antoine Deschamps (France)

Candlelight is by nature variable, so we’re
going to do a bit of animation to simulate
the candle flame. There will be a lighting
sequence, a blowing-out sequence, and a
few animated sequences intended to repro-
duce more or less faithfully the flickering of
a natural flame.

To produce these animations we need
a microcontroller. We went for the
PIC16F1827 from Microchip which has a
4 Kword program memory, enough for the
code to handle the application and the ani-
mation sequence definitions.

This microcontroller also has easy-to-i imple-
ment functions for handling touch keys. So
we decided to include a copper area on the
back of our PCB to create a touch pad to let
us light the candle.

To achieve our (rather over the top!) objec-
tive of being able to blow out the candle, we
have found a new use for a temperature sen-
sor in the form of an NTC thermistor.

And it works!

Puff detector

As stated above, we’re using an NTC ther-
mistor (R2 in Figure 1 ) as an air movement
detector. We’ve chosen a type in a CMS
0603 package with a nominal resistance of
220 Q @ 25 °C, a beta coefficient of 3,540 K,
and a maximum dissipation of 180 mW. A
high beta coefficient means the resistance
varies to a greater extent with variations in
temperature.

The principle of our circuit is as follows.
We may consider that a person’s breath is
appreciably similar to the ambient tempera-
ture in the room. So at first sight, blowing
on a thermistor that is already at ambient
temperature isn’t likely to make its resist-
ance change! The trick here is to pass
enough current through the thermistor to
heat it up slightly. Then a pronounced blow
will cause its temperature to drop, which
we’ll then be able to measure using one of
the microcontroller’s analogue inputs.

Our circuit includes a potential divider with
a pad resistor of 1 00 Q (R1 ). At power up

and with an ambient temperature of 25 °C,
the current is

l 25 = 5/ (100 + 220) = 16 mA.

The voltage across the thermistor is
V 25 = 220 x l 2 5 = 3.5 V, and the power dis-
sipated by the thermistor is

P 25 = V 25 x l 2 s = 3.5 x 1 6 mA = 56 mW.

We’re a long way from the maximum of
1 80 mW, but this power is enough to cause
the device’s temperature to rise, thereby
reducing its resistance, increasing the cur-
rent, and so on. After a few seconds, the
whole thing stabilises, as the oscilloscope
trace shows (Figure 2). Our software waits
for 20 s so that the temperature is properly
stabilized before taking the measurements
into account. It’s tricky to show how this
graph changes when you blow on it. After a
lot of attempts, we managed to define that
a positive variation of the order of 25 mV is
enough to detect a human breath.

6 o

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Technical specifications

• Realistic flame simulation

• Blows out

Lights via a touch pad

PIC16F1827 programmed in C, source code provided
Puff detector based on an NTC thermistor
Constructional difficulty: average

o o

a a

> >

IC1

RBO

RBI

RB2

RB3

RB4

7

SIN

2

8

9

CLK

3

10

LATCH

4

11

BLANK

21

PIC16F1827

SSOP20

RA5/MCLR/VPP

RA6

RA7

22

RSET 23

R4

0

SIN

CLK

LATCH

BLANK

SOUT

o

a

>

IC2

CAT4016

TSSOP24

RSET

o

z

o

LED1

LED2

LED3

LED4

LED5

LED6

LED7

LED8

LED9

LED10

LED11

LED12

LED13

LED14

LED15

LED16

10

11

12

13

14

15

16

17

18

19

20

GND

110644 - 11

tt Dll

tt-D4

tt D13

tl

tt

tt

44

,tt

.tt

tt

tt

tt

tt

tt

tt

D12

D2

D3

D9

D14

D1

D6

D7

D5

D8

D16

DIO

tt D15

o

o

o

o

o

o

o

•

o

o

Figure 1 . Circuit diagram of the LED candle. The component count has been minimized,
so as to fit within the area occupied by the LEDs on the top face of our PCB. The circuit is
powered from 5 V, with an electrolytic capacitor (Cl ) to clean and buffer the voltage. The
application of the microcontroller IC 1 is reduced to its simplest expression; we shall be
using the internal oscillator, since we don’t need great accuracy.

From a software point of view, it’s neces-
sary to suit the frequency of the analogue
acquisitions to the rate at which the meas-
ured signals change. We’ve used initial fil-
tering to eliminate noise, then averaging
over 1 6 successive values, so as to be able
to detect when a filtered value deviates
from the average of the 1 6 values by more
than 25 mV. The result is that you have to
blow reasonably close to the candle to blow
it out. Nonetheless, the whole thing is still
quite sensitive to draughts.

You don’t need accuracy here, as all you are
doing is comparing the temperature differ-
ences to the average of the temperatures
recorded. So there was no need to fit a volt-
age reference on the board, nor even to use
the microcontroller’s internal reference.
Hence the analogue measurement range is
delimited by the 0 V rail on the one hand,
and the supply voltage on the other.

Touch pad

The touch pad that enables us to light the
candle is connected directly to analogue
input 0 of the microcontroller IC1 (Fig-
ure 1 ). The PIC1 6F1 827 data describes the
capacitive sensing module clearly, and pro-
gramming it should not present any prob-
lem. Except for just one detail, as we don’t
immediately have any idea of the frequency
of this oscillator that is formed with the
touch pad. Remember that it’s the variation
of the capacitance of this copper pad when
a human finger approaches it that causes a
frequency variation, which is what we are
going to need to measure or, more accu-
rately, compare against a reference. The
oscillator output is connected to Timer 0,
which counts freely.

So as to be able to observe these frequen-
cies, we’ve duplicated the MSB of the
Timer 0 counter register TMRO to the out-
put connected to the test point. This then
gives us on the oscilloscope test point a fre-
quency of the order of 1 30 Hz, which drops
to below 90 Hz when a finger touches the
contact pad. This frequency corresponds to
a frequency on the eighth bit of the register
256 times higher at the input to Timer 0, i.e.
around 32 kHz.

As our application is clocked at 1 kHz (see
below), all we have to do is examine the
contents of the TMRO register at each 1 ms

cycle. TMRO has a value of around 32 when
the touch pad is free, dropping to around
23 when your finger is touching the pad.
Once it has been read, the TMRO register is
forced to 0, so as to start counting again.
In our application, we’ve set the threshold
at 26, which is quite low, and so you really
do have to put your finger on the pad for it
to be triggered. Increasing this value would
make the touch function more sensitive.

One remark in passing: when developing
a project, it’s important to make provision
whenever possible for one or more test
points. The oscilloscope too is a helpful pro-
gramming tool!

The flame

This LED application is not intended for
lighting, just to be decorative; so we’re
going to use low-current LEDs, here with a

maximum of about 2 mA. This power range
lets us choose SMD LEDs, which will make it
possible to fit them onto a relatively small
area of PCB.

Figure 2 . The temperature of the air
movement detector stabilizes after a few

seconds.

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-i» || (•: ■*!

Ih lUJi HI

luipay

|Li3ifiQ

IL'UI

ange, low current, SMD 0805, e.g. King-
bright KPHCM -201 2SECK
D1 3 = LED, red, low current, SMD 0805,
e.g. Kingbright KPHCM-201 2SURCK

Miscellaneous

K1 = 6 -pin pinheader, lead pitch 0.1 inch
(2.54 mm)

l<2 = 4-pin pinheader, lead pitch 0.1 inch
(2.54 mm)

NO O
to O •

Figure 3. The double-sided PCB carries only surface
mount (SMD) devices, but it can still be built by hand.

COMPONENT LIST

Resistors (SMD 0603)

R1 = 100ft

R2 = NTC, 220 ft, Epcos
B5731 1 V2221J60 (e.g. Farnell #129-
991 2 or RS Components # 706-2702)

R3 = 1 Okft

R4 = 27kft

Capacitors

Cl = 33pF 1 0V aluminum electrolytic,
case C, e.g. Panasonic EEE1 AA330SR

C2 = 100nF, SMD 0603

Semiconductors

IC1 = PIC16F1 827-l/SS (SSOP20),
Microchip

IC2 = CAT401 6Y-T2 (TSSOP24), ON
Semiconductor

D4 a D1 1 , D1 5 = LED, yellow, low cur-
rent, SMD 0805, e.g. Kingbright
KP-2012SYCK

D1 , D2, D3, D1 2, D14, D1 6 = LED, or-

Driving the total of 1 6 LEDs that are going
to make up the flame has been entrusted
to a specialized 1C, the CAT401 6 from ON
Semiconductor (IC2). This device incor-
porates constant current regulation for
1 6 LEDs, with the current value defined by
an external resistor (R4). The current pass-
ing in each LED channel is 50 times the cur-
rent passing through the resistor connected
to the R set pin. Given that the voltage on this
pin is regulated to 1 .2 V, with R4 = 27 kft we
have a current of 44 pA through the resistor,
and hence 2.2 mA in the LEDs. This value
offers good visibility of the animations while
ensuring acceptable luminosity levels over-
all. If you use other LEDs you may have to
tweak the value of R4.

The CAT4016 is driven via a serial connec-
tion. Four signals are used, in the direction
from the CPU to the CAT401 6:

• CLK: clock signal

• SIN: serial in data signal

• LATCH: store signal

• BLANK: signal to blank all 1 6 LEDs
simultaneously

The device data sheet illustrates the
sequencing of the signals for individually
driving the 16 LEDs. The data received,
clocked by the clock signal, are stored in
a shift register whose output is accessible
(serial output signal SOUT), which we are
not using here, but which would make it
possible to connect several devices in series
without using up more in/outputs on the
microcontroller.

The CAT401 6 uses on/off digital drive. To
make the animations a bit more fluid, we
need to be able to adjust the brightness of
the LEDs on an individual basis. The solution
is to do this in the software.

Our microcontroller is clocked at 1 6 MHz,
and as it takes four clock cycles to execute
an instruction, we have an actual speed of
4 MHz. Timer 1 has been set to produce an
interrupt every millisecond. This source of
main timing is often called a “tick system”.
At each tick, we refresh the contents of
IC2’s shift register. On our prototype, the
action of transferring the commands for
the 1 6 LEDs takes 1 60 ps, i.e. 1 6 % of the
processor time.

At this repetition rate, the human eye, or
rather the visual perception system, does
not perceive the LEDs as flashing on and
off. Very far from it, in fact — it would be
possible to reduce the refresh frequencies if
necessary, for example, to leave more CPU
time for the other software routines. So we
can create software pulse width modulation
(PWM) for each LED. In our case, we’ve con-
tented ourselves with a 5-state PWM (0 %,
25 %, 50 %, 75 %, and 1 00 %). This might not
seem very much, but the software also has
to define the patterns the LEDs are going to
make in an attempt to reproduce the flicker-
ing of a real flame. Now we’re restricted for
space in our microcontroller, so unless we
give it external memory and a method for
programming this storage space, we need
to reduce the number of states so as to be
able to define enough patterns to make our
animation pleasing.

PCB

A 17 x 60 mm board was designed (Fig-
ure 3), of which the LEDs occupy an area
1 7 x 39 mm. The lower part of the board is
reserved for the microcontroller program-
ming connector and for the power input
points.

On the top of the board there are only the
LED’s in CMS 0805 packages, i.e. a size of
2 x 1 .25 mm. We also find on this side the
temperature sensor, the NTC thermistor in
an 0603 package. This is necessary so we
can blow on it!

On the underside, you can spot at once the
“tip” of the board, which forms the touch
pad. Note too the test point TP1 , above the
microcontroller (referred to above).

To fit all the other functions on the other
side, it was necessary to resort to fine-pitch
packages. Our microcontroller comes in an
SSOP20 package with a pitch of 0.65 mm
and the LED driver was chosen in a TSSOP24
package, also with a 0.65 mm pitch. These
fine pitches should not be seen as an obsta-
cle, but rather as an effort to get closer to
the industrial techniques that are within the
reach of an amateur. An illuminated magni-
fier, a fine-tipped, temperature-controlled
soldering iron, 0.5 mm (AWG24) diameter
solder, and above all flux in a syringe! Bet-
ter not to drink too much strong coffee,
though, before you start the soldering...

The technique is well established — you
should put a tiny amount of solder on a land

62

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r — — — — — — — — — — — — — — — — — — ~ — — — — — — — — — ! — — — — — . — — ■ — — — — — — “ — — — — — > — — — — — w — — — — — — — — . — — -|

Extract of the code for initializing of Timer i for the i kHztimebase:

i T1C0N = ObOllOOlOl ; II Timer 1 configuration (Tick Interrupt Source) i

1 II 01 : Timerl source is Fosc = 16 MHz

| II 10 : Prescaler = 4 -> Ftimer = 4 MHz |

1 II 0 : Timerl oscillator circuit disabled

II 1 : Do not synchronize external clock input

i II 0: uni mpl ement ed

| II 1: T MR 1 ON = 1 - > Ti mer 1 enabl ed |

1 T1GCON = ObOOOOOOOO ; // Timer 1 gate control 1

II 0 : TMR1GE=0 -> Timer 1 counts regardless of Gate functions

TMR1H = OxFO ; II 0 x F 0 5 F is the complement of 0x0FA0 =4 0 0 0
i TMR1L = 0 x 5 F ; II Counter startup value for 1ms interrupt period (1 0 0 0 Hz)

PI El = ObOOOOOOOl ; II Interrupt sources

i II 1: T MR 1 1 E =1 -> Timerl IT source enabled i

r — — — — — — — — ______ — — — ______ — — — ~ — — — — — — ~ — — — — — — — — — — — ______ — — — — — — — — — — — — n

Extract of the code for initializing the function to handle the capacitive sensor:

OPTI ON_ REG = 0 b 0 1 1 0 1 0 0 0 ;

i II 0 : WPUEN#=0 -> Weak pull-ups enabled by individual WPUx ■

II 1 : Interrupt on rising edge of I NT (not used)

i II 1 : TMR0CS=1 -> Timer 0 counts on T0CKI i

II 0 : TMR0SE=0: Timer 0 counts of rising edge of T0CKI j

i II 1 : P S A = 1 : prescaler is not assigned to TimerO

1 / / 0 0 0: Prescaler value, 1:2 1

i II Capacitive sensing configuration

| CPSCONO = 0 b 1 0 0 0 0 1 0 1 ; j

i / / 1 : Capacitive module is enabled i

II 0 0 0 : uni mpl ement ed

i II 01 : oscillator in low- range

1 II 0: current direction status (read-only)

i II 1: T OX C 5 = 1 -> TimerO input is Capacitive Oscillator output

CPSCON1 = ObOOOOOOOO ; II Source is CPS0/RA0

_ _ _ _ _ _ ______ _ ____ _ — _ ____ _ ______ _ ____ _ _ _ _ _ J

at one end; then position the device onto
its lands and solder the tinned 1C pin. Once
you are sure it is correctly positioned, you
add some flux and solder the other pins. Sol-
der bridges will form, but it’s easy enough
to remove them using fine desolder braid.
The board has been made double-sided and
uses through-hole plating. The power rails
have been routed in the form of planes; the
+5 V plane is on the top surface, since this
rail is the common for our LEDs. Hence the
O V rail is on the underside.

The in situ programming connector K1 is
in fact a row of six through-plated holes.
The pin-out follows the order of the signals
given by the ICD3 programming interface
from Microchip (Table 1 ).

There are pads for connecting the power
(l<2) — two for the +5 V rail (pins 1 and 3),
and two for the 0 V rail (pins 2 and 4). Here

Table 1. Pin-out for the ICSP connector.
Pin 1 is marked with a square dot.

Contact

Signal

1

MCLR/Vpp

2

+5 V rail

3

0 V rail

4

ISPDAT

5

ISPCLK

6

Not used (PGM signal)

too, pad 1 is marked by a square dot. Doub-
ling up the supply pads like this is useful
when joining several boards together, to
multiply the graphical effect.

Software

As a guide, the current code written in C
occupies 84.5 % of the microcontroller’s

Flash memory, i.e. 3,460 words out of the
4,096 available. A good three-quarters of
this space is used for defining the patterns
and would require a degree of optimization
if the space issue had to be tackled.

The full source code, along with the HEX
file, is available free on the project web
page. You’ll also find there the PCB design
and you can order the PCB (bare, or built
and tested).

To your soldering irons and... Merry
Christmas!

(110644)

Software, PCB, products, etc.

www.elektor.com / 1 1 0644

elektor 12-2011

Personal Download for I © Elektor

63

TEST & MEASUREMENT

Turn your Oscilloscope
into a Reflectometer

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081176- 11

By Christian Tavernier (France)

If you’re not familiar with transmission line
theory, a reflectometer will probably seem
like some sort of magical device to you. But
using one, you can find out automatically
how far a fault is from one end of a cable,
without having to physically access the
spot. It is used as shown in the figure.

A generator is connected to both the oscil-
loscope and the cable under test (CUT),
which it drives with very fast rise-time
pulses. Now transmission line theory tells
us that if the cable is terminated in its char-
acteristic impedance, and hence, if it is in
good condition, no pulse will be reflected
back from the far end of it. And so the oscil-
loscope displays only the outgoing pulse.
However, if the cable is mismatched,
whether by a short-circuit or an open-circuit
(cable cut), the transmitted pulse is subject
to spurious reflections, and the oscilloscope
will then display two pulses: the outgoing
one, and the reflected one. We can tell how
far the fault is from the near end of the
cable simply by measuring the time delay
between them.

Obviously, such a device is incredibly use-
ful to professionals, who can avoid having
to change great lengths of cable, since they
can very easily find the exact location of the
fault. But it can also be useful for amateurs
— for example, when installing network
cabling, or finding out whereabouts your
TV aerial downlead is broken.

Sadly, a reflectometer is usually beyond the
reach of amateurs because of its high price
tag, since, in orderto produce a stand-alone
instrument, it usually includes the pulse
generator with the oscilloscope, as well as
a computer section that takes care of cal-
culating the distance to the fault. But as
long as you already have an oscilloscope,
and you are prepared to do a simple ‘rule-
of-three’ calculation with your calculator,
you can build the reflectometer we’re sug-
gesting here for around £/€ 20. But don’t
imagine from the price that this is going to
be a cheapskate instrument! It will enable
you to make the same measurements as
its professional counterparts, as shown for
example in the oscilloscope traces illustrat-
ing this article.

Our reflectometer contains just a single 1C,
an AC (Advanced CMOS) hex inverter. ICIa
is wired as an astable oscillator with a very
short mark/space ratio, thanks to diode
D2. In this way, it generates very narrow
pulses at a relatively low rate. The width
of these pulses can be adjusted to various
fixed values via SI . For the shortest cables,
you need very short pulses, otherwise the
reflected pulse arrives before the outgoing
pulse has ended, and the oscilloscope trace
is unusable. For longer cables, on the other
hand, there isn’t enough energy in those
very short pulses for the reflected pulse to

be properly visible, and so we need to use
wider pulses that contain more energy.

In order to be able to drive the cable under
the correct conditions and at an imped-
ance as close as possible to its characteris-
tic impedance, ICI’s other five inverters are
wired in parallel; hence the circuit output
impedance is determined mainly by R3-
R6, to which series resistors (R8 or R9) can
be added, depending on whether K1 , K2, or
l<3 is fitted. So we have three output imped-
ances available: 50 £1 with K1 , 75 £1 with l<2,
and 1 00 Cl with K3, so that the circuit can be
matched to the commonest cables.

64

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TEST & MEASUREMENT

The 6 V power rail should be provided by
either a bench supply, if you’re in the work-
shop, or a set of four 1 .5 V batteries for
portable use. Diode D1 protects the circuit
against reversed polarity.

In order for our reflecto meter to operate in
a stable fashion — the only way to guaran-
tee accurate measurements — we recom-
mend building it on the PCB we’ve designed
for it [1 ]. This has the advantage of minimiz-
ing wiring, as J1 and SI mount directly onto
it. SI is a vertical PCB-mounting type from
Lorlin, with the part no. PT6422/BMH.

Even though the output uses a BNC socket,
the circuit isn’t only designed for coaxial
cables, since the output impedance can be
adjusted using K1 , K2, and K3. So for other
types of cables you’ll need to use a suitable
BNC adaptor. The instrument is very easy to
use, like this:

Fit K1 (50 a), K2 (75 Q), or l<3 (100 Q)
according to the impedance of the cable
being tested. Connect the circuit up to
the input of an oscilloscope and to the
cable under test using a suitable T-piece,
as indicated in the block diagram. Then
turn the circuit on, with SI in position 1 ,
for example, and adjust the oscilloscope
so as to view the outgoing pulse.

If the cable is in good condition and cor-
rectly terminated, you will see only single
pulses, as shown in Trace 1 . If the cable
is broken, i.e. open-circuited, you’ll see a
reflected pulse of the same polarity as the
outgoing pulse, as shown in Trace 2. If the
cable is short-circuited, you’ll see a reflected
pulse of inverted polarity compared to the
outgoing pulse, as shown in Trace 3.

In either of the last two situations, all you
have to do is measure the time between
the rising edges of the two pulses (191 ns
in our example) in order to determine how
far the fault is from the measuring end of
the cable. All you need to know is that sig-
nals travel at approx 200 m/ps in a coax-
ial cable, and that the pulse has had to
make a return trip to the fault and back.
So the distance is given by the equation
D = (Vx T) I 2, where D is the distance in
metres, Vis the speed in the cable in m/
ps, and T is the time between the two ris-
ing edges, expressed in ps. In our exam-
ple, the time measured was 191 ns, so the
fault was at 1 9.1 m from the near end of

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the cable.

Do note that if the fault is not clear-cut, or
for the shortest pulses generated by the
circuit, the signals may be quite badly dis-
torted, as shown in Trace 4. However, it’s
still perfectly possible to measure the time
between the two rising edges, as shown
by this example, where a fault was located
3.8 m from the end of the cable.

Finally, if you want to make accurate meas-
urements, you can use the ‘true’ value of

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the signal propagation speed in your cable,
in place of the average value given above. All
you have to do is look it up in the cable data
sheet, where it ought normally to be given.

( 081176 -I)

Internet Link

[1 ] www.elektor. com/081 1 76

Download

081 176-1 : PCB layout (.pdf), from [1 ]

elektor 12-2011

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65

MICROCONTROLLERS

USB Data Logger

Store serial data conveniently, safely

By Thomas Fischl (Germany)

This neat design allows you to
use a standard USB memory stick
to store data in a microcontroller
based system. Memory sticks provide a
large volume of low cost, portable, non-volatile
memory space. For this application the memory
stick simply plugs into the data logger system which acts
as a host USB controller and has the ability to log or store
all serial data sent to it. Both of these tasks are handled
with ease by a PIC24FJ64GB002 microcontroller from Microchip.

Features

• USB 2.0 compatible

• Supports data rate up to 12 Mbit/s

• Connection to the host:

+5 V, GND, pC-Tx

• A file stored on the memory stick
configures the UART

• Open-Source firmware

• Power consumption:

+5 V, 50 to 80 mA

These days even the most basic microcon-
troller will have a built-in serial data inter-
face (UART). This would typically be used
to transfer configuration parameters from
a control computer or to send information
about the microcontroller’s operational sta-
tus. Quite often a microcontroller system
may be required to collect data over a long

period of time. In this situation it is usually
impractical to permanently hook up a PC to
continually store the measurement/sensor
data; the environment may not be suitable
and the relatively high power requirements
make this a wasteful solution.

The firmware of the existing microcon-
troller system could be adapted to perform
the data logging function but may require
additional memory (both EPROM and RAM)
to handle the task.

The USB data logger described here is a low-
energy, universal solution to the problem. It
takes all the serial data sent from an exter-
nal microcontroller system and stores it in
a file on a USB memory stick which can be
analysed later with a PC.

Hardware

The circuit (Figure 1 ) consists of little more
than a PIC 24 FJ 64 GB 002 microcontroller

from Microchip. This
particular model implements USB 2.0 OTG
functionality. OTG indicates ‘On The Go’
referring to the amended USB 2.0 specifi-
cation which allows a USB device to assume
not only its traditional role as slave but also
to act as a master (host) on the bus. More
recent amendments to the protocol ena-
ble communication between two OTG
devices. For this application we just need
the USB host functionality and a standard
USB A-type connector to plug in the USB
memory stick.

The microcontroller core runs at 3.3 V
which is provided on board by voltage reg-
ulator IC 2 . The serial interface is tolerant of
input levels up to 5.5 V and is protected by
220 Q resistors connected in series with the
inputs. The 5 V input supply voltage is also
used as the bus voltage (VBUS) to power the
USB stick. A resettable fuse (FI) provides

Elektor Products & Services

• PCB, order code 110409-1 • PCB artwork file (.pdf): file #110409-1, free download at [1]

• Programmed PIC microcontroller: #110409-41 • Firmware: file# 110409-11.zip, free download at [1]

66

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12-2011 elektor

MICROCONTROLLERS

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110409 - 11

Figure 1 . The USB serial data logger circuit basically consists of a microcontroller

functioning as a USB host.

some protection if an external USB device
draws too much current.

LED D1 and push button SI connect directly
to microcontroller pins. The LED flashes to
indicate data transfer and the push button is
used to terminate the data storage process.
The 6-way pin header l<3 allows the micro-
controllerto be programmed in-circuit and
is compatible with standard programming
adapter tools such as those used in PICkit
3 and ICD2/ICD3 from Microchip. Jumper
JPI is not used in the current version of
the firmware but may be employed in the
future when newer versions of the firmware
become available.

The circuit can be built on the PCB (Fig-
ure 2) which makes assembly very straight-
forward. All components are fitted to the
PCB component side and no SMD outlines
are used. An 1C socket can be used to fit the
microcontroller to the PCB. The fully popu-
lated Elektor prototype PCB can be seen in
Figure 3.

Software

The chip manufacturer Microchip already
has a useful number of functions available
in their ‘Microchip Application Libraries’
to support the interface of USB devices.
Included here is support for the device class
‘Mass Storage Device’ which includes USB
memory sticks. The FAT file format used by
the vast majority of memory sticks is also
supported. The firmware was designed
using MPLAB, the Microchip development
environment with help from the C30 com-
piler. All necessary programs and software
libraries are available free of charge and the
firmware source files can be downloaded
at no cost from the Elektor project web
site [1 ]. The firmware can be programmed
into the data logger microcontroller using
a PICkit 3 for example. A pre-programmer
microcontroller can also be purchased from
the project website [1] which should help
speed up construction even more.

Data flow between the UART and the file
system is performed by implementing two
software ping-pong buffers. The charac-
ters received via the serial interface are
stored sequentially in one of two buffers.
When the receive buffer is full the func-
tion of the two buffers is flipped or ‘ping-

ponged’ so that the entire contents of the
full buffer are streamed to the memory
stick while the other (empty) buffer is now
used to store received characters. When
the receiving buffer fills again the process
repeats. Streaming ‘chunks’ of data to the
memory stick in this way improves software
efficiency.

System hook up

Communication between the USB data log-
ger and external microcontroller system
occurs over the serial interface (UART). The
communication signal level from the exter-
nal system must lie in the range of 3.0 V to
5.5 V; in cases where the external system

uses standard RS232 port signal levels it will
be necessary to use a RS232/TTL signal con-
verter chip between the RS232 signals and
the data logger.

The data logger requires a supply of +5 V
which in most cases can be taken from the
external microcontroller system. The USB
memory stick current consumption varies
depending on the manufacturer but usually
lies in the range of 50 to 80 mA.
Connections between the external micro-
controller system and the USB data logger
are all made using pin header l<2. The data
logger requires just three connections on
K2 to the microcontroller system: +5 V (Pin
1 ), pC Tx/Logger Rx (Pin 9) and ground (Pin

elektor 12-2011

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67

MICROCONTROLLERS

COMPONENT LIST

Resistors IC2 = LP2950-33LPE3

R1 = 1 k£l

R2,R4,R5,R6 = 220£1
R3 = 5.6kQ

Capacitors

Cl ,C2,C7,C8,C9 = 1 0OnF
C3,C6 = 4.7 jlcF 35V radial
C4,C5 = 22pF

Semiconductors

D1 = LED, low-current, 3 mm
IC1 = PIC24FJ64GB002-I/SP (programmed,
Elektor# 110409-41)

1 0). Pins 2, 4, 6 and 8 are all tied to ground.
The second signal connection shown as (jiC-
Rx/Logger-Tx) is brought out to pin 5 but
not used by the current firmware version.
Microcontroller port pins 16 and 17 are

Miscellaneous

FI = resettable fuse, 250 mA hold current,
500 mAtrip current (Littlefuse 72R025XPR)
XI = 1 2MHz quartz crystal
K1 = USB socket, Type A, PCB mount
l<2 = 1 0-pin (2x5) pinheader, right angled
l<3 = 6 -pin pinheader
PCB# 110409-1

connected to pins 3 and 7 of l<2 via 220 Q
resistors. These additional connections are
intended for future use with modified firm-
ware to allow, for example the microcon-
troller to retrieve stored data.

Configuration

The serial communication parameters are
placed in the simple text file ‘config.txt’
stored on the memory stick. As soon as
the USB stick is recognised (during power-
up with the stick already in place or during
operation when the stick is plugged in) this
file is read and the serial interface config-
ured accordingly. Without this configura-
tion file the default standard communica-
tion parameters are: 9600 Baud, 1 start bit,
1 stop bit, no parity.

Operation

The data logger will be in recording mode
when it is powered up and a memory stick
is fitted. Short flashes from the LED indi-
cate that data is being received over the
serial interface. Received data is stored 1:1
in the ‘logging.txt’ file. Before unplugging
the memory stick it is necessary to press
the store pushbutton; this ensures that all
data held in the receive buffer is stored to
the logging file and that the file is closed
cleanly. The stored data can then be read on
any PC by plugging the memory stick in to
a free USB socket and reading the contents
of the ‘logging.txt’ file using a simple text
editor program.

Work in progress

Although the data logger design presented
here only stores data to a memory stick it is
clear that the design can easily be tweaked
to make it even more useful. An obvious
candidate would be to allow the stored data
files to be read back to the external micro-
controller system. As a stand-alone logger
it could also be programmed to automati-
cally sample the analogue and digital inputs
at pre-programmed intervals and store the
readings to memory stick. Four pins of the
1 0-pin l<2 pinheader are not currently in use
but are wired back to the controller I/O pins,
these peripheral signals can, for example be
used to implement an SPI interface or addi-
tional UART.

( 110409 )

Internet Link

Figure 2. The PCB does not use any SMDs.

[1 ] www.elektor.com/ 1 1 0409

Figure 3. The fully-stuffed Elektor prototype.

68

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cut-rate PLUS subscription!

Subscribe now or upgrade: www.elektor.com/subs

READERS PROJECT

LED Cycle Lamp

High-tech on the trail

By Thomas Finke (Germany)

The perfect bicycle lighting system
has yet to be invented. They are
either not bright enough or badly
designed so that they fall off when
you go over a bump or have wires that
snag or use dynamos that reduce your
speed to a dawdle. This design is one step nearer
the ideal. It is self contained, powered by Lithium Ion
rechargeable cells and has a dazzling 600 Lumen on tap.

On full beam the torch will run for around three hours, much longer in ‘dipped’ mode.

Although a true homebrew design this lamp
has a truly professional feel to it. The alu-
minium body is designed to be watertight
and requires some machining. The design
uses four Li-Ion cells connected in parallel,
each with a capacity of 2.2 Ah. A microcon-
troller takes care of battery management
allowing the lamp to be charged at 5 V from
either a mains adapter or car adapter.

Lights, cycle, action!

Flashing LED cycle lights are fine for the
urban commute; they are highly visible and
the batteries last a long time. If you how-
ever get the urge to explore unlit country
lanes or off-road trails then the chances are,
when the sun goes down you will quickly
discover their limitations. For the sake of
safety you need something more powerful
to warn you in good time of the road con-
ditions up ahead. Equivalent professional
cycle lighting systems are available but cost
hundreds of pounds. This self-contained

lamp operates from a single push button
to switch between high beam and dipped
beam. Conventional vehicle lamps switch
between two filaments to achieve a dipped
beam but with this design the main beam is
just reduced in brightness to avoid the risk
of dazzling oncoming vehicles. If you are
planning to take your bike further afield it
is worth checking the local cycling regu-
lations before you travel. Some countries
do not allow lamps that give out too much
light. In the UK the regulations only specify
that they should emit more than 4 Cande-
las. Whatever the regulations this robust,
versatile lamp should be more than capa-
ble of taking anything that’s thrown at it.

Operation

The lamp uses just a single push button and
operation is quite intuitive. A short press
switches the lamp on then further presses
toggle the lamp between ‘high beam’ and
‘dimmed’. A long press turns the lamp off.

The brightness of the dimmed beam can
be set by turning the lamp on with a long
press. Now it enters setup mode where fur-
ther press of PB1 cause the lamp to cycle
through increasing then decreasing levels
of brightness until the desired brightness
is reached. Before long the torch reverts to
normal operational mode.

The push button is fitted with an indicator
LED which is used here to give a visual indi-
cation of the battery’s state of charge. Peri-
odically it will issue a series of flashes (four
flashes indicating a fully charged battery).
When the voltage falls below a threshold
the lamp automatically switches to the low-
est brightness setting to prolong burn time.

The circuit

White LEDs have a forward voltage drop
of around 3.5 V and the voltage output of
a single Li-Ion cell varies from 2.7 to 4.2 V
depending on its state of charge. To operate

Note. Readers’ Projects are reproduced based on information supplied by the author(s) only.

The use ofElektor style schematics and other illustrations in this article does not imply the project having passed Elektor Labs for replication to verify claimed operation.

70

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READERS PROJECT

+ Vbatt +v batt

X7

Figure 1 . The circuit includes a microcontroller, two switched mode converters and a battery charge regulator.

a single LED from a single cell it would be
necessary to use a regulator which provides
a voltage initially below the fully charged
cell voltage but then above the cell volt-
age as it discharges. A SEPIC (single ended
primary inductance converter) is capable
of this sort of operation. The disadvantage
of this type of converter (besides the addi-
tional circuitry) is that they are relatively
inefficient. With this in mind it was decided
to use the four LEDs (CREE XR-E) connected
in series mounted on a circular PCB and fit-
ted with lens optics made for the CREE LEDs.
The regulator required to supply the neces-
sary 14 V is a simpler upwards converter
(step-up or boost converter).

The circuit diagram in Figure 1 shows that a
MAXI 6834 (U1 ) is used. The IC’s configura-
tion in this circuit is taken from an applica-
tion example in the chip’s data sheet, only
component values have been changed to
make it suitable for this application. Note
that with a LED current of 1 A and the bat-
tery voltage at its lowest level the coil must
be able to cope with an average current of

5.6 A. The maximum LED current is defined
by how many 1 Cl resistors are fitted to the
PCB for R1 0. With all five resistors in place
the combined value of RIO will be 0.2 Cl.
This will give a maximum LED current of 1 A.
The author fitted just three 1 Cl in the proto-
type to give an LED current of 600 mA. This
value produces more than adequate light
output and limits power dissipation in the
LEDs.

The PWMDIM pin is an input for the PWM
signal to dim the LEDs. This is used to
reduce the energy dissipated by the LED.
Pin 11 (UVEN) would normally be con-
nected to a voltage divider network to
sense and shutdown the chip when the sup-
ply voltage falls too low. In the circuit here it
is connected directly to port pin PB2 of the
Atmel microcontroller (3).

For circuit operation and to ensure the MOS-
FETs fully conduct when they are switched
on the MAXI 6834 (U1) requires a supply
voltage of at least 5 V. The rechargeable
cells alone have insufficient output so an
additional voltage converter type LM341 0
(U2) has been used to provide the stabi-

lised voltage (+VDRIVE). The LM3410 is
essentially a constant current regulator for
driving LEDs up to 500 mA. At the start of
this design the author’s original intention
was to use several LM341 0s to power the
LEDs but all that remains is one of these
tiny chips configured as a constant voltage
boost converter.

The Atmel ATtiny44 microcontroller (U3)
has the job of controlling all the other com-
ponents in the circuit. It generates the PWM
drive signal to enable the power LEDs to be
dimmed and provides the shutdown sig-
nals to U1 and U2 as necessary. The built-in
A/D converter measures the battery voltage
using the voltage divider network R40 and
R41 . To reduce current flow through the
voltage divider network when the lamp is
switched off the ground end of the divider
is connected to port pin PB0. It can now be
switched into a high impedance state to cut
off current flow through the voltage divider
network.

The lamp is never turned completely off; the
microcontroller, boost converter and LED

elektor 12-2011

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71

READERS PROJECT

Figure 2. A small circular PCB was designed for this project.

Figure 3. The circular double sided PCB
takes SMD components.

Figure 4. A view of the lamp internals.

driver are switched to sleep mode where
current consumption drops to around
1 00 jiA. This level is insignificant compared
to the battery capacity of 8.8 Ah. Push but-
ton PB1 produces an interrupt to the con-
troller, bringing the circuit out of sleep
mode.

Power supply

The MAXI 81 1 (U4) takes care of battery
management. The chip has been specifi-
cally designed to charge Li-Ion cells from
a USB port. The chip can handle a charging
current of approximately 500 mA so a com-
plete charge cycle will take up to 20 hours,
it would be problematic to supply a higher
current through the type of connector used
and from a safety viewpoint it would also
then be necessary to monitor the cell tem-
perature to ensure that it does not overheat.
The lamp is typically in use for only a few
hours a day and then partially recharged
overnight. The relatively long recharge time
has never been a limitation.

The battery pack has been made up from
four cylindrical Li-Ion cells wired in parallel.
These were salvaged from a broken Note-
book. If these cells were connected in series
the higher voltage would mean that the
step-up converter could be dispensed with
in the circuit but it would then be necessary
to have a higher voltage charger and pro-
vide a means to balance the cells.

With the LED current limited to 600 mA
the prototype operates for almost three
and a half hours continuously at maximum
brightness.

Construction

A double sided round PCB has been devel-
oped for this project (Figure 2). The popu-
lated board can be seen Figure 3.

Despite improvements in high power LED

efficiency over recent years it is still neces-
sary to consider energy losses in the devices
and take measures to ensure they do not
overheat. The LED module (4 x CREE XR-E
fitted to a 34 mm diameter PCB) is mounted
on a 5 mm thick aluminium disk which is in
good thermal contact with the aluminium
body where the heat is dissipated to the sur-
rounding air. The rear face of the disk also
serves as a heat sink for the power MOSFETs
in the circuit.

The lamp housing has parts turned from
round aluminium stock and a length of
50 mm aluminium tubing. The machined
body has been black anodised which turned
out to be a surprisingly unproblematic pro-
cedure. The website [1] for this project con-
tains two sketches detailing the mechani-
cal construction of the body. Figure 4
shows the mechanical construction of the
lamp: The front end with lens, LED carrier
plate, 5 mm aluminium heat sink disk, PCB,
mounting spacers, plastic board and the
battery cells.

The lamp housing must be watertight. The
front lens is fixed into position using silicon
adhesive. Both front and rear sections slide
into the tube body where rubber ‘O’ rings
provide a watertight seal. The waterproof
push button with integrated LED is glued to
the end of the lamp. The charging socket is
a recessed SMB connector. This miniature
coax connector is gold plated and is not sen-
sitive to damp conditions. The socket can
be fixed into the lamp body with waterproof
adhesive.

The lamp construction has undergone
strenuous road testing on a daily basis over
the last two years. It has proved to be both
robust and reliable and on poorly lit lanes,
indispensable.

( 100269 )

Internet Reference

[i] www.elektor.com/ 1 00269

72

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THE MAGAZINE FOR COMPUTER APPLICATIONS

GERARD’S COLUMNS

Speaking Out Loud

By Gerard Fonte(USA)

There are a number of surveys that show that the fear of pub-
lic speaking is greater than the fear of death. And, unfortunately,
most people (including engineers) will eventually find themselves
all alone in front of a lot of staring people, explaining a new product
or process. It’s not really bad as a lot of people fear.

Nearly everybody gets nervous before their presentation. But most
find that after a minute or two, it gets much easier. A lot find it
enjoyable after they get past the initial self-consciousness. It’s like
jumping into a swimming pool and finding that the water is really
nice. And, like most things, the more you do it, the easier it gets.
However, there are some people who can’t get over the early jitters.
For them the whole process seems like endless torture. These are
the people who have a true phobia about public speaking. Unfor-
tunately, these people generally can’t get accustomed to talking in
front of others no matter how many times they do it. Usually, coun-
seling is the only way to manage this, or any, phobia.

It’s Showtime

It’s useful to think of public speaking as a performance. As such, you
have to know your lines and understand the mechanics of the show.
Obviously, being prepared makes a huge difference in any undertak-
ing. Conversely, trying to improvise your whole presentation is not
likely to produce happy results. Therefore, the first tip is to practice
your presentation a number of times before you get upon stage.
However, unlike a role in a play, the monolog isn’t fixed. In fact, you
shouldn’t memorize your lines at all (or read your presentation).
If you do, you can appear wooden and uninteresting, which turns
people off. Instead you should have a set of talking points that you
want to discuss. And the nice thing is that you can simply put your
talking points on slides, so you don’t have to memorize them, either.
By putting just a few lines on a slide you also streamline the visuals.
This is important. Too many novice speakers try to cram too much
information on each slide. The result is that they are not readable
from the back of the room and you spend an inordinate amount of
time on one slide which causes people’s interest to fade. Conversely,
every time you present a new picture, the audience’s interest perks
up. That’s just human nature. So, you should only have a visual last
for no more than a minute or so. Thus, if you have a 1 5 minute pre-
sentation, you should prepare about 1 0 to 20 slides.

Like an actor, you need to have a character. By this, I mean that you
should be enthusiastic and motivated about your subject. Let’s face
it, if you aren’t excited about your show, why should anyone else be?
Standing in one place and droning on and on in a monotone is not
effective. Smiling, walking around and being (or acting) confident
makes a tremendous difference in your credibility. Yes, it is possible
to take this too far and start looking like a used-car salesman. But
in reality, this is rarely a problem. And, being over-animated at least
keeps the listeners attentive.

One on One

One very effective method of reducing the stress of public speak-
ing is to talk to one person. Pick someone in the crowd (preferably

in the middle) and pretend
that you are discussing your
topic only to him or her.

This helps you focus. It’s
easy to get overwhelmed
by a sea of faces. But if
you are just chatting with
someone it’s a lot easier. If
you can, change your indi-
vidual from time to time.

Addressing one person
for too long can make that
person uncomfortable. It’s
also useful to spread your
attention over the while
room.

Of course, there is no rule

that you can’t put a ringer in the crowd. Have a friend be present
and address him or her. This can reduce your anxiety significantly.
And, it’s certainly possible to get feedback from facial expressions
or other indicators. This lets you know how well you are doing. Hav-
ing your ally give you a thumbs-up after you just explained a difficult
topic is very comforting and reassuring.

Speak the Language

It can’t be stressed too much that you have to know your audience.
You will discuss your material differently for managers, salespeo-
ple, customers or engineers. Clearly, technical jargon and esoteric
details will be lost on salespeople. And failing to discuss the spe-
cialized aspects to a gathering of engineers will not garner much
credibility. You should know in advance who is coming to hear you
and target that group.

Of course, there will be times when there is a mixture of groups.
This often happens at a general company meeting to discuss new
projects, etc. In this case, there are a couple of things you can do.
The first is to talk to the decision makers (most likely top manage-
ment) using their vocabulary and discuss the points that concern
them. These are the most important people to you and your pre-
sentation and are the ones you have to impress. There’s nothing
wrong with being pragmatic.

The other approach is to recognize the presence of the different
groups and acknowledge them during your talk. This is more dif-
ficult and time consuming. You essentially have to translate tech-
nical terms used for the engineers into simplified concepts for the
others (or vice versa). But, if you have the time, this method can be
extremely effective. For example, you might say something like this:
“The new analyzer uses a 6-pole elliptic filter to eliminate aliasing.
What this means is that there is a special circuit that removes signals
that could cause problems for the software.” You probably won’t
have to translate every sentence like this. But, you have to make
sure that both the technical and non-technical groups get enough
information to satisfy them.

Speaking to a crowd doesn’t have to be a death-defying act.

(110680)

74

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INFOTAINMENT

Hexadoku

Puzzle with an electronics touch

If you are into puzzle solving, why not join the crowd of Elektor readers who solve the secret of Hexadoku
every month, or at least have a crack at it! We’re sure you’ll be thrilled. “Simply” enter the right numbers
in the puzzle below. Next, send the ones in the grey boxes to us and you automatically enter the prize draw
for one of four Elektor Shop vouchers. Have fun!

The instructions for this puzzle are straightforward. Fully geared to
electronics fans and programmers, the Hexadoku puzzle employs
the hexadecimal range 0 through F. In the diagram composed of
16x16 boxes, enter numbers such that all hexadecimal numbers
0 through F (that’s 0-9 and A-F) occur once only in each row, once

Solve Hexadoku and win!

Correct solutions received from the entire Elektor readership automati-
cally enter a prize draw for one Elektor Shop voucher worth £ 80.00
and three Elektor Shop Vouchers worth £ 40.00 each, which should
encourage all Elektor readers to participate.

in each column and in each of the 4x4 boxes (marked by the thicker
black lines). A number of clues are given in the puzzle and these
determine the start situation. Correct entries received enter a draw
for a main prize and three lesser prizes. All you need to do is send us
the numbers in the grey boxes.

Participate!

Before January 1, 2012, send your solution (the numbers in the grey
boxes) by email, fax or post to

Elektor Hexadoku - 1 000, Great West Road - Brentford TW8 9HH
United Kingdom.

Fax (+44) 208 2614447 Email: hexadoku@elektor.com

Prize winners

The solution of the October 201 1 Hexadoku is: D0837.

The Elektor £80.00 voucher has been awarded to Olavi Parkka (Finland).

The Elektor £40.00 vouchers have been awarded to Susanne Muller-Furrer (Switzerland),

Robert Amandine (France) and Thierry Notot (France).

Congratulations everyone!

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The competition is not open to employees of Elektor International Media, its business partners and/or associated publishing houses.

elektor 12-2011

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75

RETRONICS

RCA Cosmac Development System

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By Jan Buiting (Elektor UK&US Editorial)

As far as microprocessors are concerned my roots are in the early
1980s when all sorts of ‘hobby systems’ were around based on
competing devices like the Z80, 6502 and 8085. I’ve always hated
electronics that gets hot while doing nothing useful so I left these
NMOS current hungry micros, fan clubs and BBSs well alone and
went for a less popular 8-bit number cruncher called CDP1802
originally designed and produced by RCA, the company behind the
famous CD4000 series of logic ICs. The CMOS (hence acutely energy
friendly) 1 802 and its family of ‘Cosmac’ peripheral ICs did really
well in the USA after a cute DIY system called Cosmac ELF was pub-
lished in Popular Electronics way back in 1 976 (it was roughly the
time when Jobs & The Woz tinkered with 6502s in their Palo Alto
garage). A more sophisticated European variant called ‘Cosmicos’
was developed about four years later and that was to become my
personal ‘platform’ (see “CDP1 802 — the first micro in space”, Ele-
ktor October 2006).

In 1980, as a student, if you could lay your hands on an RCA Cosmac
data book, you were King. I managed to permanently borrow one
from a kind soul at Vekano, a former RCA distributor in Holland. Prob-
ably to fill the book and keep the marketing people happy, the last
40 or so pages of the book showed some of RCA’s software tools,
hardware, programmers, compilers (like BASIC and PL/M) and Cos-
mac development systems. Although my own DIY Cosmicos system
was pretty well equipped (48 KByte RAM and all that), ‘green’ (under
200 mA @ 5 V) and fast too (3.58 MHz), I marvelled and drooled over
the specs and (very poor) photograph promoting RCA’s top-line
product: the monumental Cosmac System IV Development System
CDP1 8S008. No price was given — I guess you had to telephone.
Depending on your hobby or interests, it may take just 30 years
before you can actually buy what you dreamt of as a youngster
or student. Two forces work to your advantage, slowly but surely:
(1 ) you make money instead of wasting it and (2) the price of the
‘desideratum/a’ drops to the level of techno junk no one wants. I’ve

always cherished my Cosmicos CDP1 802 system and all its cards
and peripherals, and a few years ago while browsing the ELF pages
at Yahoogroups I could not believe my eyes! A posting from a fel-
low countryman politely asking a mostly American audience on
the forum if anyone would like a complete Cosmac IV system. All
respectfully declined because of the colossal cost of getting the kit
shipped to the US, where it had come from in 1 981 . To cut a long
story short, I collected the complete system, paid a symbolic price
and drove it home. A load of hardware actually developed with the
system was also included, as well as documentation in binders and
software on 8-inch floppy disks. It was the first time I had to adjust
the headlights on my car to prevent dazzling oncoming traffic. I
never realized the system I had seen in a book 30 years ago was so
bulky and heavy. But Home & Mother, what a find!

The bright blue and off-white unit labelled ‘Cosmac IV’ is basically
a CRT dumb terminal talking internally to a CDP1 802 system. It
weighs only 1 7 kgs (38 lbs). Believe it or not but the ‘terminal’ is
itself a CDP1802 video system sitting between a keyboard and a
12-inch CRT. The actual development system is a separate back-
plane onto which RCA CDP1 8Sxx ‘micromodules’ are plugged like
CPU (CDP1 802), ROM, RAM, I/O, FDISK, etc. The software you want
to develop for a custom application is fully written, tested and
debugged using the ‘card nest’, until (you think) hex code is ready
to safely burn firmware (E)PROMs like the 2708 and 2716. The (E)
PROM programmer is accessible under a hinged panel. The panel
opens and closes by pressing it. People fund it funny. On the rear of
the terminal casing there’s connectors for AC power, disk, printer,
CRT EIA, SYS, EIA, MOPS EIA, spare #1 and spare #2.

The Cosmac IV terminal unit has a nostalgic bright green CRT display
that’s just perfect to read although at 24 lines of 80 characters it’s
claustrophobic compared to today’s LCD monitors. Also, the Sperry
made 73-key ASCII keyboard is a delight to listen to when typed
upon at speed, the keys being of the Hall effect type. Using the full-
screen editor (FSE) to write your code (in assembler, of course) you
hardly miss the ease and comfort of a mouse, menus, icons or the
constant distraction of the Internet!

76

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RETRONICS

IV (CDP18S008) (ca. 1978)

If you thought the Cosmac IV blue & white CRT terminal is “expen-
sive & comprehensive” and you can’t wait to start writing code and
burn ROMs, wait! There are two more ‘components’ that go into
the CDP1 8S008 system.

First, there’s a dual disk drive for 8-inch floppy (“flexible”) disks
with a gross capacity of 256 KBytes (0.025 GBytes) each. Made by
Pertec (Chatsworth & Irvine, CA) and the case cover sprayed ‘RCA
blue’ according to a leaflet I found, this monster called Model 371 2
weighs 34 kgs (75 lbs). The same drive units but in a different colour
were supplied to Altair for their 8080 based systems, and very likely
to other minicomputer manufacturers. The unit produces a horren-
dous amount of noise due to a huge extractor fan and the two disk
drive motors spinning all the time (probably to keep disk access
times within limits). A loud ‘clack’ is heard whenever a floppy disk
gets selected or released. The hum of the heads racing across on the
disk surface would make a nice ringtone. Inside the case, a control
board roughly the size of two iMacs is seen, stuffed with 1 50-odd ICs
— mostly plain TTL running at 5 V. Noisy, hot and slow as it may be,
the dual diskdrive unit turned out to work reliably after 30 years —
all 8-inch disks I got from the previous owner could be read without
problems and I am now considering starting an 8-inch-to-USB-sticl<
On Demand Conversion Service.

The third component of the system is called ‘Micromonitor’
(CDP1 8S030), where ‘micro’ definitely refers to ‘microcontroller’,
not size. It’s an aluminium suitcase, again sprayed RCA blue, con-
taining not much more than LEDs, switches and ZIF sockets. The
idea was to migrate the CPU from the customer application to the
Micromonitor (via a length of 40way ribbon cable) and then sort of
single-step the firmware to watch what the CPU lines were doing!
So, the blue suitcase not unfit for a travelling salesman appearing
on The Jetsons was intended to help debug CDP1 802 applications
“in-system, in real time, on site”! But just how? I really can’t figure
out because you soon need to view hex code and possibly enter it in

a comfortable way. A later version (CDP1 8S030A) had a detachable
display/keyboard unit that looked like a 1970s pocket calculator.
The only mass-produced CDP1 802 application circuits that seem
to have survived are a US made traffic lights system occasionally
offered on Ebay, and a 1 996 (!) Nokia UHF in-car radiotelephone that
got hacked and converted to amateur radio use. Oops, I should not
forget a home / game computer called COMX35.

Today, a small group of people still enjoy working with the CDP1 802
‘Cosmac’ CPU; they can be found within the ELF communities on the
web. Personally, I am using the Cosmac IV system occasionally to
tweak the software of my DIY hothouse climate and irrigation con-
trol based on a good old CDP1 802. 1 cheerfully use things like PL/M,
CDOS, UT5, MOPS, BASIC1 , and ASM8. The bulky disk drives and the
Micromonitor are no longer used, the former being emulated by
two SMD static RAMs with battery backup! For sure I can appreciate
30 years of progress and miniaturisation we all achieved in micro-
controller systems and components. True, all 70 kgs (1 55 lbs) worth
of CDP1 8S008 should easily fit in, say, a single Xilinx ‘Spartan’ FPGA.
I know, my Cosmac IV system really belongs in a computer museum.
On the Internet, a 1976 price of $70,000 was mentioned some-
where for a full blown CDP1 8S008 system like the one described
here. I have no way of verifying. All I know is that the previous owner
never guite managed to recoup the cost of his system through
developing, selling and supporting highly specialized applications
commissioned by clients including government institutions. It’s a
sobering thought that today microcontroller development systems
are available at give-away prices from the manufacturers.

If any Retronics reader out there has any original RCA Cosmac CDP-
1 8Sxx disks containing software tools or higher level programming
languages, please let me know. The same for a CDP1 8S021 Micro-
terminal running UT5.

(110528)

Retronics is a monthly column covering vintage electronics including legendary Elektor designs. Contributions, suggestions and
reguests are welcomed ; please send an email to editor@elektor.com

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• Ethernet, CAN, USB, TCP/IP, Zigbee, Bluetooth
programming

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78

Personal Download for I © Elektor

12-2011 elektor

products and services directory

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TYDER

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VIRTINS TECHNOLOGY

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SHOWCASE YOUR COMPANY HERE

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79

SHOP BOOKS, CD-ROMs, DVDs, KITS & MODULES

Going Strong

A world of electronics
from a single shop!

Creative solutions for all areas of electronics

311 Circuits

31 1 Circuits is the twelfth volume in Elektor’s renowned 30x series. These Summer Circuits com-
pilation books have been bestsellers for many years. This brand new book contains circuits, design
ideas, tips and tricks from all areas of electronics: audio & video, computers & microcontrollers,
radio, hobby & modelling, home & garden, power supplies & batteries, test & measurement,
software, not forgetting a section ‘miscellaneous’ for everything that doesn’t fit in one of
the other categories. 31 1 Circuits offers many complete solutions as well as useful starting points
for your own projects. Both categories and anything in between represent a veritable fountain
of inspiration for cultivating your own ideas and learning about electronics. This book deserves
a place notfarfrom the workbench!

420 pages • ISBN 978-1-907920-08-0 • £29.50 • US$47.60

□ lcktor LabWorX 1

LabWorX: Straight from the Lab to your Brain

Mastering the l 2 C Bus

Mastering the l 2 C Bus is the first book in
the LabWorX collection. It takes you on an
exploratory journey of the l 2 C Bus and its
applications. Besides the Bus protocol
plenty of attention is given to the practical
applications and designing a solid system.
The most common l 2 C compatible chip
classes are covered in detail. Two experi-
mentation boards are available that allow
for rapid prototype development. These
are completed by a USB to l 2 C probe and a
software framework to control l 2 C devices
from your computer.

248 pages • ISBN 978-0-905705-98-9
£29.50 • US$47.60

Linux

PC-tHHd
Measurement electronics

A highly-practkai guide

Linux - PC -based
Measurement Electronics

If you want to learn howto quickly build
Linux-based applications able to collect,
process and display data on a PC from va-
rious analog and digital sensors, howto
control circuitry attached to a computer,
then even how to pass data via a network
or control your embedded system wire-
lesslyand more-then this isthe bookfor
you! The book covers both hardware and
software aspects of designing typical em-
bedded systems using schematics, code
listings and full descriptions.

264 pages • ISBN 978-1-907920-03-5
£29.50 • US$47.60

8o

Prices and item descriptions subject to change. E. & O.E

Personal Download for I © Elektor

12-2011 elektor

Controller
Area Network

Free mikroC compiler CD-ROM included

Controller Area
Network Projects

The aim of the book is to teach you the
basic principles of CAN networks and in
addition the development of microcon-
troller based projects using the CAN bus.
You will learn howto design microcontrol-
ler based CAN bus nodes, build a CAN bus,
develop high-level programs, and then
exchange data in real-time overthe bus.
You will also learn howto build microcon-
troller hardware and interface it to LEDs,
LCDs, and A/D converters.

260 pages • ISBN 978-1-907920-04-2
£29.50 • US$47.60

Talk with your computer

Design your own PC
Voice Control System

This book guides you through practical
speech recognition, speech annunciation
and control of really useful peripherals. It
details a project which will enable you to
instruct your computer using your voice
and get it to control electrical devices, tell
you the time, checkyour share values, get
the weather forecast, etc. and speak it all
back to you in a natural human voice. If
you are interested in the practical techno-
logy of interfacing with machines using
voice, then this book is your guide!

216 pages • ISBN 978-1-907920-07-3
£29.50 • US$47.60

Design you* - own

Enhanced second edition: 180 new pages

Design your own
Embedded Linux
Control Centre on a PC

"\

The main system described in this book re-
uses an old PC, a wireless mains outlet with
three switches and one controller, and a
USB webcam. All this is linked together by
Linux. This book will serve up the basics of
setting upa Linuxenvironment- including
a software development environment -so
it can be used as a control centre. The book
will also guide you through the necessary
setup and configuration of a Webserver,
which will be the interface to your very own
home control centre. New edition enhance-
ments include details of extending the ca-
pabilities of your control center with ports
for a mobile phone (for SMS messaging)
and the Elektor “thermo snake” for low-
cost networked real-time thermal moni-
toring of your house and outbuildings. Now
you can additionally also send all kinds of
useful temperature and sensor warnings to
a mobile phone. All software needed will
be available at the Elektor website.

41 6 pages • ISBN 978-1-907920-02-8
£34.50 • US$55.70

More information on the
Elektor Website:

www.elektor.com

Elektor

Regus Brentford
1 000 Great West Road
Brentford
TW8 9HH
United Kingdom
Tel.: +44 20 8261 4509
Fax: +44 20 8261 4447
Email: order@elektor.com

Circuits, ideas, tips and tricks from Elektor

cd 1001 Circuits

This CD-ROM contains more than 1 000 cir-
cuits, ideas, tips and tricks from the Sum-
mer Circuits issues 2001 -201 0 of Elektor,
supplemented with various other small
projects, including all circuit diagrams,
descriptions, component lists and full-
sized layouts. The articles are grouped
alphabetically in nine different sections:
audio & video, computer & microcontrol-
ler, hobby & modelling, home & garden,
high frequency, power supply, robotics,
test & measurement and of course a sec-
tion miscellaneous for everything that
didn’t fit in one of the other sections. Texts
and component lists may be searched with
the search function of Adobe Reader.

ISBN 978-1 -907920-06-6
£34.50 • US $55.70

More than 70,000 components

cd Elektor’s Components
Database 6

This CD-ROM gives you easy access to de-
sign data for over 7,800 ICs, more than
35,600 transistors, FETs, thyristors and tri-
acs,justunder25,000diodesand 1,800op-
tocouplers.The program package consists
of eight databanks covering ICs, transistors,
diodes and optocouplers. A further eleven
applications cover the calculation of, forex-
ample, zener diode series resistors, voltage
regulators, voltage dividers and AMV’s. A
colour band decoder is included for deter-
mining resistor and inductorvalues. All da-
tabank applications are fully interactive,
allowing the user to add, edit and complete
component data.

ISBN 978-90-5381 -258-7
£24.90 • US $40.20

V J

elektor 12-2011

Personal Download for I © Elektor

81

SHOP BOOKS, CD-ROMs, DVDs, KITS & MODULES

ATM18 board

cd ATM1 8 Collection

This CD-ROM contains all articles from the
popular ATM18-CC2 series published in
Elektor magazine. From RFID Reader and
Bluetooth linking right up to a chess com-
puter! Project software and PCB layouts in
PDF format are included. What’s more, this
CD also contains a Bascom AVR program-
ming course and helpful supplementary
documentation.

ISBN 978-0-905705-92-7
£24.50 • US $39.60

Improved Radiation
Meter

(November 201 1)

All that’s required to measure radiation
is a simple PIN photodiode and a suitable
preamplifier circuit. Elektor presents an
optimised preamplifier and a microcon-
troller-based counter. The microcontroller
takes care of measuring time and pulse
rate, displaying the result in counts per
minute. This device can be used with diffe-
rent sensors to measure gamma and alpha
radiation. It is particularly suitablefor long-
term measurements and for examining
weakly radioactive samples.

Kit of parts incl. display and
programmed controller

All articles in Elektor Volume 201 0

dvd Elektor 2010

This DVD-ROM contains all editorial arti-
cles published in Volume 2010 of the
English, Spanish, Dutch, French and Ger-
man editions of Elektor. Using the supplied
Adobe Reader program, articles are pre-
sented in the same layout as originally
found in the magazine. An extensive
search machine is available to locate
keywords in any article. With this DVD you
can also produce hard copy of PCB layouts
at printer resolution, adapt PCB layouts
using your favourite graphics program,
zoom in / out on selected PCB areas and
export circuit diagrams and illustrations
to other programs.

ISBN 978-90-5381 -267-9
£23.50 • US $37.90

Art.# 11 0538-71 • £35.50 • US$57.30

FT232R USB/
Serial Bridge/BOB

(September 201 1)

You’ll be surprised first and foremost by
the size of this USB/serial converter— no
larger than the moulded plug on a USB ca-
ble! And you’re also bound to appreciate
that fact that it’s practical, quickto imple-
ment, reusable, and multi-platform —
and yet for all that, not too expensive!
Maybe you don’t think much of the vario-
us commercially-available FT232R-based
modules. Too expensive, too bulky, badly
designed, ... That’s why this project got
designed in the form of a breakout board
(BOB).

PCB, assembled and tested
Art.# 11 0553-91 • £12.90 • US$20.90

82 Prices and item descriptions subject to change. E. &O.E

Personal Download for I © Elektor

Audio DSP Course

(September 201 1)

This DSP board is the platform for the
applications described in our Audio DSP
Course. It is also intended to enable you
to develop your own initial digital audio
signal processing applications. The DSP
board can be used stand-alone as is, and
even though it is an ideal learning plat-
form, with its 24-bit signal processing
capability for sampling rates up to
1 92 kHz and its high-performance inter-
faces, it is also suitable for applications
with very stringent quality requirements
for both signal to noise ratio and DSP
computing power.

Populated and tested DSP board

Art.# 11 0001 -91 • £115.70 • US$186.70

USB Long-Term
Weather Logger

(September 201 1)

This stand-alone data logger displays
pressure, temperature and humidity rea-
dings generated by l 2 C bus sensors on an
LCD panel, and can run for six to eight
weeks on three AA batteries. The stored
readings can be read out over USB and
plotted on a PC using gnuplot. Digital
sensor modules keep the hardware sim-
ple and no calibration is required.

Kit of parts incl. PCB , controller , humidity
sensor and air pressure sensor modules

Art.# 100888-73 • £31.10 • US$50.20

y

12-2011 elektor

£ US$

December 2011 (No. 420) L

+ + + Product Shortlist December: See www.elektor.com + + +

November 2011 (No. 41 9)
Improved Radiation Meter

110538-41 .... Programmed controller ATmega88PA-PU

9.35....

....15.10

110538-71 .... Kit of parts incl. display and

programmed controller

...35.50....

....57.30

Simple Bat Detector

110550-1 PCB, bare

8.85....

....14.30

OnCE/JTAG Interface

1 1 0534-91 .... Programmer board, assembled and tested

...35.60...,

....57.30

Here comes the Bus! (9)

110258-1 Experimental Node board

5.30....

8.60

1 1 0258-1 C3 .. Printed circuit board 3x print Experimental Node ..

...11.50....

....18.60

1 1 0258-91 .... USB/RS485 Converter, ready made module

...22.20....

....35.90

Dual Linear PSU for Model Aircraft

081064-1 Printed circuit board

...14.50....

....23.80

October 2011 (No. 41 8)

Versatile Board for AVR Microcontroller Circuits

1 00892-1 Printed circuit board 1 1 .55 1 8.70

Audio DSP Course (4)

110001-91 ....PCB, populated and tested DSP board 115.70 186.70

1 1 0001-92 .... Bundle DSP board (1 1 0001 -92)

with Programmer (11 0534-91) 215.00 133.50

Here comes the Bus! (8)

1 1 0258-1 Experimental Node board 5.30 8.60

1 1 0258-1 C3 .. Printed circuit board Experimental Nodes (3 PCBs).... 1 1 .50 1 8.60

1 1 0258-91 .... USB/RS485 Converter, ready made module 22.20 35.90

September 2011 (No. 41 7)
eC-Reflow-Mate

100447-91 .... Professional SMT reflow oven 2 170. 00. ..3495. 00

USB Long-Term Weather Logger

100888-1

.Printed circuit board

..16.00 ...

...25.90

100888-41 ...

. Programmed controller ATMEGA88-20PU

....8.85 ...

...14.30

100888-71 ...

. HH10D humidity sensormodule

.... 7.10....

...11.50

100888-72...

. HP03SA air pressure sensor module

.... 5.75....

9.30

100888-73...

. Kit of parts incl. PCB, controller, humidity sensor

and air pressure sensor modules

..31.10....

...50.20

I 2 C Sensors

100888-71 ...

. HH10D humidity sensormodule

.... 7.10....

...11.50

100888-72...

. HP03SA air pressure sensor module

.... 5.75....

9.30

E-Blocks go Twitter

EB003

. E-blocks Sensor board

..21.60....

...34.90

EB005

. E-blocks LCD board

..24.00....

...38.80

EB006

. E-blocks PIC Multiprogrammer

.. 72.00....

.116.20

EB007

. E-blocks Switch board

..14.40....

...23.30

EB059

. E-blocks Servo board

..14.40....

...23.30

EB069

. E-blocks Wireless LAN board

132.00....

.212.90

TEDSSI4

. Flowcode4fordsPIC/PIC24

178.80....

.288.40

FT232R USB/Serial Bridge/BOB

110553-91 ...

. PCB, assembled and tested

..12.90....

...20.90

Here Comes the Bus! (7)

110258-1

. Experimental Node board, bare

.... 5.30....

8.60

11 0258-1 C3.

. 3 x Experimental Node board, bare

..11.50....

...18.60

110258-91 ...

. USB/RS485 Converter, ready made module

..22.20....

...35.90

J2B: Universal MMI Module using ARM Cortex-M3

050176-74...

. Enclosure Bopla Unimas 1 60

....8.85....

...14.30

110274-71 ...

. Tested PCB with LPC1 343 microcontroller, crystal,

3V3 voltage regulator, LCD interface & USB interface mounted.

LED and headers

..35.00....

...56.50

110274-72...

. LC-display 4x20 characters

(HD44780 compatible)

....8.90....

...14.40

V J

Bestsellers

( . C rmtrnllor Ama MohA/nrl/ PrnioH-c i

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Controller Area Network Projects

ISBN 978-1 -907920-04-2 .... £29.50 US $47.60

31 1 Circuits

ISBN 978-1 -907920-08-0 .... £29.50 US $47.60

Design your own

PC Voice Control System

ISBN 978-1 -907920-07-3 .... £29.50 US $47.60

Mastering the l 2 C Bus

ISBN 978-0-905705-98-9.... £29.50 US $47.60

Linux - PC-based measurement electronics

ISBN 978-1 -907920-03-5 .... £29.50 US $47.60

CD 1001 Circuits

ISBN 978-1 -907920-06-6.... £34.50 US $55.70

DVD Elektor 1 990 through 1 999

ISBN 978-0-905705-76-7 .... £69.00 ...US $1 1 1 .30

DVD Elektor 2010

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CD ATM1 8 Collection

ISBN 978-0-905705-92-7.... £24.50 US $39.60

o

1

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4

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ISBN 978-90-5381 -258-7 .... £24.90 US $40.20

FT232R USB/Serial Bridge/BOB

Art. # 1 1 0553-91 £1 2.90 US $20.90

USB Long-Term Weather Logger

Art. # 1 00888-73 £31.10 US $50.20

Improved Radiation Meter

Art. # 1 1 0538-71 £35.50 US $57.30

Audio DSP Board

Art. # 1 1 0001 -91 £1 1 5.70 ...US $1 86.70

Pico C Meter

Art. # 1 00823-71 £73.40 ...US $1 1 8.4Q/

Order quickly and securely through

www.elektor.com/shop

or use the Order Form near the end
of the magazine!

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83

COMING ATTRACTIONS

NEXT MONTH IN ELEKTOR

AC Powerline Frequency Meter

The frequency of the AC grid voltage is nominally 50 Hz or 60 Hz. The actual value varies
a little, depending on energy supply and consumption. With an accurate measurement of
the frequency you can determine what’s happening on your local power grid. This handy
‘frequency magnifier’ can detect even the smallest changes due to peak load instants like
everyone in the UK plugging in the kettle after EastEnders.

Andropod

Android devices are ideally suited to use in conjunction with embedded electronics. For
little money they offer access to a display, computing, various interfaces and sensors. The
big problem however is to pinpoint the connectivity between the Android device and the
hardware connected to it. The Elektor Andropod was developed specifically with that in
mind: it’s an Android USB interface with host functionality

Digital VU Meter

In Party of our DSP course, the DSP board gets combined with an LED VU meter. This setup
enables the levels of two digital audio signals to be visualised with great accuracy. The
VU meter employs special LED driver ICs from Texas Instruments and has a display made
from 2x40 LEDs. If you think that’s not enough, you can simply connect multiple boards
in series.

Article titles and magazine contents subject to change; please check the Magazine tab on www.elektor.com
Elektor UK/European January 2012 edition: on sale December 75, 2077. Elektor USA January 2012 edition: published December 7 2, 2077.

w.elektor.com www.elektor.com www.elektor.com www.elektor.com www.elektor.com wv

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Also on the Elektor website:

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All magazine articles back to volume 2000 are available individually in pdf format against e-credits. Article summaries and compo-
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shown, including software downloads, hyperlinks, circuit boards, programmed ICs and corrections and updates if applicable.

In the Elektor Shop you’ll find all other products sold by the
publishers, like CD-ROMs, DVDs, kits, modules, equipment,
tools and books. A powerful search function allows you to hAl
search for items and references across the entire website.

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i2-20iie lektor

Description Price each Qty. Total Order Code

311 Circuits £29.50

Design your own PC Voice

Control System £29.50

Controller Area Network Projects £29.50

LabWorX - Mastering the PC Bus £29.50

Linux - PC-based Measurement Electronics £29.50

CD 1001 Circuits £34.50

Sub-total

P&P

Prices and item descriptions subject to change.

The publishers reserve the right to change prices

without prior notification. Prices and item descriptions Total paid

shown here supersede those in previous issues. E. & O.E.

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Elektor

Reg us Brentford
1 000 Great West Road
Brentford TW8 9HH
United Kingdom

Tel.: +44 20 8261 4509
Fax: +44 20 8261 4447
www. e I e kto r. co m
service@elektor.com

ORDERING INSTRUCTIONS, P&P CHARGES

All orders, except for subscriptions (for which see below), must be sent BY POST or FAX to our Brentford address using the Order Form
overleaf. Online ordering: www.elektor.com/shop

Readers in the USA and Canada should send orders, except for subscriptions (for which see below), to the USA address given on the
order form. Please apply to Elektor US for applicable P&P charges. Please allow 4-6 weeks for delivery.

Orders placed on our Brentford office must include P&P charges (Priority or Standard) as follows: Europe: £6.00 (Standard) or £7.00
(Priority) Outside Europe: £9.00 (Standard) or £1 1 .00 (Priority)

HOW TO PAY

All orders must be accompanied by the full payment, including postage and packing charges as stated above or advised by Customer
Services staff.

Bank transfer into account no. 4027021 1 held by Elektor International Media BV with The Royal Bank of Scotland, London.

IBAN: GB96 ABNA 4050 3040 2702 1 1 . BIC: ABNAGB2L. Currency: sterling (UKP).

Please ensure your full name and address gets communicated to us.

Cheque sent by post, made payable to Elektor Electronics. We can only accept sterling cheques and bank drafts from UK-resident
customers or subscribers. We regret that no cheques can be accepted from customers or subscribers in any other country.

GCredit card VISA and MasterCard can be processed by mail, email, web, fax and telephone. Online ordering through our website is
SSL-protected for your security.

COMPONENTS

Components for projects appearing in Elektor are usually available from certain advertisers in this magazine. If difficulties in the supply
of components are envisaged, a source will normally be advised in the article. Note, however, that the source(s) given is (are) not
exclusive.

TERMS OF BUSINESS

Delivery Although every effort will be made to dispatch your order within 2-3 weeks from receipt of your instructions, we can not guaran-
tee this time scale for all orders. Returns Faulty goods or goods sent in error may be returned for replacement or refund, but not before
obtaining our consent. All goods returned should be packed securely in a padded bag or box, enclosing a covering letter stating the
dispatch note number. If the goods are returned because of a mistake on our part, we will refund the return postage. Damaged goods
Claims for damaged goods must be received at our Brentford office within 10-days (UK); 14-days (Europe) or 21 -days (all other countries).
Cancelled orders All cancelled orders will be subject to a 1 0% handling charge with a minimum charge of £5.00. Patents Patent protection
may exist in respect of circuits, devices, components, and soon, described in our books and magazines. Elektor does not accept responsi-
bility or liability for failing to identify such patent or other protection. Copyright All drawings, photographs, articles, printed circuit boards,
programmed integrated circuits, diskettes and software carriers published in our books and magazines (other than in third-party adver-
tisements) are copyright and may not be reproduced or transmitted in any form or by any means, including photocopying and recording,
in whole or in part, without the prior permission of Elektor in writing. Such written permission must also be obtained before any part of
these publications is stored in a retrieval system of any nature. Notwithstanding the above, printed-circuit boards may be produced for
private and personal use without prior permission. Limitation of liability Elektor shall not be liable in contract, tort, or otherwise, for any loss
or damage suffered by the purchaser whatsoever or howsoever arising out of, or in connexion with, the supply of goods or services by Elektor
other than to supply goods as described or, at the option of Elektor, to refund the purchaser any money paid in respect of the goods. Law Any
question relating to the supply of goods and services by Elektor shall be determined in all respects by the laws of England.

January 201 1

SUBSCRIPTION RATES FOR ANNUAL SUBSCRIPTION

United Kingdom & Ireland

Standard

£52.50

Plus

£65.00

Surface Mail

Rest of the World

£67.00

£79.50

Airmail

Rest of the World

£84.50

£97.00

USA & Canada

| Seewww.elektor.com/usaforspecialoffers |

HOW TO PAY

Bank transfer into account no. 4027021 1 held by Elektor
International Media BV with The Royal Bank of Scotland, London.
IBAN: GB96 ABNA 4050 3040 2702 1 1 . BIC: ABNAGB2L.

Currency: sterling (UKP). Please ensure your full name and address
gets communicated to us.

Cheque sent by post, made payable to Elektor Electronics. We can
only accept sterling cheques and bank drafts from UK-resident cus-
tomers or subscribers. We regret that no cheques can be accepted
from customers or subscribers in any other country.

Credit card VISA and MasterCard can be processed by mail, email,
web, fax and telephone. Online ordering through our website is
SSL-protected for your security.

SUBSCRIPTION CONDITIONS

The standard subscription order period is twelve months.

If a permanent change of address during the subscription
period means that copies have to be despatched by a more
expensive service, no extra charge will be made. Conversely,
no refund will be made, nor expiry date extended, if a change
of address allows the use of a cheaper service.

Student applications, which qualify for a 20% (twenty per
cent) reduction in current rates, must be supported by
evidence of studentship signed by the head of the college,
school or university faculty.

A standard Student Subscription costs £42.00, a Student
Subscription-Plus costs £54.50 (UK only).

Please note that new subscriptions take about four weeks
from receipt of order to become effective.

Cancelled subscriptions will be subject to a charge of 25%
(twenty-five per cent) of the full subscription price or £7.50,
whichever is the higher, plus the cost of any issues already
dispatched. Subsciptions cannot be cancelled after they
have run for six months or more.

Personal Download for I © Elektor

January 201 1

dsPIC/PIC24-Bundle

Advantageous hardware/software solution for rapid project development

This solution is perfect for anyone wanting to
develop systems based around Microchip’s
powerful 16 bit core products. The pack is
supplied with a dsPIC30F2011 device, and is
fully compatible with the full range of E-block
boards and accessories. Datasheets on each
individual item are available separately.

Contents:

• Flowcode 4 for dsPIC/PIC24 (Professional Version)

• USB dsPIC/PIC24 Microcontroller Multiprogrammer

• LCD Board

• LED Board

• Switch Board

• Plug top power supply

• USB cable

Bundle Price:

Only £299.00

Order now at www.elektor.com/dspic-bundle

15% DISCOUNT to the
sum of the individual parts!

Index of Advertisers

AudioXpress

BAEC, Showcase

Beta Layout

CS Technology, Showcase

DesignSpark chipKIT™ Challenge

Easysync, Showcase

Elnec, Showcase

Eurocircuits

EzPCB/Beijing Draco Electronics Ltd

First Technology Transfer Ltd, Showcase . . .

FlexiPanel Ltd, Showcase

Future Technology Devices, Showcase

Flameg, Showcase

FlexWax Ltd, Showcase

Jackaltac

Labcenter

www.cc-webshop.com 47

http://baec. tripod, com/ 78

www.pcb-pool.com 19,78

www.cstech.co.uk/picdemo 78

www.chipkitchallenge.com 15

www. easysync -ltd. com 78

www.elnec.com 78

www.eurocircuits.com 23

www.v-module.com 31

www.ftt.co.uk 78

www.flexipanel.com 78

www. ftdichip. com 78

www.hameg.com 78

www.hexwax.com 78

www.jackaltac.com 11

www.labcenter.com 88

Maxbotix, Showcase

Microchip

Minty Geek, Showcase

MikroElektronika

Pico Technology

Quasar Electronics

Robot Electronics, Showcase.
Robotiq, Showcase

Schaeffer AG

Showcase

Tyder, Showcase

Virtins Technology, Showcase

www.maxbotix.com 79

www.microchip.com 2

www.mintygeek.com 78

www.easypic7.com 3

www.picoscopemso.com/3114 19

www.guasareiectronics.com 13

www.robot-electronics.co.uk 79

www.robotig.co.uk 79

www.schaeffer-ag.de 19

78, 79

www.tyder.com 79

www. virtins. com 79

Advertising space for the issue 17 January 2012
may be reserved not later than 19 December 2011

with Elektor International Media - Allee 1, 6141 AV Limbricht, the Netherlands
Telephone 0031 (0) 46 4389444 - Fax 0031 (0) 46 4370161 -
e-mail: advertenties@elektor.com to whom all correspondence,
copy instructions and artwork should be addressed.

elektor 12-2011

Personal Download for I © Elektor

87

WITH PRDTEU5 PCB DESIGN

Our completely new manual router makes placing tracks quick and intuitive. During track
placement the route will follow the mouse wherever possible and will intelligently move
around obstacles while obeying the design rules.

All versions of Proteus also include an integrated world class shape based auto-router as
standard.

PROTEUS DESIGN SUITE Features:

■ Hardware Accelerated Performance. ■ Board Autoplacement & Gateswap Optimiser.

■ Unique Thru-View™ Board Transparency. ■ Direct CADCAM, ODB++, IDF & PDF Output.

. Over 35k Schematic & PCB library parts. ■ Integrated 3D Viewer with 3DS and DXF export.

■ Integrated Shape Based Auto-router. ■ Mixed Mode SPICE Simulation Engine.

■ Flexible Design Rule Management. ■ Co-Simulation of PIC, AVR, 8051 and ARM7.

. Polygonal and Split Power Plane Support. ■ Direct Technical Support at no additional cost.

Prices start from just £150 exc. VAT & delivery

Visit our website or
phone 01756 753440
for more details

Labcenter Electronics Ltd. 53-55 Main Street, Grassington, North Yorks. BD23 5AA.
Registered in England 4692454 Tel: +44 (0)1756 753440, Email: info@labcenter.com

Personal Download for I © Elektor