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Keil Microcontroller Development Tools help you create embedded applications quickly and accurately.. 4 Issue 202 May 2007 CIRCUIT CELLAR ® www.circuitcellar.comFOUNDER/EDITORIAL DIRECTO

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CIRCUIT

T H E M A G A Z I N E F O R C O M P U T E R A P P L I C AT I O N S

$4.95 U.S ($5.95 Canada)

MEASUREMENT & SENSORS

Magnetometer Design

Portable

Temperature Meter

Energy Analyzer

Self-Recording

Camera

#202 May 2007

GET STARTED WITH CAPSENSE NOW

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Download free PSoC Express ™ visual embedded software:

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Register for a CapSense NetSeminar:

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PSoC®-based Capacitive Touch Sensing

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replaces buttons, switches, sliders and other mechanical

inputs in your product CapSense enables:

Fast changes to your design at any stage from concept

through production CapSense is not a fixed-function ASIC

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Single-chip implementation supporting multiple interfaces –

buttons, sliders, touch screens, touchpads and proximity

detectors – on a variety of conductive substrates.

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CapSense.

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Link Instruments

17A Daniel Road East · Fairfield, NJ 07004 · Fax (973) 808-8786

www.Linkins4.com

Link Instruments (973) 808-8990

PC-Based Test Equipment

• 2 Channel Digital Oscilloscope

• 500 MSa/s max single shot rate

• 1Mpt sample memory

250 MSa/S (Dual channel) 512 Kpts

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• $950 (DSO, Probes, Software & power supply)

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• 40 to 160 channels

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• 16 Level Triggering

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• USB 2.0 and Parallel Interface

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LA5240 (200MHz, 40CH) $1700

LA5280 (200MHz, 80CH) $2350

LA5540 (500MHz, 40CH) $2500

LA5580 (500MHz, 80CH) $3500 LA55160 (500MHz, 160CH) $7500

Digital Oscilloscopes

NEW!

www.keil.com 800-348-8051

Only 4 Steps

are required to generate efficient, reliable

applications with the μVision IDE and

development tools from Keil.

Step 1 Select Microcontroller and

Specify Target Hardware

Use the Keil Device Database ( ) to find the

optimum microcontroller for your application

In Vision, select the microcontroller to pre-configure tools and

obtain CPU startup code

www.keil.com/dd

μ

Step 2 Configure the Device and

Create Application Code

The μVision Configuration Wizard helps you tailor startup code

to match your target hardware and application requirements

Extensive program examples and project templates help you

jump-start your designs

Step 3 Verify Program Execution with

Device Simulation

High-speed simulation enables testing

before hardware is available and helps you

with features like instruction trace, code

coverage, and logic analysis

Step 4 Download to Flash and

Test Application

Once your application is runs

in simulation, use the Keil

ULINK USB-JTAG Adapter for

Flash programming and final

application testing

Keil Microcontroller Development Tools

help you create embedded applications quickly and accurately Keil tools are easy to learn and use, yet powerful enough for the most

demanding microcontroller projects.

Components of Keil Microcontroller Development Kits

Keil makes C compilers, macro assemblers, real-time kernels, debuggers, simulators, evaluation boards, and emulators.

Over 1,200 MCU devices are supported for:

- 8051 and extended 8051 variants

- C166, XC166, and ST10

- ARM7, ARM9, and Cortex-M3 Download an evaluation version from

n n n

8-bit 16-bit 32-bit

www.keil.com/demo

4 Issue 202 May 2007 CIRCUIT CELLAR ® www.circuitcellar.com

FOUNDER/EDITORIAL DIRECTOR

Steve Ciarcia

MANAGING EDITOR

C.J Abate

WEST COAST EDITOR

Tom Cantrell

CONTRIBUTING EDITORS

Jeff Bachiochi Ingo Cyliax George Martin

Ed Nisley

NEW PRODUCTS EDITOR

John Gorsky

PROJECT EDITORS

Steve Bedford Ken Davidson David Tweed

ASSOCIATE EDITOR

Jesse Smolin

ADVERTISING

860.875.2199 • Fax: 860.871.0411 • www.circuitcellar.com/advertise

PUBLISHER

Sean Donnelly Direct: 860.872.3064, Cell: 860.930.4326, E-mail: sean@circuitcellar.com

ADVERTISING REPRESENTATIVE

Shannon Barraclough Direct: 860.872.3064, E-mail: shannon@circuitcellar.com

ADVERTISING COORDINATOR

Valerie Luster E-mail: val.luster@circuitcellar.com

CONTACTS

SUBSCRIPTIONS

Information: www.circuitcellar.com/subscribe, E-mail: subscribe@circuitcellar.com Subscribe: 800.269.6301, www.circuitcellar.com/subscribe, Circuit Cellar Subscriptions, P.O Box 5650,

Hanover, NH 03755-5650

Address Changes/Problems: E-mail: subscribe@circuitcellar.com

GENERAL INFORMATION

860.875.2199, Fax: 860.871.0411, E-mail: info@circuitcellar.com

Editorial Office: Editor, Circuit Cellar, 4 Park St., Vernon, CT 06066, E-mail: editor@circuitcellar.com New Products: New Products, Circuit Cellar, 4 Park St., Vernon, CT 06066, E-mail: newproducts@circuitcellar.com

AUTHORIZED REPRINTS INFORMATION

860.875.2199, E-mail: reprints@circuitcellar.com

AUTHORS

Authors’ e-mail addresses (when available) are included at the end of each article.

CIRCUIT CELLAR®, THE MAGAZINE FOR COMPUTER APPLICATIONS (ISSN 1528-0608) is published monthly by Circuit Cellar

Incorporated, 4 Park Street, Vernon, CT 06066 Periodical rates paid at Vernon, CT and additional offices One-year (12 issues)

subscription rate USA and possessions $23.95, Canada/Mexico $34.95, all other countries $49.95.Two-year (24 issues) sub-scription rate USA and possessions $43.95, Canada/Mexico $59.95, all other countries $85 All subsub-scription orders payable in

U.S funds only via Visa, MasterCard, international postal money order, or check drawn on U.S bank Direct subscription orders

and subscription-related questions to Circuit Cellar Subscriptions, P.O Box 5650, Hanover, NH 03755-5650 or call 800.269.6301.

Postmaster: Send address changes to Circuit Cellar, Circulation Dept., P.O Box 5650, Hanover, NH 03755-5650.

Circuit Cellar® makes no warranties and assumes no responsibility or liability of any kind for errors in these programs or schematics or for the consequences of any such errors Furthermore, because of possible variation in the quality and condition of materials and workmanship of read-er-assembled projects, Circuit Cellar® disclaims any responsibility for the safe and proper function of readread-er-assembled projects based upon or from plans, descriptions, or information published by Circuit Cellar®.

The information provided by Circuit Cellar® is for educational purposes Circuit Cellar® makes no claims or warrants that readers have a right to build things based upon these ideas under patent or other relevant intellectual property law in their jurisdiction, or that readers have a right to construct or operate any of the devices described herein under the relevant patent or other intellectual property law of the reader’s jurisdiction The reader assumes any risk of infringement liability for constructing or operating such devices.

Entire contents copyright © 2007 by Circuit Cellar, Incorporated All rights reserved Circuit Cellar is a registered trademark of Circuit Cellar, Inc Reproduction of this publication in whole or in part without written consent from Circuit Cellar Inc is prohibited.

CHIEF FINANCIAL OFFICER

Jeannette Ciarcia

MEDIA CONSULTANT

Dan Rodrigues

CUSTOMER SERVICE

Debbie Lavoie

CONTROLLER

Jeff Yanco

ART DIRECTOR

KC Prescott

GRAPHIC DESIGNER

Mary (Turek) Sobuta

STAFF ENGINEER

John Gorsky

Cover photography by Chris Rakoczy—Rakoczy Photography

www.rakoczyphoto.com

PRINTED IN THE UNITED STATES

TASK MANAGER

First, your name and project appear in Circuit Cellar magazine

Then, your name and a description of your project appear on our

recently revamped web site (www.circuitcellar.com) Next, you start

getting noticed by our subscribers and advertisers Soon thereafter,

Dave Tweed adds your name to his well-known online Circuit Cellar

archive (www.dtweed.com/circuitcellar/authors.htm) Around the same

time, professors from all over the world who take part in our College

Subscription Program (http://www.circuitcellar.com/subscriptions/

college.html) instruct their students to download your article At that

point, your name and project are in the “network” and they start

get-ting picked up by the search engines And just like that, you have

max-imum exposure

Each month, I get dozens of proposals from engineers who are

interested in publishing articles in the embedded design community’s

favorite magazine Although the engineers come from different

back-grounds, countries, and generations, they are all looking for the same

thing: exposure And which publication is better than Circuit Cellar at

shining the light on the world’s best embedded designs? There isn’t

one

The “Measurement & Sensors” issue is always in high demand

Each year, we feature articles about the year’s best

microcontroller-based systems that are used for taking measurements, accumulating

data, and sensing a variety of stimuli In this issue, we have great

arti-cles about projects that are sure to keep you thinking about new

designs well into 2008 The tradition continues

James Koehler kicks things off with a great article about a proton

precession magnetometer that he developed for anyone interested in

archaeological research and geophysical exploration (p 14) This

arti-cle is more than a great introduction to magnetometer technology; it’s

a step-by-step guide to building custom sensors

As an instrumentation engineer in the Chemistry department at

Dalhousie University in Canada, Brian Millier works with measurement

systems every day In “Temperature Calibration System,” he walks you

through the process of designing and building a handy portable

tem-perature meter (p 32) Brian describes everything from calibrating

sensors and thermocouples to measuring platinum RTDs

Need an energy and load analyzer on your workbench or in the

lab? Ronaldo Duarte’s cost-effective, M16C/62P-based data logger is

the perfect system for measuring RMS voltage, current, power,

har-monics, and frequency (p 58) You don’t need to shell out big bucks for

a commercial system Just follow Ronaldo’s lead and build your own

Well, the genie is out of the bottle For more than 19 years, the

world’s top embedded designers and programmers have been using

Circuit Cellar to showcase their projects and demonstrate their talent

Why shouldn’t you? Whether you are looking to take your product to

market, impress potential employers, or simply show off your design

skills, Circuit Cellar can give you the exposure you need

Drop me a line if you think you have what it takes to join the elite

list of published Circuit Cellar authors I’d love to hear from you

Maximum Exposure

cj@circuitcellar.com

6 Issue 202 May 2007 CIRCUIT CELLAR ® www.circuitcellar.com

May 2007: Measurement & Sensors

4 TASK MANAGER

Maximum Exposure C.J Abate

8 NEW PRODUCT NEWS

edited by John Gorsky

93 CROSSWORD

FEATURES

DEPARTMENTS

94 INDEX OF ADVERTISERS

June Preview

96 PRIORITY INTERRUPT

Keeping the Lights On Steve Ciarcia

67 LESSONS FROM THE TRENCHES

More “Hello World”

C Program Flow George Martin

72 FROM THE BENCH

What’s the Slope?

Use an Accelerometer to Measure Slope Jeff Bachiochi

78 SILICON UPDATE

Be All You Can Bee

Tom Cantrell

14 Proton Precession Magnetometer

James Koehler

24 Circuit Board Plotting

Curt Carpenter

32 Temperature Calibration System

Brian Millier

43 Embedded USB Host

Lane Hauck

COLUMNS

What’s o Circuit

48 The Witness Camera

Build a Self-Recording Surveillance Camera Alberto Ricci Bitti

Grand Prize Atmel AVR Design Contest 2006

58 Energy and Load Analyzer

Ronaldo Duarte

Innovative Sensor Setup (p 14) Temperature Meter (p 32)

Compact Self-Recording Camera (p 48)

Measure Slope (p 72)

Dream of Darkness,

Wasteman!

What can AVR picoPower

do for your design?

• True 1.8V supply voltage enabling operation of all features and core down to 1.8V

• Minimized leakage current enabling 100 nA Power Down sleep consumption

• Sleeping brown-out detector enabling full protection with no power penalty

• Ultra low power 32 kHz crystal oscillator enabling operation at only 650 nA

8 Issue 202 May 2007 CIRCUIT CELLAR ® www.circuitcellar.com

1-WIRE TEMPERATURE SENSOR WITH LOCATION DETERMINATION

The DS28EA00 is a 1-Wire digital temperature sensor with ±0.5°C

accuracy and a new Chain mode signaling and protocol feature that

quickly and automatically determines the physical location of

individ-ual sensors in an environment where multiple sensors are connected to

a common 1-Wire line The DS28EA00 is ideal for applications that

require accurate multipoint digital temperature measurements with

minimal wiring complexity and cost

The first of its kind to be able to determine the physical location of

multiple temperature sensors, the DS28EA00 includes a Chain mode

command set and two signal pins for daisy-chaining multidropped

devices A 1-Wire host controller then uses the Chain mode command

protocol to learn the 64-bit serial number of each part in the chain,

starting with the first device on the line and proceeding sequentially

This sequence knowledge is directly linked to the physical location of

the DS28EA00 in the system Additionally, the two Chain mode

daisy-chain signal pins are dual-purpose: they can be used to detect the

physi-cal location of a device in a network, or they can be used as a 5-V/4-mA

GPIO to control LED indicators or other I/O signaling

The temperature

sensor is available

in an eight-pin

microSOP package

Prices start at $2.27

for quantities of

1,000 and up

Maxim Integrated

Products, Inc.

www.maxim-ic.com

STEPPER CONTROLLER WITH USB INTERFACE

The HS-20USB is a four-axis step motor controller with a USB

inter-face Designed for use with external-step as well as direction, full, or

half-step drives, such as the CY-41, the HS-20USB includes encoder

sup-port for each of the four axes and an embedded interpreter for CyberVec,

CyberPak’s powerful and comprehensive step motor-system control

lan-guage Auxiliary digital and analog I/O, which can be configured for

joy-stick and control panel interface support and an auxiliary RS-232

inter-face, which can be used in place of the USB port and as a multidrop link

to as many as 15 additional HS-20USB systems, are also included

The HS-20USB can operate under the direct control of a host PC by

executing CyberVec commands transmitted via the USB port, or it can

operate alone by executing a previously downloaded CyberVec program

stored in its internal flash memory The USB interface operates in

RS-232 Emulation mode and includes host PC software that provides a “virtual” COM port addressable by any legacy application The HS-20USB

costs $499 for quantities of

100

CyberPak Company, Inc.

www.cyberpakco.com

NEW ZX MICROCONTROLLER

The ZX-1281 is a 64-pin TQFP

micro-controller targeted at high-volume products and resource-intensive applications where additional I/O capabilities are required All ZX-series microcontrollers are programmed

in ZBasic, a subset of Microsoft Visual Basic (VB6), with microcontroller-specific extensions and other productivity enhance-ments

The newest member of the ZX micro-controller family is based on Atmel’s ATmega1281 microcontroller The primary benefits offered by the ZX-1281 are increased execution speed, expanded user RAM (a standard of 7.5 KB and a maximum

of 63 KB), extended user program space (a total of 60 KB), additional PWM channels (up to six), and a second hardware serial port The new ZX-1281 is largely source-code-compatible with the previously released ZX family

The ZBasic programming language is a subset of Visual Basic (VB6) with exten-sions suitable for microcontroller program-ming The ZBasic compiler can detect common programming defects, such as the use of a variable before its initialization and other likely errors The compiler incor-porates advanced optimization techniques that help programmers pack more func-tionality into the available code and data spaces, such as eliminating unused or superfluous variables and unreachable code

The ZX-1281 costs $49.95 for a single

unit Volume pricing is available You can also purchase a ZX-1281 development board to facilitate the quick prototyping of

a ZX-1281 application The development board, which includes a ZX-1281, costs

$79.95.

Elba Corp.

www.zbasic.net