Intelligent sensor design using the microchip dsPIC

303 Pages·2007·5.405 MB·English

by  Huddleston, Creed

Intelligent Sensor Design
Using the Microchip dsPIC®
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Intelligent Sensor Design
Using the Microchip dsPIC®
by Creed Huddleston
AMSTERDAM • BOSTON • HEIDELBERG • LONDON
NEW YORK • OXFORD • PARIS • SAN DIEGO
SAN FRANCISCO • SINGAPORE • SYDNEY • TOKYO
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ISBN-13: 978-0-7506-7755-4
ISBN-10: 0-7506-7755-4
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Printed in the United States of America
Certain materials contained herein are reprinted with the permission of Microchip Technology, Inc.
No further reprints or reproductions may be made of said materials without Microchip Technology Inc.’s
prior written consent.
dsPIC, MPLAB, Microchip, dsPICDEM, and dsPICworks are trademarks or registered trademarks of
Microchip Technology, Inc. “Implementing Intelligent Sensors Using the Microchip dsPIC” is an inde-
pendent book and is not affiliated with, nor has it been authorized, sponsored, or otherwise approved by
Microchip.
This book is lovingly dedicated to my incredible wife Lisa
and my three wonderful children, Kate, Beth, and Dan.
We are truly blessed to be a family, a fact I refl ect upon often.
The book is also dedicated to my sister Sarah, whose tremendous
laugh I’ll always remember and who probably would have been
stunned (but hopefully pleased) to see her name here.
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Contents
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .xi
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xv
About the Author . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xvii
What’s on the CD-ROM? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .xix
Chapter 1: What Are Intelligent Sensors, and
Why Should I Care about Them? . . . . . . . . . . . . . . . . . . . . . . 1
1.1 Conventional Sensors Aren’t Perfect . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.2 First Things First—Digitizing the Sensor Signal . . . . . . . . . . . . . . . . . .7
1.3 Next Step—Add Some Intelligence . . . . . . . . . . . . . . . . . . . . . . . . . . 8
1.4 Finish Up with Quick and Reliable Communications . . . . . . . . . . . . 8
1.5 Put It All Together, and You’ve Got an Intelligent Sensor . . . . . . . . . . 9
1.6 Why Don’t We Make Everything Intelligent? . . . . . . . . . . . . . . . . . . 11
1.7 Real-world Examples of Intelligent Sensors . . . . . . . . . . . . . . . . . . . 13
1.8 Outline of the Remainder of the Book . . . . . . . . . . . . . . . . . . . . . . 16
Chapter 2: Intuitive Digital Signal Processing . . . . . . . . . . . . . 21
2.1 Foundational Concepts for Signal Processing . . . . . . . . . . . . . . . . . . 21
2.2 Issues Related to Signal Sampling . . . . . . . . . . . . . . . . . . . . . . . . . .44
2.3 How to Analyze a Sensor Signal Application . . . . . . . . . . . . . . . . . .47
2.4 A General Sensor Signal-processing Framework . . . . . . . . . . . . . . . .48
2.5 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
Chapter 3: Underneath the Hood of the dsPIC DSC. . . . . . . . . 53
3.1 The dsPIC DSC’s Data Processing Architecture . . . . . . . . . . . . . . . . 55
3.2 Interrupt Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
vii
viii Contents
3.3 The On-chip Peripherals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
3.4 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96
Chapter 4: Learning to be a Good Communicator . . . . . . . . . . 99
4.1 Types of Communications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .99
4.2 Communication Options Available on the dsPIC30F . . . . . . . . . . 106
4.3 High-level Protocols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126
4.4 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .134
Chapter 5: A Basic Toolkit for the dsPIC DSC . . . . . . . . . . . . . 137
5.1 The Application Test Bed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .137
5.2 Overview of the Firmware Framework . . . . . . . . . . . . . . . . . . . . . 138
5.3 Implementation of the Framework Modules . . . . . . . . . . . . . . . . .149
5.4 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 159
Chapter 6: Sensor Application—Temperature Sensor . . . . . . 161
6.1 Types of Temperature Sensors . . . . . . . . . . . . . . . . . . . . . . . . . . . . 162
6.2 Key Aspects of Temperature Measurement . . . . . . . . . . . . . . . . . . . 167
6.3 Application Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185
6.4 Hardware Implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 197
6.5 Firmware Implementation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 200
6.6 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 205
Chapter 7: Sensor Application—Pressure and Load Sensors . . 209
7.1 Types of Load and Pressure Sensors . . . . . . . . . . . . . . . . . . . . . . . . . .209
7.2 Key Aspects of Load Measurement . . . . . . . . . . . . . . . . . . . . . . . . 212
7.3 Application Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 216
7.4 Firmware Implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 219
7.5 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 227
Chapter 8: Sensor Application—Flow Sensors . . . . . . . . . . . . 229
8.1 Types of Flow Sensors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 229
8.2 Key Aspects of Flow Measurement . . . . . . . . . . . . . . . . . . . . . . . . 232
8.3 Application Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 236
8.4 Hardware Implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . .243
8.5 Firmware Implementation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .245
8.6 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 250
Contents ix
Chapter 9: Where Are We Headed? . . . . . . . . . . . . . . . . . . . . 253
9.1 Technology Trends . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 253
9.2 Economic Trends . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 260
9.3 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 261
Appendix A: Software on the Included CD-ROM . . . . . . . . . . 265
A.1 On-disk Website of Resources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .265
A.2 Source Code for the Three Applications . . . . . . . . . . . . . . . . . . . . . . .266
Appendix B: Initialization of the dsPIC DSC
and the System Start-up Code . . . . . . . . . . . . . . . . . . . . . 267
Appendix C: Buffered, Interrupt-driven Serial I/O . . . . . . . . . 271
C.1 Pseudo-code for the Framework . . . . . . . . . . . . . . . . . . . . . . . . . . . .273
C.2 System Initialization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .273
C.3 Reading Data From the Interface . . . . . . . . . . . . . . . . . . . . . . . . . . .273
C.4 Writing Data to the Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .274
Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 275