Programming the Propeller with Spin. Beginner’s Guide to Parallel Processing

336 Pages·2010·2.633 MB·english

by  harprit Singh Sandhu

Programming the
ProPeller™ with
SPin™: a Beginner’S
guide to Parallel
ProceSSing
harprit Singh Sandhu
Copyright © 2010 by The McGraw-Hill Companies.
ISBN: 978-0-07-171667-3
MHID: 0-07-171667-X
The material in this eBook also appears in the print version of this title: ISBN: 978-0-07-171666-6, MHID: 0-07-171666-1.
contentS
Preface xiii
Part i the Propeller/Spin System 1
Introduction for the Beginner 1
chapter 1 a general introduction to the Propeller chip 3
The Propeller Manual 3
Parallax, Inc. 5
Overall System Description 5
The Propeller Tool 7
Instruments Needed to Support Your Experiments 8
chapter 2 the Propeller chip: an overall description 9
Basic Propeller Specifications 10
Voltage and Amperage Requirements 10
The Operation of the Eight Cogs 10
The Cogs 11
The Hub 12
Forty Pins Total, 32 Pins I/O 12
Connecting to the Propeller 13
The System Counter 14
Program Storage and Execution 14
Objects, Methods, and Other Definitions 15
chapter 3 the hardware Setup 19
Setting Up the Hardware 21
A Fundamental Reality We Have to Consider 23
chapter 4 Software Setup: the “Propeller tool” environment 25
Classroom Analogy 27
Getting Ready to Use the Propeller 28
Installing the Software 28
Our First Program 29
The Typical Spin Program 32
Program Structure 34
General Pin Assignments Used in the Book 36
Propeller FAQ* 38
chapter 5 the Various Propeller memories 43
Assigning Memory for a New Cog 45
A New Cog Can Be Started to Run a Private or Public Method 45
chapter 6 the how and why of Shared memory 47
Memory Usage 48
Variable Validity 49
Loops 50
chapter 7 understanding one cog 51
Static Versus Dynamic 53
One Cog 55
Counters 58
Counter: General Description 59
Assignment of the 32 Bits in Each of the Counters 59
Using Counter A for PWM Generation 60
chapter 8 the eight cogs 65
The Cogs 65
The Flags 66
Special Memory Locations 66
The System Clock 66
Programming 67
The ROM 67
chapter 9 Special terms and ideas 69
The Hardware 69
The Software 70
New Hardware-Related Definitions 70
New Software-Related Definitions 71
chapter 10 the Spin language 75
CON 77
VAR 77
OBJ 78
PUB or PRI 78
Creating a Program with Two Cogs 83
chapter 11 tasks Suited to Parallel Processing 85
Parallel Programming Examples 85
Summary 87
Part ii input and output: the Basic techniques
to Be mastered—learning by doing 89
chapter 12 general discussion of input/output 91
chapter 13 Binary Pulsing 95
chapter 14 Setting up a 16-character-by-2-line
liquid crystal display 101
chapter 15 Binary input and output: reading a Switch
and turning on an led if the Switch is closed 109
Discussion 111
The Repeat Command 112
chapter 16 reading a Potentiometer: creating
an input we can Vary in real time 113
Analog Inputs 114
Advanced Techniques 118
chapter 17 creating and reading Frequencies 129
Creating Audible Frequencies 130
Reading Frequencies 135
chapter 18 reading and creating Pulses 139
Reading Pulse Widths 139
Determining the Pulse Width 140
Pulse Width Creation 146
Part iii the Projects: using what was
learned to Build the Projects 149
chapter 19 Seven-Segment displays: displaying
numbers with Seven-Segment led displays 151
chapter 20 the metronomes 159
chapter 21 understanding a 16-character-by-2-line
lcd display 163
8-Bit Mode 164
Sophisticated Total LCD Control 171
4-Bit Mode 182
chapter 22 running motors: a Preliminary discussion 189
R/C Hobby Servomotors 190
Stepper Motors (Bipolar) 190
Small Brush-Type DC Motors 191
DC Motors with Attached Encoders 191
Relays and Solenoids 191
Small A/C Motors at 120 Volts, Single Phase 192
Understanding the Concept of the
“Response Characteristics” of a Motor 192
So What Does “Compliance” Mean? 192
DC Motor Operation Notes 193
chapter 23 motor amplifiers for Small motors 195
Amplifier Construction Notes (for Homemade Amplifiers) 197
Detailed “Use Information” for the Xavien Two-Axis Amplifier 198
Detailed “Use Information” for the Solarbotics Two-Axis Amplifier 199
chapter 24 controlling r/c hobby Servos 203
Servo Control 204
chapter 25 controlling a Small dc motor 211
The Software 214
chapter 26 running a Stepper motor: Bipolar,
Four-wire motors 225
Stepper Motor Power and Speed 226
Details on Bipolar Motors 226
Running the Motor 227
Programming Considerations 229
The Software 231
chapter 27 gravity Sensor Based auto-leveling table 247
Sensor Specifications 248
Discussion 248
chapter 28 running dc motors with attached
incremental encoders 257
Not about Motors 258
Discussion 258
DC Servo Motors with Encoders 261
Processor Connections 262
The Goal 262
PID Control in Greater Detail 263
Holding the Motor Position 265
Ramping 294
R/C Signal Use 305
Some Advanced Considerations You Should Be Aware Of 312
chapter 29 running Small ac motors: controlling
inductive loads 313
Part iV appendixes 315
appendix a lcdroutines4 and utilities object listings 317
appendix B materials 327
appendix c turning cogs on and off 329
appendix d experiments Board 331
appendix e debugging 335
Debugging and Troubleshooting 335
Dumb Terminal Program 337
Signal Injection Techniques 337
Notes on Solderless Breadboards 338
Debugging at the More Practical Level 339
Writing a Rudimentary Program for Testing the LCD 340
Another List of Simple Checks 341
epilogue 343
index 345
PreFace
After I finished my book Running Small Motors with PIC Microcontrollers, I asked
my friend David H. at HVW Technologies in Canada if he had in any ideas as to what
might be worth covering in my next book. David suggested that a book about the new
Propeller chip from Parallax, written in the same vein as my other hands-on books,
could be a welcome effort. With this in mind, I contacted Parallax, Inc., in California
and they turned me over to Ms. Stephanie Lindsay, their contact person for authors.
Ms. Lindsay was good enough to send me a comprehensive authoring package to get
me started on this adventure. In this book I share what I have learned about the
Propeller chip and parallel processing with you. It is my wish that by the time you
have read through it and have done all the experiments, you will have the confidence,
skills, and knowledge necessary to start using the Propeller chip in ways that will
make your life both more interesting and, hopefully, more productive.
My first reaction to opening the authors’ package and starting on the Propeller
manual was, How am I ever going to learn to use this processor? The material was not
beginner friendly. Although it was at a higher level, it was very interesting. The further
I got into reading and understanding the manual, the more fascinated I became with
what the very clever engineers at Parallax had created. It is certainly one of the won-
ders of the modern world that you can buy eight 32-bit processors and shared memory
for less than $8. In this book we will discover what all this, including parallel process-
ing, means to us as engineers, technicians, and hobbyists. As always, I will minimize
the use of complicated formulas and jargon so that if you are interested in things
mechanical and electronic and have a rudimentary knowledge of what a computer
program is, you will be able to use these processors to undertake simple tasks and
maybe even some fairly complicated projects in a parallel-processing environment.
There are, of course, two aspects to learning how to use the Propeller chip. The first
is learning how to use each of the identical 32-bit processors in the chip. Parallax calls
each of these eight processors a “cog,” and each of these cogs is similar to a typical
32-bit processor, with some special features added and some left off. The second is
learning how to make these eight cogs interact with one another in an effective way
to explore the fascinating parallel-processing possibilities that are now suddenly
within our reach. Because the eight 32-bit processors on the chip are identical, once
you have learned to use one of them, you have learned to use all of them.
The intellectual discipline that has to be mastered involves setting up the problem
in such a way that the eight processors can be used in the most effective way possible,
thus creating a viable solution for the task you have in mind. This has to do with
really understanding the problem and with learning how to break a problem down into
separate tasks, each of which can be assigned to one of the cogs, in an orderly and
logical way. We will learn how to do this.
Because not every problem lends itself to a parallel-processing solution, we will
spend some time on learning how to identify those problems that can be solved
within a parallel-processing environment.
This book is intended for the novice user. It is for the novice user for two reasons:
One, the material that Parallax provides regarding this chip is more advanced than a
first-time user can master with ease. Two, I am also a novice as far as this particular
discipline (parallel processing) goes. In this book, I share what I have learned with
you, in a straightforward and hopefully nonintimidating manner that you will find use-
ful. We will learn by doing, which is the best way to learn to do anything. Before we
can start, though, we have to understand what the system is capable of and how this
book is organized to address the tasks at hand.
This book is divided into four parts that compartmentalize what we are interested in:
■ The first part of the book introduces you to the Propeller chip, starting with one cog
(the term used by Parallax for each of the eight 32-bit processors in the Propeller
chip). First, we learn about just one of the eight processors and how to interact with
the I/O provided on the chip. This I/O is in a shared portion of the chip that all the
cogs can address. All the features of the one cog are covered in detail. At the end
of the first part, you should have a good idea of what the system is all about and be
ready to begin using it.
■ In the second part of the book, I cover what you need to know to develop the skills
necessary for creating a system that allows the cogs to work together. We will do
this by learning how to make the Propeller interact with a number of input and
output devices. I have selected the kind of devices an amateur enthusiast, a techni-
cian, or an engineer is likely to be interested in interacting with on a day-to-day
basis—displays, switches, detectors, motors, and such. The limited memory in the
system does not lend itself to the handling of large arrays and related number-
crunching applications, so simple control applications like the ones we will con-
sider are the most suited for investigation by us beginners. The major objective of
this part of the book is to learn how to read and create signals of various types.
■ In the third part of the book, we use the lessons we have learned in Part II to build
and program a number of devices using the Propeller chip. The device in each
experiment is a real-world application of the parallel-processing environment, and
each one uses more than one cog. Not all the projects are completed 100 percent,
so you have the challenge to complete them. Appropriate information and hints are
provided.
■ The fourth part of the book is composed of appendixes that provide you with sup-
plemental information you will find helpful in using the device. This includes the
hardware and software resources needed for the experiments we undertake. Where
special items are needed, I have made arrangements to provide them on my website
at Encodergeek.com.
A large part of the information you need to help you use this processor can be found
on websites maintained by Parallax and others. I recommend that you get familiar with
what is in these websites and get comfortable with using the material these websites
provide. The discussion forums are extraordinarily useful and should be made a part
of your regular reading and learning experience. The following three online resources
provide a good starting point as you progress through this book:
■ The Parallax forums. These forums are your most useful resource.
■ Wikipedia provides useful general information.
■ The support web pages provide specific information.
The Propeller chip software is organized such that routines called methods and
procedures, created by one person, can be used by others with relative ease. Most of
these procedures are well documented, and because all the code is visible, you can
modify it to serve your more specific needs should that become necessary. This being
the case, becoming familiar with and studying the work done by others is one of the
skills you need to develop. I will provide methods with full documentation to support
the devices we use so that you can see how these methods are created and then called
in subsequent programs.
All the experiments in this book can be undertaken with the Propeller Education
Kit (32305) provided by Parallax and a minimal amount of additional hardware.
Other than the Propeller programming tools provided by Parallax at no charge, con-
sisting of Spin (a high-level language) and PASM (the Propeller Assembly language),
no other software is needed. The few extra hardware items needed are listed in
Appendix B. The work that we will undertake will be designed around the creation
of software for running the type of devices you might use in the design of day-to-day
projects on the hobby bench, the engineering laboratory, or the industrial research
facility. The devices selected are inexpensive and fit within the constraint of working
well with beginners who are just learning how to use the Propeller chip. None are
hard to use.
As mentioned previously, Parallax provides two languages for programming the
Propeller chip. The first language is a high-level language called Spin. The Spin lan-
guage can be used for almost everything we need to do, except for tasks that need
extreme speed and therefore have to be handled with some sort of Assembly language
constructs. All the work in this book will be done in the Spin language, with minor
calls to Assembly language routines if and when necessary. The goal is to become
familiar with the Spin language and to be aware of the capabilities that Assembly
language provides. Assembly language routines can be embedded in the Spin lan-
guage programs with minimal effort. In that this book addresses the needs of begin-
ners, we will not do any programming in the Assembly language PASM.
A large part of this book is dedicated to getting an understanding of how the Spin
language is used to manage an eight-processor system and its shared memory. A
number of simple rules are formulated to allow you to do this from a beginner’s point
of view. Starting and stopping cogs and assigning specific tasks to them is covered to
give you a feel for how you might use these functions. Because there are only eight
cogs on the chip, we have to have some discipline regarding how they are to be used.
Because each cog is also capable of performing more than one task, as is any “run of
the mill” processor, we also need some understanding of when and why more than one
task should be assigned to one processor. This, too, is discussed so that you can assign
tasks in a more logical manner when you design the hardware and software for your
projects.
The Spin language does not support an interrupt capability of any description.
Having eight processors in a parallel configuration pretty much eliminates the need for
interrupts. However, there are still times when you may need to assign some form of
more immediate attention to a task, and techniques that can be used to achieve this are
demonstrated.
Attention is also given to the special features each cog supports. Of advanced
interest is the use of the two counters provided in each cog and the interesting ways
in which they can be used. The use of these counters is not obvious to the first-time
user, especially so if he is a beginner. These counters provide an important and
powerful function within each cog, and using them effectively is an important part
of using the Propeller chip. Because there is a total of 16 of these counters in the
Propeller, they provide a resource we cannot ignore if we are to consider ourselves
as being familiar with the Propeller system. Parallax provides detailed information
on using these counters, but most of it is beyond the understanding of beginners.
We will use a counter to create a PWM signal when we need one; no other use is
covered.
Part III of the book is devoted to the projects. I have concentrated on controlling the
types of things beginners will be interested in. I have covered some of these tasks in
other books I have written, and other authors have written a lot about these topics as
well. The difference in this resource is that we concentrate on how to undertake these
tasks with the Propeller chip and its parallel-processing environment in a way that’s
interesting to the beginning programmer. Controlling things also has a lot do with
process control, so in a way this book is a simplified introduction to process control
in the parallel environment.
The one thing that the Propeller chip does not do well is handle large amounts of
data simultaneously. Such data crunching requires three basic resources:
■ A fast processor to perform the work quickly. (This we have.)
■ The implementation of a standardized, verified math package in the software to
allow for sophisticated mathematical manipulations.
■ A large amount of memory to store all the data to be crunched.
The Propeller chip does not support all three of these capabilities and implemen-
tations. This does not mean that we cannot do the day-to-day math we need for our
control operations; however, it does means that we are not working with a machine
designed for crunching large number arrays. Consequently, there is no discussion
of problems that require sophisticated mathematical capabilities in this resource.