Table Of ContentAssembly Language using the Raspberry Pi: A Hardware Software
Bridge
Copyright © 2017 by Robert Dunne.
All rights reserved. No part of this book may be reproduced or transmitted in any
form or by any means without the prior written permission of the copyright owner
and publisher. Published in the United States of America by Gaul
Communications, Downers Grove, Illinois.
ISBN 978-0-9701124-1-5 (paperback)
ISBN 978-0-9701124-0-8 (digital)
This book refers to and uses the GNU software and Raspian Linux kernel
distributed for the Raspberry Pi. See the GNU General Public License for details
which is available from the Free Software Foundation, Inc., Boston,
Massachusetts.
Assembly Language Using the Raspberry Pi: A Hardware Software Bridge is an
independent publication and has not been authorized, sponsored, or endorsed by
any of the hardware or software rights holders described herein.
The publisher makes no warranty, express or implied, with respect to the material
contained herein. The program listings, examples, and other information
presented in this book are distributed on an “as is” basis, without warranty.
Although every precaution has been taken in the preparation of this book, neither
the author nor Gaul Communications shall have any liability regarding its use.
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Assembly Language
Using the
Raspberry Pi
A Hardware Software Bridge
Robert Dunne
To
the four ladies in my life
Carol
Shannon
Robyn
Kelly
Contents
Preface
0 Introduction - Computer Basics
1 Compile, Link, Execute
2 Arithmetic Logic Unit
3 Subroutines and ASCII Output
4 True and False
5 Display Numbers in Binary
6 Display Numbers in Hexadecimal
7 Display Numbers in Decimal
8 Data Types and Storage
9 Disassembler
10 Fixed Point
11 Binary Point
12 Floating Point Display
13 Floating Point Coprocessor
14 Precision
15 Performance Using Vectors
16 Text and Logical Input
17 Integer Input
18 Floating Point Input
19 Model View Controller
Epilogue
Appendix A: Raspberry Pi Setup
Appendix B: Binary Numbers
Appendix C: Hexadecimal Numbers
Appendix D: ASCII
Appendix E: Text Editors
Appendix F: ARM Instructions
Appendix G: Vector & Floating Point Instructions
Appendix H: Assembler Directives
Appendix I: Linux Service Calls
Appendix J: GDB Debugger Commands
Appendix K: Command Lines
Appendix L: C Programming
Appendix M: Electronic Interfaces
Appendix N: Thumb Code
Answers to Selected Questions
Preface
H
ow do you use your Raspberry Pi? That’s a question I ask my
students as well as people I meet in the business world. Some use it
for games and entertainment. Some use it as part of a workstation in
a network of computers. Some don’t even use it, but bought one
simply because the price was very reasonable. I primarily use the
Raspberry Pi as part of instruction in electronics and computer
science. Education was the principal motive for the development of
the Raspberry Pi, and you can learn about its creation through the
Raspberry Pi Foundation, a registered charity in the United Kingdom
that promotes computer literacy and enthusiasm.
Assembly language is the computer programming language closest
to a CPU’s (Central Processing Unit) “machine language.” Programs
written in assembly language are unique to a particular CPU design
and are not portable from one CPU manufacturer or model to
another. Programs written in higher level languages like Java,
Python, C++, and Lisp are generally independent of the native
hardware architecture of the CPU on which they will eventually run.
Audience for This Book
This book is part of a lecture and lab course in embedded systems.
Embedded systems are internal computers that control almost
everything today: automobile engines, television sets, furnaces,
vacuum cleaners, cell phones, etc. The objective of this book is to
introduce the novice to both CPU hardware and professional software
development methods by working through sample assembly language
programs. The intended audience is the following:
Anyone wanting to learn assembly language, especially
individuals interested in the Raspberry Pi, the ARM CPU,
VFPv3 floating point coprocessor, and NEON coprocessor
architectures in particular.
Someone who already has assembly language experience, but
now wants to become familiar with the ARM CPU, VFPv3
IEEE 754 floating point processor, and NEON vector
processor resident in the Raspberry Pi.
Electronics engineers who want to bridge the gap toward
software development, and software engineers who want to
bridge the gap toward CPU hardware operation.
College students enrolled in embedded systems and computer
architecture courses.
Expected background for someone reading this book to learn
assembly language using the Raspberry Pi:
Most of my electronics students have no programming
experience. Some have had limited encounters with Basic,
C++, or Java.
Students should be able to start a Raspberry Pi and get it into
Linux command line mode. I have included an appendix that
should be adequate for most people needing some assitance.
Note: Although I refer to the Raspberry Pi, almost any Linux
or Unix system along with GNU utilities for an ARM
processor will be adequate for most of the chapters in this
book.
My embedded systems students have already taken a course
in digital electronics. In other words, they will be familiar
with binary, hexadecimal, ASCII, and hardware concepts like
registers. For those needing assistance or refreshing in these
areas, I have included appendices.
With students having the above background, the approach taken in
this book is to be very thorough in providing detailed programming
examples and not very thorough in explaining binary, hexadecimal,
and ASCII. I have taken this approach based upon several years of
feedback from electronics students of embedded systems indicating
where they want more detail and where they need less. Readers with
a strong background in computer programming may find I develop
coding examples more slowly than they might prefer, and others
might say I didn’t explain binary and hexadecimal adequately
(although I do provide several appendices explaining a variety of
background issues).
Why Did I Write a Book for Learning Assembly Language?
I’ve seen a lot of poorly written programs over the years, and I mean
production code, not just classroom programming. The vast majority
of it comes from people who have learned the elements of a
programming language, but not how to develop software. It’s
comparable to an auto mechanic learning how to use wrenches,
vacuum gauges, and oscilloscopes without knowing how an engine
works. It’s also like a soldier being taught to use a weapon but
without being given the rules of engagement. In this book, I do
introduce the “mechanics” of the ARM CPU and floating point
processor within the Raspberry Pi, but I do it while subtly introducing
software design patterns, object oriented design principles, and
software development life cycles. This book is characterized by the
following:
Independent Study: Although this book is part of my
embedded systems course, it does not rely on additional
material presented in the course. It is expected that the
student will learn assembly language by working through the
examples in this book, and we’ll focus on electronic interfaces
and feedback control methods during class.
Complete examples: Rather than provide just snippets of
code, this book contains complete working programs.
An emphasis on software design methods: Design patterns
and program development life cycles are as important for
assembly language application development as for higher
level language development.
Learn by doing: Prototype programs appear at the beginning
of each chapter to get the readers’ “feet wet” before diving
into the principles to be learned.
Flowcharts: Many students have stated they understand the
concepts better when they can visually see the program flow.
Review questions and exercises: Every chapter ends with a
series of suggested exercises and review questions to
augment the understanding of the material presented.
Answers to some of the review questions are in the back of
the book, but many questions are left unanswered and are
available for classroom assignments.
Why the Raspberry Pi?
So, why did I specifically target this book at the Raspberry Pi when
other development environments have been available to college
students for years?
ARM Processor: The ARM processor is not only a very
interesting CPU architecture, but it is also one of the most
popular CPUs currently in production.
Floating Point Processor: I wanted my embedded systems
students to be both knowledgeable and comfortable with
measured analog data ranging from microvolts to hundreds of
volts. This range of values is best represented in floating point
numbers, and the Raspberry Pi SoC (System on Chip) design
comes standard with a floating point processor. Several
chapters are devoted to programming the VFPv3 and NEON
coprocessors.
Professional Quality: My students are in a curriculum to learn
to produce industrial strength products. The hardware
architecture (ARM CPU) and software (Linux and associated
