Bruce Smith - Raspberry Pi Assembly Language RISC OS Beginners (Hands On Guide)

Raspberry Pi Assembly Language RISC OS Beginners

Raspberry Pi

Assembly Language RISC OS Beginners

Hands On Guide

Bruce Smith

ISBN-13: 978-0-9923916-3-8

First edition: February 2014 [0001]

Editor: Alan Ford Edits

Cover: Sumit Shringi, Graphic Designer (Book Cover-Design)

Typeset in 11 on l2pt Garamond by BSB using Serif PagePlus x6

All Trademarks and Registered Trademarks are hereby acknowledged.

Within this Hands On Guide the term BBC refers to the British Broadcasting Corporation. Raspberry Pi and the Raspberry Pi logos are registered trademarks of the Raspberry Pi Foundation.

Raspberry Pi Assembly Language: RISC OS Beginners Hands On Guide is not endorsed by the Raspberry Pi Foundation.

All rights reserved. No part of this book (except brief passages quoted for critical purposes) or any of the computer programs to which it relates may be reproduced or translated in any form, by any means mechanical electronic or otherwise without the prior written consent of the copyright holder.

Disclaimer: Whilst every effort has been made to ensure that the information in this publication (and any programs and software) is correct and accurate, the author and publisher can accept no liability for any consequential loss or damage, however caused, arising as a result of the information printed in this book and on any associated websites. Because neither BSB nor the author have any control over the way in which the contents of this book is used, no warranty is given or should be implied as to the suitability of the advice or programs for any given application. No liability can be accepted for any consequential loss or damage, however caused, arising as a result of using the programs or advice printed in this book.

Published by BSB www.brucesmith.info.

About the Author

Bruce Smith purchased his first computer an Acorn Atom in 1980. He was immediately hooked, becoming a regular contributor to the mainstream computer press including Computing Today and Personal Computer World. With the arrival of the BBC Micro his magazine work expanded into books and his 1982 title Interfacing Projects for the BBC Micro (published by Addison Wesley) has become regarded as a classic of the time as the first book showing home users how to connect the computer to the outside world. He was one of the first to write about the ARM chip when it was released on the Acorn Archimedes in 1987.

Well over 100 books later Bruce has written about all aspects of computer use. His friendly, lucid style of writing caused one reviewer to write, This is the first computer book I have read in bed for pleasure rather than to cure insomnia! Bruces books have been translated into many languages and sold across the world.

Bruce also writes about sport and his publishers have included BBC Books, Virgin Books, Rough Guides, Headline and Mainstream Publishing. He has been a regular contributor for BBC local and national radio and has appeared on Channel 4s The Big Breakfast and BBC World Service.

Follow Bruce on Twitter: @brucefsmith

www.brucesmith.info

Preface

This original edition of this book was published under the title Raspberry Pi Assembly Language Beginners. The original title seemed to create confusion as to which operating system it dealt with, especially after the launch of Raspberry Pi Assembly Language RASPBIAN Beginners, which was an introduction to the ARM using GCC on the Raspbian operating system and its various Linux incarnations.

I thought it was a good time to substantially revise and update the original text and take the opportunity to rename the booksince it well over a year oldto make it clear where its sits in Raspberry Pi distro hierarchy. This new release contains several new chapters that deal specifically with features supplied by the Raspberry Pi system-on-chip structure and expansion ports. This includes a look at the Floating Point co-processors and how to program the GPIO port.

It should be acknowledged that there are many ways to archive a particular outcome when programming in assembly language and especially within the RISC OS environment. I am rather old school in my approach to these matters and more of a traditionalist to the original RISC OS concepts.

The revision of this volume goes hand-in-hand with the release of Raspberry Pi RISC OS System Programming Revealed which could be considered a companion volume, especially if you wish to delve further into the working and operations of RISC OS . Note that a couple of chapters overlap between the two book, so please check the website at www.brucesmith.info if you are looking for specific information so as to ensure you do not double up.

Bruce Smith, Sydney, January 2014

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1: Introduction

It didnt surprise me when, early in 2013, it was announced that the Raspberry Pi had sold one million units. And counting... It took me back more years decades even than I care to remember when it was announced that the BBC Micro had done the same. Both came out of businesses based in Cambridge in the UK and there were even more links between the two than you might imagine.

Both systems fascinated me and literally millions of other people. The first system took every last penny of my savings at the time, but the Raspberry Pi didnt even drain the cash in my wallet. But while the ticket price for each was vastly different, pretty much everything else about them was so familiar. Not least their ability to run a wide range of software and educational tools and how easy it was to connect external devices and control the outside world. I would suspect that most people who own one Raspberry Pi, actually own several.

For the first time since the BBC Micro there is an affordable and infinitely accessible system that just about anyone can use. Meanwhile, the PC and Mac have dominated the market and other more games-orientated boxes have been available. But none of these have impacted the technical home hobbyist user. The techsperts have had a variety of development boards to experiment and fiddle with, again mostly beyond the scope of the home hobbyist computer market. For the cost of a couple of music albums or new release DVD, the Raspberry Pi has changed all that. I wonder if the Raspberry Pi could be classed as the worlds first disposable computer?

Imagination Unlimited

One reason for the birth of the Raspberry Pi was to make it easy for people to take up programming, with the aid of a competitively priced computer system whose use was limited only by the users imagination. I hope this book will help many of you reading it realise that dream. In fact, it isn't a dream. It is a probability if you continue your way through the pages that follow a first step on a rewarding and educational pastime. And, who knows, you may become part of a new generation of computer programmers working at the sharp end of what is possible.

This book provides an introductory tutorial in writing assembly language on the Raspberry Pi and specifically using RISC OS. Assembly language generates machine code that can be run directly on your computer. I first learned to program assembly language on the Acorn Atom (the BBC Micros predecessor) and then on its successor (the Archimedes) the assembly language now used on the Raspberry Pi. If anything that proves that what you learn here should stand you in good step for many years to come. So it is a significant investment.

Start Experimenting

While this is not a book for the complete novice, you certainly do not require any experience with assembly language or machine code to be able to pick it up and start reading and experimenting. Programming experience would be beneficial and any structured language will have provided the groundwork for many of the fundamental concepts required.