Raspberry Pi Raspberry Pi User Manual
www.allitebooks.com
Raspberry Pi®
User Guide
Eben Upton and Gareth Halfacree
A John Wiley and Sons, Ltd., Publication
www.allitebooks.com
Raspberry Pi®
User Guide
www.allitebooks.com
is edition rst published 2012
© 2012 Eben Upton and Gareth Halfacree
Registered oce
John Wiley & Sons Ltd., e Atrium, Southern Gate, Chichester, West Sussex, PO19 8SQ, United Kingdom
For details of our global editorial oces, for customer services and for information about how to apply for permission to
reuse the copyright material in this book please see our website at www.wiley.com.
e right of the authors to be identied as the authors of this work has been asserted in accordance with the Copyright,
Designs and Patents Act 1988.
All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form
or by any means, electronic, mechanical, photocopying, recording or otherwise, except as permitted by the UK Copyright,
Designs and Patents Act 1988, without the prior permission of the publisher.
Wiley also publishes its books in a variety of electronic formats. Some content that appears in print may not be available in
electronic books.
Designations used by companies to distinguish their products are often claimed as trademarks. All brand names and product names used in this book are trade names, service marks, trademarks or registered trademarks of their respective owners. e publisher is not associated with any product or vendor mentioned in this book. is publication is designed to
provide accurate and authoritative information in regard to the subject matter covered. It is sold on the understanding that
the publisher is not engaged in rendering professional services. If professional advice or other expert assistance is required,
the services of a competent professional should be sought.
Trademarks: Wiley and the Wiley logo are trademarks or registered trademarks of John Wiley and Sons, Ltd. and/or its
aliates in the United States and/or other countries, and may not be used without written permission. Raspberry Pi and
the Raspberry Pi logo are registered trademarks of the Raspberry Pi Foundation. All other trademarks are the property of
their respective owners. John Wiley & Sons, Ltd. is not associated with any product or vendor mentioned in the book.
Google Drive™ is a registered trademark of Google™.
A catalogue record for this book is available from the British Library.
ISBN 978-1-118-46446-5 (pbk); ISBN 978-1-118-46448-9 (ebk); ISBN 978-1-118-46447-2 (ebk); ISBN 978-1-118-46449-6 (ebk)
Set in 10 pt. Chaparral Pro by Indianapolis Composition Services
Printed simultaneously in Great Britain and the United States
www.allitebooks.com
Publisher’s Acknowledgements
Some of the people who helped bring this book to market include the following:
Editorial and Production
VP Consumer and Technology Publishing
Director
Michelle Leete
Associate Director–Book Content
Management
Martin Tribe
Associate Publisher
Chris Webb
Executive Commissioning Editor
Craig Smith
Assistant Editor
Ellie Scott
Project Editor
Kathryn Duggan
Copy Editor
Kathryn Duggan
Marketing
Associate Marketing Director
Louise Breinholt
Marketing Manager
Lorna Mein
Senior Marketing Executive
Kate Parrett
Composition Services
Compositor
Erin Zeltner
Proofreader
Wordsmith Editorial
Indexer
BIM Indexing & Proofreading Services
Technical Editor
Omer Kilic
Editorial Manager
Jodi Jensen
Senior Project Editor
Sara Shlaer
Editorial Assistant
Leslie Saxman
www.allitebooks.com
www.allitebooks.com
About the Authors
Eben Upton is a founder and trustee of the Raspberry Pi Foundation, and serves as its
Executive Director. He is responsible for the overall software and hardware architecture of
the Raspberry Pi, and for the Foundation's relationships with its key suppliers and customers.
In an earlier life, he founded two successful mobile games and middleware companies,
Ideaworks 3d Ltd. and Podfun Ltd., and held the post of Director of Studies for Computer
Science at St John's College, Cambridge. He holds a BA, a PhD and an MBA from the
University of Cambridge.
In his day job, Eben works for Broadcom as an ASIC architect and general troublemaker.
Gareth Halfacree is a freelance technology journalist and the co-author of the Raspberry Pi
User Guide alongside project co-founder Eben Upton. Formerly a system administrator
working in the education sector, Gareth’s passion for open source projects has followed him
from one career to another, and he can often be seen reviewing, documenting or even
contributing to projects including GNU/Linux, LibreOce, Fritzing and Arduino. He is also
the creator of the Sleepduino and Burnduino open hardware projects, which extend the
capabilities of the Arduino electronics prototyping system. A summary of his current work
can be found at http://freelance.halfacree.co.uk.
www.allitebooks.com
For Liz, who made it all possible.
—Eben
For my father, the enthusiastic past,
and my daughter, the exciting future.
—Gareth
www.allitebooks.com
Table of Contents
Introduction ......................................... 1
Programming is fun! ..........................................................1
A bit of history ...............................................................3
So what can you do with the Raspberry Pi? ......................................8
Part I: Connecting the Board
CHAPTER 1
Meet the Raspberry Pi ................................. 11
ARM vs. x86 ................................................................12
Windows vs. Linux ..........................................................13
Getting Started with the Raspberry Pi ..........................................14
Connecting a Display .....................................................14
Composite Video ......................................................14
HDMI Video ..........................................................15
DSI Video .............................................................16
Connecting Audio ........................................................16
Connecting a Keyboard and Mouse .........................................17
Flashing the SD Card ......................................................19
Flashing from Linux ....................................................20
Flashing from OS X ....................................................21
Flashing from Windows ................................................21
Connecting External Storage ...............................................22
Connecting the Network ..................................................23
Wired Networking .....................................................24
Wireless Networking ...................................................25
Connecting Power ........................................................26
CHAPTER 2
Linux System Administration ............................ 27
Linux: An Overview .........................................................28
Linux Basics ................................................................30
Introducing Debian ..........................................................30
Using External Storage Devices ...............................................34
Creating a New User Account .................................................36
File System Layout ..........................................................37
Logical Layout ...........................................................37
Physical Layout ..........................................................39
Installing and Uninstalling Software ...........................................40
Finding Software .........................................................41
Installing Software ........................................................42
Uninstalling Software .....................................................43
Upgrading Software .......................................................44
www.allitebooks.com
xii
RASPBERRY PI USER GUIDE
CHAPTER 3
Troubleshooting..................................... 45
Keyboard and Mouse Diagnostics .............................................46
Power Diagnostics ...........................................................47
Display Diagnostics .........................................................49
Boot Diagnostics ............................................................50
Network Diagnostics ........................................................50
e Emergency Kernel .......................................................53
CHAPTER 4
Network Conguration ................................. 55
Wired Networking ..........................................................56
Wireless Networking ........................................................59
No Encryption ........................................................68
WEP Encryption .......................................................68
WPA/WPA2 Encryption ................................................69
Connecting to the Wireless Network .....................................69
CHAPTER 5
Partition Management................................. 71
Creating a New Partition .....................................................72
Resizing Existing Partitions ...................................................76
Automatic Resizing .......................................................76
Manual Resizing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
Moving to a Bigger SD Card ..................................................81
Imaging from Linux .......................................................82
Imaging from OS X .......................................................83
Imaging from Windows ...................................................83
CHAPTER 6
Conguring the Raspberry Pi............................ 85
Hardware Settings—cong.txt ................................................86
Modifying the Display .....................................................87
Boot Options ............................................................90
Overclocking the Raspberry Pi ..............................................91
Overclocking Settings ..................................................92
Overvoltage Settings ...................................................93
Disabling L2 Cache .......................................................94
Enabling Test Mode ......................................................95
Memory Partitioning—start.elf ...............................................96
Software Settings—cmdline.txt ...............................................97
www.allitebooks.com
TABLE OF CONTENTS
Part II: Using the Pi as a Media Centre,
Productivity Machine and Web Server
CHAPTER 7
The Pi as a Home Theatre PC ........................... 103
Playing Music at the Console ................................................104
Dedicated HTPC with Rasbmc ...............................................106
Streaming Internet Media ................................................108
Streaming Local Network Media ...........................................109
Conguring Rasbmc .....................................................111
CHAPTER 8
The Pi as a Productivity Machine ........................ 113
Using Cloud-Based Apps ....................................................114
Using OpenOce.org .......................................................117
Image Editing with e Gimp ................................................119
CHAPTER 9
The Pi as a Web Server............................... 123
Installing a LAMP Stack .....................................................124
Installing WordPress .......................................................128
xiii
Part III: Programming and Hacking
CHAPTER 10
An Introduction to Scratch ............................. 135
Introducing Scratch ........................................................136
Example 1: Hello World .....................................................137
Example 2: Animation and Sound ............................................140
Example 3: A Simple Game ..................................................143
Robotics and Sensors .......................................................149
Sensing with the PicoBoard ...............................................149
Robotics with LEGO .....................................................150
Further Reading ...........................................................150
CHAPTER 11
An Introduction to Python............................. 151
Introducing Python ........................................................152
Example 1: Hello World .....................................................152
Example 2: Comments, Inputs, Variables and Loops ............................158
xiv
RASPBERRY PI USER GUIDE
Example 3: Gaming with pygame .............................................162
Example 4: Python and Networking ..........................................171
Further Reading ...........................................................178
CHAPTER 12
Hardware Hacking .................................. 179
Electronic Equipment .......................................................180
Reading Resistor Colour Codes ...............................................182
Sourcing Components ......................................................184
Online Sources ..........................................................184
Oine Sources ..........................................................185
Hobby Specialists ........................................................186
e GPIO Port .............................................................186
UART Serial Bus .........................................................188
I²C Bus .................................................................189
SPI Bus ................................................................189
Using the GPIO Port in Python ..............................................189
Installing the GPIO Python Library ........................................190
GPIO Output: Flashing an LED ............................................192
GPIO Input: Reading a Button .............................................196
Moving Up From the Breadboard .............................................200
A Brief Guide to Soldering ...................................................203
CHAPTER 13
Add-on Boards..................................... 209
Ciseco Slice of Pi ...........................................................210
Adafruit Prototyping Pi Plate ................................................214
Fen Logic Gertboard ........................................................217
Part IV: Appendixes
APPENDIX A
Python Recipes ..................................... 225
Raspberry Snake (Chapter 11, Example 3) .....................................226
IRC User List (Chapter 11, Example 4) ........................................228
GPIO Input and Output (Chapter 12) .........................................230
APPENDIX B
HDMI Display Modes ................................. 231
Index............................................ 237
Introduction
“CHILDREN TODAY ARE digital natives”, said a man I got talking to at a reworks
party last year. “I don’t understand why you’re making this thing. My kids know more
about setting up our PC than I do.”
I asked him if they could program, to which he replied: “Why would they want to? e
computers do all the stu they need for them already, don’t they? Isn’t that the point?”
As it happens, plenty of kids today aren’t digital natives. We have yet to meet any of
these imagined wild digital children, swinging from ropes of twisted-pair cable and
chanting war songs in nicely parsed Python. In the Raspberry Pi Foundation’s educational outreach work, we do meet a lot of kids whose entire interaction with technology
is limited to closed platforms with graphical user interfaces (GUIs) that they use to play
movies, do a spot of word-processed homework and play games. ey can browse the
web, upload pictures and video, and even design web pages. (ey’re often better at setting the satellite TV box than Mum or Dad, too.) It’s a useful toolset, but it’s shockingly
incomplete, and in a country where 20% of households still don’t have a computer in the
home, even this toolset is not available to all children.
Despite the most fervent wishes of my new acquaintance at the reworks party, computers don’t program themselves. We need an industry full of skilled engineers to keep
technology moving forward, and we need young people to be taking those jobs to ll
the pipeline as older engineers retire and leave the industry. But there’s much more to
teaching a skill like programmatic thinking than breeding a new generation of coders
and hardware hackers. Being able to structure your creative thoughts and tasks in
complex, non-linear ways is a learned talent, and one that has huge benets for everyone who acquires it, from historians to designers, lawyers and chemists.
Programming is fun!
It’s enormous, rewarding, creative fun. You can create gorgeous intricacies, as well as
(much more gorgeous, in my opinion) clever, devastatingly quick and deceptively simplelooking routes through, under and over obstacles. You can make stu that’ll have other
2
RASPBERRY PI USER GUIDE
people looking on jealously, and that’ll make you feel wonderfully smug all afternoon. In my
day job, where I design the sort of silicon chips that we use in the Raspberry Pi as a processor
and work on the low-level software that runs on them, I basically get paid to sit around all day
playing. What could be better than equipping people to be able to spend a lifetime doing that?
It’s not even as if we’re coming from a position where children don’t want to get involved in
the computer industry. A big kick up the backside came a few years ago, when we were moving quite slowly on the Raspberry Pi project. All the development work on Raspberry Pi was
done in the spare evenings and weekends of the Foundation’s trustees and volunteers—
we’re a charity, so the trustees aren’t paid by the Foundation, and we all have full-time jobs
to pay the bills. is meant that occasionally, motivation was hard to come by when all I
wanted to do in the evening was slump in front of the Arrested Development boxed set with a
glass of wine. One evening, when not slumping, I was talking to a neighbour’s nephew about
the subjects he was taking for his General Certicate of Secondary Education (GCSE, the
British system of public examinations taken in various subjects from the age of about 16),
and I asked him what he wanted to do for a living later on.
“I want to write computer games”, he said.
“Awesome. What sort of computer do you have at home? I’ve got some programming books
you might be interested in.”
“A Wii and an Xbox.”
On talking with him a bit more, it became clear that this perfectly smart kid had never done
any real programming at all; that there wasn’t any machine that he could program in the
house; and that his information and communication technology (ICT) classes—where he
shared a computer and was taught about web page design, using spreadsheets and word processing—hadn’t really equipped him to use a computer even in the barest sense. But computer games were a passion for him (and there’s nothing peculiar about wanting to work on
something you’re passionate about). So that was what he was hoping the GCSE subjects he’d
chosen would enable him to do. He certainly had the artistic skills that the games industry
looks for, and his maths and science marks weren’t bad. But his schooling had skirted around
any programming—there were no Computing options on his syllabus, just more of the same
ICT classes, with its emphasis on end users rather than programming. And his home interactions with computing meant that he stood a vanishingly small chance of acquiring the skills
he needed in order to do what he really wanted to do with his life.
is is the sort of situation I want to see the back of, where potential and enthusiasm is
squandered to no purpose. Now, obviously, I’m not monomaniacal enough to imagine that simply making the Raspberry Pi is enough to eect all the changes that are needed. But I do believe
that it can act as a catalyst. We’re already seeing big changes in the UK schools’ curriculum,
INTRODUCTION
where Computing is arriving on the syllabus and ICT is being reshaped, and we’ve seen a massive
change in awareness of a gap in our educational and cultural provision for kids just in the short
time since the Raspberry Pi was launched.
Too many of the computing devices a child will interact with daily are so locked down that they
can’t be used creatively as a tool—even though computing is a creative subject. Try using your
iPhone to act as the brains of a robot, or getting your PS3 to play a game you’ve written. Sure,
you can program the home PC, but there are signicant barriers in doing that which a lot of
children don’t overcome: the need to download special software, and having the sort of parents
who aren’t worried about you breaking something that they don’t know how to x. And plenty
of kids aren’t even aware that doing such a thing as programming the home PC is possible. ey
think of the PC as a machine with nice clicky icons that give you an easy way to do the things
you need to do so you don’t need to think much. It comes in a sealed box, which Mum and Dad
use to do the banking and which will cost lots of money to replace if something goes wrong!
e Raspberry Pi is cheap enough to buy with a few weeks’ pocket money, and you probably
have all the equipment you need to make it work: a TV, an SD card that can come from an old
camera, a mobile phone charger, a keyboard and a mouse. It’s not shared with the family; it
belongs to the kid; and it’s small enough to put in a pocket and take to a friend’s house. If
something goes wrong, it’s no big deal—you just swap out a new SD card and your Raspberry
Pi is factory-new again. And all the tools, environments and learning materials that you need
to get started on the long, smooth curve to learning how to program your Raspberry Pi are
right there, waiting for you as soon as you turn it on.
3
A bit of history
I started work on a tiny, aordable, bare-bones computer about six years ago, when I was a
Director of Studies in Computer Science at Cambridge University. I’d received a degree at the
University Computer Lab as well as studying for a PhD while teaching there, and over that
period, I’d noticed a distinct decline in the skillset of the young people who were applying to
read Computer Science at the Lab. From a position in the mid-1990s, when 17-year-olds
wanting to read Computer Science had come to the University with a grounding in several
computer languages, knew a bit about hardware hacking, and often even worked in assembly
language, we gradually found ourselves in a position where, by 2005, those kids were arriving
having done some HTML—with a bit of PHP and Cascading Style Sheets if you were lucky.
ey were still fearsomely clever kids with lots of potential, but their experience with computers was entirely dierent from what we’d been seeing before.
e Computer Science course at Cambridge includes about 60 weeks of lecture and seminar
time over three years. If you’re using the whole rst year to bring students up to speed, it’s
harder to get them to a position where they can start a PhD or go into industry over the next
4
RASPBERRY PI USER GUIDE
two years. e best undergraduates—the ones who performed the best at the end of their
three-year course—were the ones who weren’t just programming when they’d been told to
for their weekly assignment or for a class project. ey were the ones who were programming
in their spare time. So the initial idea behind the Raspberry Pi was a very parochial one with
a very tight (and pretty unambitious) focus: I wanted to make a tool to get the small number
of applicants to this small university course a kick start. My colleagues and I imagined we’d
hand out these devices to schoolkids at open days, and if they came to Cambridge for an
interview a few months later, we’d ask what they’d done with the free computer we’d given
them. ose who had done something interesting would be the ones that we’d be interested
in having in the program. We thought maybe we’d make a few hundred of these devices, or
best case, a lifetime production run of a few thousand.
Of course, once work was seriously underway on the project, it became obvious that there was
a lot more we could address with a cheap little computer like this. What we started with is a
long way indeed from the Raspberry Pi you see today. I began by soldering up the longest piece
of breadboard you can buy at Maplin with an Atmel chip at our kitchen table, and the rst
crude prototypes used cheap microcontroller chips to drive a standard-denition TV set
directly. With only 512 K of RAM, and a few MIPS of processing power, these prototypes were
very similar in performance to the original 8-bit microcomputers. It was hard to imagine these
machines capturing the imaginations of kids used to modern games consoles and iPads.
ere had been discussions at the University Computer Lab about the general state of computer education, and when I left the Lab for a non-academic job in the industry, I noticed
that I was seeing the same issues in young job applicants as I’d been seeing at the University.
So I got together with my colleagues Dr Rob Mullins and Professor Alan Mycroft (two colleagues from the Computer Lab), Jack Lang (who lectures in entrepreneurship at the
University), Pete Lomas (a hardware guru) and David Braben (a Cambridge games industry
leading light with an invaluable address book), and over beers (and, in Jack’s case, cheese and
wine), we set up the Raspberry Pi Foundation—a little charity with big ideas.
Why “Raspberry Pi”?
We get asked a lot where the name “Raspberry Pi” came from. Bits of the name came from
different trustees. It’s one of the very few successful bits of design by committee I’ve seen,
and to be honest, I hated it at first. (I have since come to love the name, because it works really
well—but it took a bit of getting used to since I’d been calling the project the “ABC Micro” in
my head for years.) It’s “Raspberry” because there’s a long tradition of fruit names in computer
companies (besides the obvious, there are the old Tangerine and Apricot computers—and we
like to think of the Acorn as a fruit as well). “Pi” is a mangling of “Python”, which we thought
early on in development would be the only programming language available on a much less
powerful platform than the Raspberry Pi we ended up with. As it happens, we still recommend
Python as our favourite language for learning and development, but there is a world of other
language options you can explore on the Raspberry Pi too.
INTRODUCTION
In my new role as a chip architect at Broadcom, a big semiconductor company, I had access to
inexpensive but high-performing hardware produced by the company with the intention of
being used in very high-end mobile phones—the sort with the HD video and the 14-megapixel
cameras. I was amazed by the dierence between the chips you could buy for $10 as a small
developer, and what you could buy as a cell-phone manufacturer for roughly the same amount
of money: general purpose processing, 3D graphics, video and memory bundled into a single
BGA package the size of a ngernail. ese microchips consume very little power, and have big
capabilities. ey are especially good at multimedia, and were already being used by set-top box
companies to play high-denition video. A chip like this seemed the obvious next step for the
shape the Raspberry Pi was taking, so I worked on taping out a low-cost variant that had an
ARM microprocessor on board and could handle the processing grunt we needed.
We felt it was important to have a way to get kids enthusiastic about using a Raspberry Pi
even if they didn’t feel very enthusiastic about programming. In the 1980s, if you wanted to
play a computer game, you had to boot up a box that went “bing” and fed you a command
prompt. It required typing a little bit of code just to get started, and most users didn’t ever go
beyond that—but some did, and got beguiled into learning how to program by that little bit
of interaction. We realised that the Raspberry Pi could work as a very capable, very tiny, very
cheap modern media centre, so we emphasised that capability to suck in the unwary—with
the hope that they’d pick up some programming while they’re at it.
5
After about ve years’ hard grind, we had created a very cute prototype board, about the size of
a thumb drive. We included a permanent camera module on top of the board to demonstrate
the sort of peripherals that can easily be added, and brought it along to a number of meetings
with the BBC’s R&D department. ose of us who grew up in the UK in the 1980s had learned
a lot about 8-bit computing from the BBC Microcomputer and the ecosystem that had grown
up around it—with BBC-produced books, magazines and TV programmes—so I’d hoped that
they might be interested in developing the Raspberry Pi further. But as it turned out, something has changed since we were kids: various competition laws in the UK and the EU meant
that “the Beeb” couldn’t become involved in the way we’d hoped. In a last-ditch attempt to get
something organised with them, we ditched the R&D department idea and David (he of the
giant address book) organised a meeting with Rory Cellan-Jones, a senior tech journalist, in
May 2011. Rory didn’t hold out much hope for partnership with the BBC, but he did ask if he
could take a video of the little prototype board with his phone, to put on his blog.
e next morning, Rory’s video had gone viral, and I realised that we had accidentally promised the world that we’d make everybody a $25 computer.
While Rory went o to write another blog post on exactly what it is that makes a video go
viral, we went o to put our thinking caps on. at original, thumb-drive-sized prototype
didn’t t the bill: with the camera included as standard, it was way too expensive to meet the
6
RASPBERRY PI USER GUIDE
cost model we’d suggested (the $25 gure came from my statement to the BBC that the
Raspberry Pi should cost around the same as a text book, and is a splendid demonstration of
the fact that I had no idea how much text books cost these days), and the tiny prototype
model didn’t have enough room around its periphery for all the ports we needed to make it
as useable as we wanted it to be. So we spent a year working on engineering the board to
lower cost as much as possible while retaining all the features we wanted (engineering cost
down is a harder job than you might think), and to get the Raspberry Pi as useable as possible
for people who might not be able to aord much in the way of peripherals.
We knew we wanted the Raspberry Pi to be used with TVs at home, just like the ZX Spectrum in
the 1980s, saving the user the cost of a monitor. But not everybody has access to an HDMI television, so we added a composite port to make the Raspberry Pi work with an old cathode-ray television instead since SD cards are cheap and easy to nd. We decided against microSD as the storage
medium, because the little ngernail-sized cards are so imsy in the hands of children and so easy
to lose. And we went through several iterations of power supply, ending up with a micro USB
cable. Recently, micro USB became the standard charger cable for mobile telephones across the
EU (and it’s becoming the standard everywhere), which means the cables are becoming more and
more ubiquitous, and in many cases, people already have them at home.
By the end of 2011, with a projected February release date, it was becoming obvious to us that
things were moving faster, and demand was higher, than we were ever going to be able to cope
with. e initial launch was always aimed at developers, with the educational launch planned
for later in 2012. We have a small number of very dedicated volunteers, but we need the wider
Linux community to help us prepare a software stack and iron out any early-life niggles with
the board before releasing into the educational market. We had enough capital in the
Foundation to buy the parts for and build 10,000 Raspberry Pis over a period of a month or so,
and we thought that the people in the community who would be interested in an early board
would come to around that number. Fortunately and unfortunately, we’d been really successful
in building a big online community around the device, and interest wasn’t limited to the UK, or
to the educational market. Ten thousand was looking less and less realistic.
Our Community
The Raspberry Pi community is one of the things we’re proudest of. We started with a
very bare-bones blog at www.raspberrypi.org just after Rory’s May 2011 video, and put
up a forum on the same website shortly after that. That forum now has more than 20,000
members—between them they’ve contributed more than 100,000 posts of wit and wisdom
about the Raspberry Pi. If there’s any question, no matter how abstruse, that you want to ask
about the Raspberry Pi or about programming in general, someone there will have the answer
(if it’s not in this book, you’ll find it in the forums).
INTRODUCTION
Part of my job at Raspberry Pi involves giving talks to hacker groups, computing conferences,
teachers, programming collectives and the like, and there’s always someone in the audience
who has talked to me or to my wife Liz (who runs the community) on the Raspberry Pi
website—and some of these people have become good friends of ours. The Raspberry Pi
website gets around one request every single second of the day.
There are now hundreds of fan sites out there. There’s also a fan magazine called The MagPi (a
free download from www.themagpi.com), which is produced monthly by community members,
with type-in listings, lots of articles, project guides, tutorials and more. Type-in games in magazines
and books provided an easy route into programming for me—my earliest programming experience
with the BBC Micro was of modifying a type-in helicopter game to add enemies and pick-ups.
We blog something interesting about the device at www.raspberrypi.org at least once
every day. Come and join in the conversation!
ere were 100,000 people on our mailing list wanting a Raspberry Pi—and they all put an
order in on day one! Not surprisingly, this brought up a few issues.
First o, there are the inevitable paper cuts you’re going to get boxing up 100,000 little computers
and mailing them out—and the fact was that we had absolutely no money to hire people to do
this for us. We didn’t have a warehouse—we had Jack’s garage. ere was no way we could raise
the money to build 100,000 units at once—we’d envisaged making them in batches of 2,000
every couple of weeks, which, with this level of interest, was going to take so long that the thing
would be obsolete before we managed to full all the orders. Clearly, manufacturing and distribution were something we were going to have to give up on and hand over to somebody else who
already had the infrastructure and capital to do that, so we got in touch with element14 and RS
Components, both UK microelectronics suppliers with worldwide businesses, and contracted
with them to do the actual manufacture and distribution side of things worldwide so we could
concentrate on development and the Raspberry Pi Foundation’s charitable goals.
7
Demand on the rst day was still so large that RS and element14’s websites both crashed for
most of the day—at one point in the day, element14 were getting seven orders a second, and
for a couple of hours on February 29, Google showed more searches were made worldwide
for “Raspberry Pi” than were made for “Lady Gaga”. I’m writing this in early June 2012, and
orders in the three months since we opened for business have topped half a million units,
even though we’re still at a point when neither company will sell you more than one
Raspberry Pi (they’re trying to get rid of their order backlogs before they turn on the ability
to multiorder). At this point, if we’d gone with our original plans, we’d have made 100 or so
of these devices for University open days, and that would have been it.
ere is nothing that aects the blood pressure quite like accidentally ending up running a
large computer company!
8
RASPBERRY PI USER GUIDE
So what can you do with the Raspberry Pi?
is book explores a number of things you can do with your Raspberry Pi, from controlling
hardware with Python, to using it as a media centre, or building games in Scratch. e beauty of
the Raspberry Pi is that it’s just a very tiny general-purpose computer (which may be a little
slower than you’re used to for some desktop applications, but much better at some other stu
than a regular PC), so you can do anything you could do on a regular computer with it. In addition, the Raspberry Pi has powerful multimedia and 3D graphics capabilities, so it has the
potential to be used as a games platform, and we very much hope to see people starting to write
games for it.
We think physical computing—building systems using sensors, motors, lights and microcontrollers—is something that gets overlooked in favour of pure software projects in a lot of
instances, and it’s a shame, because physical computing is massive fun. To the extent that there’s
any children’s computing movement at the moment, it’s a physical computing movement. e
LOGO turtles that represented physical computing when we were kids are now ghting robots,
quadcopters or parent-sensing bedroom doors, and we love it. However, the lack of General
Purpose Input/Output (GPIO) on home PCs is a real handicap for many people getting started
with robotics projects. e Raspberry Pi exposes GPIO so you can get to work straight away.
I keep being surprised by ideas the community comes up with which wouldn’t have crossed
my mind in a thousand years: the Australian school meteor-tracking project; the Boreatton
Scouts in the UK and their robot, which is controlled via an electroencephalography headset
(the world’s rst robot controlled by Scouting brain waves); the family who are building a
robot vacuum cleaner. And I’m a real space cadet, so reading about the people sending
Raspberry Pis into near-earth orbit on rockets and balloons gives me goosebumps.
Success for us would be another 1,000 people every year taking up Computer Science at the
university level in the UK. at would not only be benecial for the country, the software
and hardware industries, and the economy; but it would be even more benecial for every
one of those 1,000 people, who, I hope, discover that there’s a whole world of possibilities
and a great deal of fun to be had out there. Building a robot when you’re a kid can take you to
places you never imagined—I know because it happened to me!
—Eben Upton
Part I
Connecting
the Board
Chapter 1 Meet the Raspberry Pi
Chapter 2 Linux System Administration
Chapter 3 Troubleshooting
Chapter 4 Network Conguration
Chapter 5 Partition Management
Chapter 6 Conguring the Raspberry Pi
Chapter 1
Meet the Raspberry Pi
12
RASPBERRY PI USER GUIDE
YOUR RASPBERRY PI board is a miniature marvel, packing considerable computing power
into a footprint no larger than a credit card. It’s capable of some amazing things, but there are
a few things you’re going to need to know before you plunge head-rst into the bramble patch.
TIP
F -:
e BCM2835
SoC, located
beneath a Hynix
memory chip
If you’re eager to get started, skip ahead a couple of pages to find out how to connect your
Raspberry Pi to a display, keyboard and mouse.
ARM vs. x86
e processor at the heart of the Raspberry Pi system is a Broadcom BCM2835 system-onchip (SoC) multimedia processor. is means that the vast majority of the system’s components, including its central and graphics processing units along with the audio and
communications hardware, are built onto that single component hidden beneath the 256
MB memory chip at the centre of the board (see Figure 1-1).
It’s not just this SoC design that makes the BCM2835 dierent to the processor found in
your desktop or laptop, however. It also uses a dierent instruction set architecture (ISA),
known as ARM.
CHAPTER 1 MEET THE RASPBERRY PI
Developed by Acorn Computers back in the late 1980s, the ARM architecture is a relatively
uncommon sight in the desktop world. Where it excels, however, is in mobile devices: the
phone in your pocket almost certainly has at least one ARM-based processing core hidden
away inside. Its combination of a simple reduced instruction set (RISC) architecture and low
power draw make it the perfect choice over desktop chips with high power demands and
complex instruction set (CISC) architectures.
e ARM-based BCM2835 is the secret of how the Raspberry Pi is able to operate on just the
5V 1A power supply provided by the onboard micro-USB port. It’s also the reason why you
won’t nd any heat-sinks on the device: the chip’s low power draw directly translates into
very little waste heat, even during complicated processing tasks.
It does, however, mean that the Raspberry Pi isn’t compatible with traditional PC software.
e majority of software for desktops and laptops is built with the x86 instruction set architecture in mind, as found in processors from the likes of AMD, Intel and VIA. As a result, it
won’t run on the ARM-based Raspberry Pi.
e BCM2835 uses a generation of ARM’s processor design known as ARM11, which in turn is
designed around a version of the instruction set architecture known as ARMv6. is is worth
remembering: ARMv6 is a lightweight and powerful architecture, but has a rival in the more
advanced ARMv7 architecture used by the ARM Cortex family of processors. Software developed for ARMv7, like software developed for x86, is sadly not compatible with the Raspberry
Pi’s BCM2835—although developers can usually convert the software to make it suitable.
13
at’s not to say you’re going to be restricted in your choices. As you’ll discover later in the
book, there is plenty of software available for the ARMv6 instruction set, and as the Raspberry
Pi’s popularity continues to grow, that will only increase. In this book, you’ll also learn how to
create your own software for the Pi even if you have no experience with programming.
Windows vs. Linux
Another important dierence between the Raspberry Pi and your desktop or laptop, other than
the size and price, is the operating system—the software that allows you to control the computer.
e majority of desktop and laptop computers available today run one of two operating systems: Microsoft Windows or Apple OS X. Both platforms are closed source, created in a secretive environment using proprietary techniques.
ese operating systems are known as closed source for the nature of their source code, the
computer-language recipe that tells the system what to do. In closed-source software, this
recipe is kept a closely-guarded secret. Users are able to obtain the nished software, but
never to see how it’s made.
14
RASPBERRY PI USER GUIDE
e Raspberry Pi, by contrast, is designed to run an operating system called GNU/Linux—
hereafter referred to simply as Linux. Unlike Windows or OS X, Linux is open source: it’s
possible to download the source code for the entire operating system and make whatever
changes you desire. Nothing is hidden, and all changes are made in full view of the public.
is open source development ethos has allowed Linux to be quickly altered to run on the
Raspberry Pi, a process known as porting. At the time of this writing, several versions of
Linux—known as distributions—have been ported to the Raspberry Pi’s BCM2835 chip,
including Debian, Fedora Remix and Arch Linux.
e dierent distributions cater to dierent needs, but they all have something in common:
they’re all open source. ey’re also all, by and large, compatible with each other: software
written on a Debian system will operate perfectly well on Arch Linux and vice versa.
Linux isn’t exclusive to the Raspberry Pi. Hundreds of dierent distributions are available for
desktops, laptops and even mobile devices; and Google’s popular Android platform is developed on top of a Linux core. If you nd that you enjoy the experience of using Linux on the
Raspberry Pi, you could consider adding it to other computing devices you use as well. It will
happily coexist with your current operating system, allowing you to enjoy the benets of
both while giving you a familiar environment when your Pi is unavailable.
As with the dierence between ARM and x86, there’s a key point to make about the practical
dierence between Windows, OS X and Linux: software written for Windows or OS X won’t
run on Linux. ankfully, there are plenty of compatible alternatives for the overwhelming
majority of common software products—better still, the majority are free to use and as open
source as the operating system itself.
Getting Started with the Raspberry Pi
Now that you have a basic understanding of how the Pi diers from other computing devices,
it’s time to get started. If you’ve just received your Pi, take it out of its protective anti-static
bag and place it on a at, non-conductive surface before continuing with this chapter.
Connecting a Display
Before you can start using your Raspberry Pi, you’re going to need to connect a display. e
Pi supports three dierent video outputs: composite video, HDMI video and DSI video.
Composite video and HDMI video are readily accessible to the end user, as described in this
section, while DSI video requires some specialised hardware.
Composite Video
Composite video, available via the yellow-and-silver port at the top of the Pi known as an
RCA phono connector (see Figure 1-2), is designed for connecting the Raspberry Pi to older
display devices. As the name suggests, the connector creates a composite of the colours
CHAPTER 1 MEET THE RASPBERRY PI
found within an image—red, green and blue—and sends it down a single wire to the display
device, typically an old cathode-ray tube (CRT) TV.
15
F -:
e yellow
RCA phono
connector, for
composite video
output
When no other display device is available, a composite video connection will get you started
with the Pi. e quality, however, isn’t great. Composite video connections are signicantly
more prone to interference, lack clarity and run at a limited resolution, meaning that you can
t fewer icons and lines of text on the screen at once.
HDMI Video
A better-quality picture can be obtained using the HDMI (High Definition Multimedia Interface)
connector, the only port found on the bottom of the Pi (see Figure 1-3). Unlike the analogue
composite connection, the HDMI port provides a high-speed digital connection for pixelperfect pictures on both computer monitors and high-denition TV sets. Using the HDMI
port, a Pi can display images at the Full HD 1920x1080 resolution of most modern HDTV
sets. At this resolution, signicantly more detail is available on the screen.
If you’re hoping to use the Pi with an existing computer monitor, you may nd that your display doesn’t have an HDMI input. at’s not a disaster: the digital signals present on the HDMI
cable map to a common computer monitor standard called DVI (Digital Video Interconnect). By
purchasing an HDMI-to-DVI cable, you’ll be able to connect the Pi’s HDMI port to a monitor
with DVI-D connectivity.
16
RASPBERRY PI USER GUIDE
F -:
e silver HDMI
connector, for
high-denition
video output
If your monitor has a VGA input—a D-shaped connector with 15 pins, typically coloured silver
and blue—the Raspberry Pi can’t connect to it. Adapters are available that will take in a digital
DVI signal and convert it to an analogue VGA signal, but these are expensive and bulky. e
best option here is simply to buy a more-modern monitor with a DVI or HDMI input.
DSI Video
e nal video output on the Pi can be found above the SD card slot on the top of the printed
circuit board—it’s a small ribbon connector protected by a layer of plastic. is is for a video
standard known as Display Serial Interface (DSI), which is used in the at-panel displays of
tablets and smartphones. Displays with a DSI connector are rarely available for retail purchase, and are typically reserved for engineers looking to create a compact, self-contained
system. A DSI display can be connected by inserting a ribbon cable into the matched connector on the Pi, but for beginners, the use of a composite or HDMI display is recommended.
Connecting Audio
If you’re using the Raspberry Pi’s HDMI port, audio is simple: when properly congured, the
HDMI port carries both the video signal and a digital audio signal. is means that you can
connect a single cable to your display device to enjoy both sound and pictures.
CHAPTER 1 MEET THE RASPBERRY PI
Assuming you’re connecting the Pi to a standard HDMI display, there’s very little to do at
this point. For now, it’s enough to simply connect the cable.
If you’re using the Pi with a DVI-D monitor via an adapter or cable, audio will not be included.
is highlights the main dierence between HDMI and DVI: while HDMI can carry audio
signals, DVI cannot.
For those with DVI-D monitors, or those using the composite video output, a black 3.5 mm
audio jack located on the top edge of the Pi next to the yellow phono connector provides analogue audio (see Figure 1-2). is is the same connector used for headphones and microphones on consumer audio equipment, and it’s wired in exactly the same way. If you want,
you can simply connect a pair of headphones to this port for quick access to audio.
17
While headphones can be connected directly to the Raspberry Pi, you may find the volume a
little lacking. If possible, connect a pair of powered speakers instead. The amplifier inside will
help boost the signal to a more audible level.
If you’re looking for something more permanent, you can either use standard PC speakers
that have a 3.5 mm connector or you can buy some adapter cables. For composite video
users, a 3.5 mm to RCA phono cable is useful. is provides the two white-and-red RCA
phono connections that sit alongside the video connection, each carrying a channel of the
stereo audio signal to the TV.
For those connecting the Pi to an amplier or stereo system, you’ll either need a 3.5 mm to
RCA phono cable or a 3.5 mm to 3.5 mm cable, depending on what spare connections you
have on your system. Both cable types are readily and cheaply available at consumer electronics shops, or can be purchased even cheaper at online retailers such as Amazon.
Connecting a Keyboard and Mouse
Now that you’ve got your Raspberry Pi’s output devices sorted, it’s time to think about input.
As a bare minimum, you’re going to need a keyboard, and for the majority of users, a mouse
or trackball is a necessity too.
First, some bad news: if you’ve got a keyboard and mouse with a PS/2 connector—a round
plug with a horseshoe-shaped array of pins—then you’re going to have to go out and buy a
replacement. e old PS/2 connection has been superseded, and the Pi expects your peripherals to be connected over the Universal Serial Bus (USB) port.
TIP
Depending on whether you purchased the Model A or Model B, you’ll have either one or two
USB ports available on the right side of the Pi (see Figure 1-4). If you’re using Model B, you
18
RASPBERRY PI USER GUIDE
can connect the keyboard and mouse directly to these ports. If you’re using Model A, you’ll
need to purchase a USB hub in order to connect two USB devices simultaneously.
F -:
Model B’s two
USB ports
TIP
A USB hub is a good investment for any Pi user: even if you’ve got a Model B, you’ll use up
both your available ports just connecting your keyboard and mouse, leaving nothing free for
additional devices such as an external optical drive, storage device or joystick. Make sure you
buy a powered USB hub: passive models are cheaper and smaller, but lack the ability to run
current-hungry devices like CD drives and external hard drives.
If you want to reduce the number of power sockets in use, connect the Raspberry Pi’s USB
power lead to your powered USB hub. This way, the Pi can draw its power directly from the
hub, rather than needing its own dedicated power socket and mains adapter. This will only
work on hubs with a power supply capable of providing 700mA to the Pi’s USB port, along with
whatever power is required by other peripherals.
Connecting the keyboard and mouse is as simple as plugging them in to the USB ports, either
directly in the case of a Model B or via a USB hub in the case of a Model A.
www.allitebooks.com
Loading...