This edition first published 2016

© 2016 Eben Upton and Gareth Halfacree

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About the Technical Editor

ANDREW SCHELLER is a freelance software developer based in Cambridge in the UK. He has worked on many projects for a variety of clients, including updating the Raspberry Pi NOOBS software to run on the Raspberry Pi 2. Prior to going freelance, he served as a tools programmer for Sony Computer Entertainment, working on a number of titles, including MediEvil Resurrection for the PlayStation Portable and 24: The Game for the PlayStation 2. While there he developed a localisation system which has become adopted as the standard by all Sony game studios worldwide. He spends some of his free time working on open source software, and has been using Linux for more than 20 years. He enjoys walking, cycling, and climbing, and holds a BSc (Hons) in Computer Science from Durham University.

For Liz, who made it all possible.
—Eben

For my father, the enthusiastic past, and my daughters, the exciting future.
—Gareth

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 simple-looking routes through, under, and over obstacles. You can make stuff that’ll have other 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. This 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 Certificate 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.

This 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 effect all the changes that are needed. But I do believe that it can act as a catalyst. We’ve already seen big changes in UK schools, where a revamped Computing curriculum arrived on the syllabus in 2014, and we’ve seen a massive change in awareness of a gap in our educational and cultural provision for kids just in the four years since the first 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 PS4 to play a game you’ve written. Sure, you can program the home PC, but there are significant 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 fix. And plenty of kids aren’t even aware that doing such a thing as programming the home PC is possible. They 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!

The Raspberry Pi is cheap enough to buy with a few weeks’ pocket money, and you probably already 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.

A Bit of History

I started work on a tiny, affordable, bare-bones computer in 2006, 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. They were still fearsomely clever kids with lots of potential, but their experience with computers was entirely different from what we’d been seeing before.

The Computer Science course at Cambridge includes about 60 weeks of lecture and seminar time over three years. If you’re using the whole first 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 two years. The 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. They 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. Those 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 first crude prototypes used cheap microcontroller chips to drive a standard-definition 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.

There 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.

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 what were then very high-end mobile phones—the sort with the HD video and the 14-megapixel cameras. I was amazed by the difference 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 fingernail. These microchips consume very little power, and have big capabilities. They are especially good at multimedia, and were already being used by set-top box companies to play high-definition 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.

After about five 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 (there was no camera when we launched because it brought the price up too much, but we’ve now made a separate, cheap camera module available for photography projects), and brought it along to a number of meetings with the BBC’s R&D department. Those 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.

The 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 off to write another blog post on exactly what it is that makes a video go viral, we went off to put our thinking caps on. That original, thumb-drive-sized prototype didn’t fit the bill: with the camera included as standard, it was way too expensive to meet the cost model we’d suggested (the $25 figure 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 afford 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 find, we chose them as our storage medium: the original Model A and Model B used full-size cards, while more recent iterations have moved to the now more common microSD standard. 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. The initial launch was always aimed at developers, with the educational launch planned for later in 2012. We had a small number of very dedicated volunteers, but we needed 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.

There 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 off, 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. There 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 fulfil 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.

Demand on the first 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”. We made and sold more than a million Raspberry Pis in the first year of business, making Raspberry Pi the fastest-growing computer company in the world, ever. Things aren’t slowing down: we make more than 300,000 Pis every month and have sold more than ten million in a little over four, with no hint of a slowdown. If we’d stuck with our original plans, we’d have made 100 or so of these devices for University open days, and that would have been it.

So What Can You Do with the Raspberry Pi?

This 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, setting up camera projects, or building games in Scratch. The 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 stuff 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 more 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 was any children’s computing movement when we began this project, it was a physical computing movement. The LOGO turtles that represented physical computing when we were kids are now fighting 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. The 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 first robot controlled by Scouting brain waves); the family who are building a robot vacuum cleaner; Manuel, the talking Christmas moose. 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.

In the first edition of this book, I said that success for us would be another 1,000 people every year taking up Computer Science at the university level in the UK. That would not only be beneficial for the country, the software and hardware industries, and the economy; but it would be even more beneficial 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. In the second edition and third editions, I was a little more ambitious, saying that we’d like to see that replicated throughout the developed world. As Raspberry Pi has grown, however, I’ve become even more ambitious: I want every child, everywhere, to have access to an open, programmable, general-purpose computer, and to have the opportunity to learn to program in the same way that I did on my BBC Microcomputer back in the 1980s. It’s a lofty goal, but we’ve already seen Raspberry Pi labs spring up in the most unlikely places, like a village lab in a part of Cameroon with no electricity network where the Pis run off solar power, generators, and batteries, or a school high in the mountains in Bhutan.

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

The Board

Chapter 1 Meet the Raspberry Pi

Chapter 2 Getting Started with Raspberry Pi

Chapter 3 Linux System Administration

Chapter 4 Troubleshooting

Chapter 5 Network Configuration

Chapter 6 The Raspberry Pi Configuration Tool

Chapter 7 Advanced Raspberry Pi Configuration

A Trip Around the Board

Since its launch as a mere two models, the Raspberry Pi family has expanded considerably. The current range consists of five mainstream models: the Raspberry Pi Model A+, Raspberry Pi Model B+, Raspberry Pi 2, Raspberry Pi 3 (see Figure 1-1), and Raspberry Pi Zero. Aside from the Zero, which is a cut-down model designed specifically for the lowest-possible cost and minimum board footprint, all models share a roughly similar design differing only in features such as the number of USB ports, presence or absence of network ports, and the power of their processor. The range also has a sixth, less-common, member: the Raspberry Pi Compute Module; designed for industrial use in customised carrier boards, the Compute Module runs the same software as its mainstream stable mates, but is otherwise beyond the scope of this book.

If you are the owner of an original-model Raspberry Pi, either the Model B or cut-down Model A, congratulations: you have a collector's item on your hands. The majority of the material in this book is entirely applicable to your boards, though there are some differences, including an inability to use add-ons adhering to the Hardware Attached on Top (HAT) standard, as described in Chapter 16, “Add-On Hardware”. If you find yourself needing features missing from your early board, consider retiring it and picking up a Model A+, Model B+, or faster Raspberry Pi 2 or 3; if you're on a budget, look at the cheaper Raspberry Pi Zero.

In the rough centre of all Raspberry Pi boards is a square semiconductor, more commonly known as an integrated circuit or chip. This is the system-on-chip (SoC) module, which provides the Pi with its general-purpose processing, graphics rendering, and input/output capabilities. Depending on the model, this may be the original Broadcom BCM2835, the faster quad-core BCM2836, or the more powerful still 64-bit BCM2837. In the case of the Model A+, B+, and Zero, stacked on top of that chip is another semiconductor which provides the Pi with memory for temporary storage of data while it's running programs; on the Raspberry Pi 2 and 3, this chip is instead located on the underside of the board. This type of memory is known as random access memory (RAM), because the computer can read from or write to any part of the memory at any time. RAM is volatile, meaning that anything stored in the memory is lost when the Pi loses power or is switched off.

Below the SoC are the Pi's video outputs. The wide silver connector is a High-Definition Multimedia Interface (HDMI) port, the same type of connector found on media players and many satellite and cable set-top boxes. When connected to a modern TV or monitor, the HDMI port provides high-resolution video and digital audio. A composite video port, which is designed for connection to older TVs that don't have an HDMI socket, is provided as part of the black and silver 3.5 mm AV jack to the right of the HDMI socket. The video quality is lower than is available via HDMI, and only lower-quality analogue audio can be used. You'll need a 3.5 mm AV adapter cable to use the composite video output, but you can use the analogue audio output with any standard 3.5 mm stereo audio cable.

The Raspberry Pi Zero has a somewhat different layout. In place of a full-size HDMI socket is a mini-HDMI socket, which requires a mini-HDMI to HDMI cable or adapter to connect to a TV or monitor. The Pi Zero also lacks the 3.5 mm AV jack of the larger Pi models; there is no analogue audio output by default, and composite video is available only by soldering a cable or RCA jack to the two empty holes on the upper left of the board marked TV.

The pins to the top left of the Pi compose the general-purpose input/output (GPIO) header, which you can use to connect the Pi to other hardware. The most common use for this port is to connect an add-on board. An example, the Sense HAT, is described in Chapter 16. The GPIO port is extremely powerful, but it’s fragile. When handling the Pi, always avoid touching these pins, and never connect anything to them while the Pi is switched on.

The plastic and metal connector below the GPIO port is the Display Serial Interface (DSI) port, which is used to connect digitally driven flat-panel display systems. These are rarely used because the HDMI port is more flexible, though the official Raspberry Pi touchscreen accessory is one of the few displays to make use of the port. A second plastic and metal connector, found to the right of the HDMI port, is the Camera Serial Interface (CSI) port, which provides a high-speed connection to the Raspberry Pi Camera Module. For more details on the CSI port, see Chapter 15, “The Raspberry Pi Camera Module”.

The Pi Zero, again, has a different layout: there is no DSI port available on this model of Pi, and a compact CSI port is used in place of the full-size version found on the larger Pi models. This compact CSI port requires the use of an adapter cable or board to connect to the Raspberry Pi Camera Module. Older revisions of the Pi Zero have no CSI port at all and cannot use the Camera Module as a result.

At the very bottom left of the board is the Pi's power socket. This is a micro-USB socket, the same type found on most modern smartphones and tablets. Connecting a micro-USB cable to a suitable power adapter, detailed in Chapter 2, “Getting Started with the Raspberry Pi”, switches the Raspberry Pi on. Unlike a desktop or laptop computer, the Pi doesn't have a power switch and will start immediately when power is connected. For the Raspberry Pi Zero, the power socket is found on the far right of the board rather than the far left.

On the underside of the Raspberry Pi board on the left-hand side is a micro-SD card slot. A Secure Digital (SD) memory card provides storage for the operating system, programs, data and other files, and is non-volatile. Unlike the volatile RAM, it will retain its information even when power is lost. In Chapter 2, you'll learn how to prepare an SD card for use with the Pi, including installing an operating system in a process known as flashing. The Pi Zero has the micro-SD card slot on the top side of the board, rather than the underside.

The right-hand edge of the Pi will have different connectors depending on which model of Raspberry Pi you have; these models are described in more detail in the following pages. The board also includes one or more light-emitting diodes which provide visual feedback as to the status of the board: whether it is powered, whether it has a network connection, whether it is actively accessing the micro-SD card, and so forth.

Model A+/B+

The original Model A and B proved popular, but were quickly replaced with a new board design known as the Plus. Split into the Model A+ and Model B+ (see Figure 1-3), these revisions introduced the now-standard 40-pin GPIO header while also improving various other features; they did not, however, change from the BCM2835 SoC, meaning there is no appreciable difference in performance between the Plus variants and the older non-Plus models.

The hardware split between the Model A+ and Model B+ is similar to that of the Model A and Model B: the A+, which has a smaller footprint than the Model A, has either 256 MB or 512 MB of memory depending on when it was purchased, a single USB port, and no network capabilities; the Model B+ has 512 MB of memory, four USB ports, and a 10/100 wired network port.

The Raspberry Pi Model A+ and Model B+ are compatible with all software and devices mentioned in this book, and use the same GPIO layout as the newer-model Pi variants. If you currently own a Model A+ or Model B+, the only reason you may have to upgrade is to improve performance, gain additional memory, or enjoy built-in wireless capabilities.

Raspberry Pi 2

While the Plus and prior boards all used the same BCM2835 SoC, the Raspberry Pi 2 (see Figure 1-4) was the first to feature a brand new processor: the BCM2836 SoC. Featuring four processor cores to the original's lone core, the BCM2836 offers anything between four and eight times the performance of its predecessor—making everything from word processing to compiling code run faster. The board also boasts 1 GB (1024 MB) of RAM, double the maximum previously available, making multitasking and memory-intensive applications smoother and more responsive.

Layout-wise, however, little has changed from the Model B+. The Raspberry Pi 2 features the same 40-pin GPIO header, four USB ports, 10/100 wired network port, and all other ports. If you have a case or add-on device which works with a Model B+, it will also work just fine with the Raspberry Pi 2—but may run considerably faster!

The Raspberry Pi 2 boasts wider software compatibility than its predecessors: as well as Raspbian, the recommended Raspberry Pi operating system, the Pi 2 can run operating systems such as Ubuntu and Windows 10 IoT Core not available for the older models.