Raspberry Pi Hacks Tips & Tools for Making Things with the Inexpensive Linux Computer

547 Pages·2014·13.1 MB·English

by  Ruth Suehle

Raspberry Pi Hacks
Ruth Suehle
Tom Callaway
DEDICATION
This book is dedicated to Seth Vidal. Seth didn’t live long enough to see
this book finished, but within it, a little piece of his hacker spirit will live on
forever.
Foreword
Eben Upton
Founder and Trustee, Raspberry Pi Foundation
In April 2011 I was coming to the end of an executive MBA program at
Cambridge and looking forward to spending some quality time with my
wife, Liz. The old joke is that MBA stands for married but absent, and
after two years of barely seeing each other, the last thing on our minds
was jumping straight into another startup.
But after our accidental announcement of the Raspberry Pi educational
computer project the following month (see “Funny Story...” sidebar), we
had little choice but to knuckle down and make it happen. Liz, a freelance
journalist by background, dropped everything to run our nascent
community at www.raspberrypi.org. I, along with my colleagues at
Broadcom and my fellow Raspberry Pi Foundation trustee Pete Lomas,
started to figure out how to actually deliver the $25 ARM/Linux box that
we’d so rashly promised to build.
FUNNY STORY…
We went to see Rory Cellan-Jones at the BBC, in the hope that we might be able to use the
dormant “BBC Micro” brand. He put a video of our prototype on his blog and got 600,000
YouTube views in two days. There’s nothing quite like accidentally promising over half a
million people that you’ll make them a $25 computer to focus the mind.
Nine months later, we launched the Model B Raspberry Pi, taking
100,000 orders on the first day and knocking out both our distributors’
websites for a period of several hours. In the 18 months since then,
we’ve sold nearly two million Raspberry Pis in over 80 countries.
So, how did our little educational computer, conceived as a way of getting
a few hundred more applicants to the Computer Science Tripos at
Cambridge, get so out of control? Without a doubt, the explosive growth
of the Pi community has been thanks to the creativity and enthusiasm of
hobbyists, who see the Pi as an easy way to connect sensors, actuators,
displays, and the network to build cool new things. Where for the first
year of the project Liz’s blog posts described work that was being done
by us as we struggled first to design the Pi and then to build enough of
them to keep up with demand, today the vast majority of her posts are
about what you have been doing with the Pi.
It’s hard to pick favorites from the vast number of projects that we’ve
seen and featured on the website. As an unreformed space cadet, the
ones that stand out most in my mind are Dave Akerman’s high-altitude
ballooning and Cristos Vasilas’s astrophotography experiments. Dave’s
work in particular promises to put a space program within the budgetary
reach of every primary school in the developed world and is part of a
broader trend toward using the Pi to teach young people not just about
computer programming, but about the whole range of STEM (science,
technology, engineering, and mathematics) subjects. Another great
development in this area was Mojang’s decision at the end of 2012 to
port Minecraft to the Pi, creating the scriptable Minecraft Pi Edition and
spawning a large range of educational software projects.
As we head into 2014 and toward the second anniversary of the launch,
we’re looking forward to seeing what you all get up to with the Pi. One
thing is certain: it won’t be anything I can imagine today.
Preface
The inspiration for the Raspberry Pi was born when Eben Upton was
working with computer science students at Cambridge University (see the
Foreword for his own account). He saw a need for incoming students to
have greater opportunities to obtain programming experience before they
got to the university level. The first concept designs for what would
become the Pi we know now were born in 2006. Alpha boards were
demonstrated in late 2011, and the first 10 boards were auctioned off at
the beginning of 2012, raising £16,000.
The first batch of 10,000 Raspberry Pis went on sale February 29, 2012.
Toward the end of 2011, the SD card image for it had already been
downloaded more than 50,000 times, hinting at its impending popularity.
The two UK sellers at the time, Premier Farnell and RS Components,
sold out within minutes, with the latter reporting more than 100,000
orders that day. Upton designed them for education—specifically Python,
hence the “Pi” part of the name. But the tiny board caught the eye of
already-experienced programmers and electronics hackers. As of this
writing, a year and a half after that first day of sale, more than two million
have been sold.
And then roughly 1.95 million of them got stuck in an office drawer while
their owners gathered with hackerspace friends over beer and collectively
lamented, “Yeah, I bought a Pi, but I haven’t figured out what to do with it
yet. I was thinking I might use it to build a time machine and try to study
the K-Pg event in person, but I’ll probably just put XBMC on it.”
We wrote this book for you, the ones who haven’t decided what to do
with your languishing Pis yet. Of course, if you do just want to install
XBMC, you can refer to [Hack #54] and then read the rest of the book to
see the fun you’re missing. Alas, we haven’t perfected the time machine
hack yet, but follow @suehle and @spotrh on Twitter, and we’ll let you
know if we find a good source for flux capacitors.
We’re in what we hope is still the early stages of a return to a DIY culture.
Those of you deeply embroiled in it already, who have been to every
Maker Faire and joined your local hackerspace the day it opened, might
insist that, on the contrary, we are deep in the midst of said return. But it
hasn’t gone far enough yet. Beyond our little maker/hacker/builder/doer
niche is still a wide world of disposable goods and electronics
consumption and dump-tion. Our devices are increasingly designed to do
what the designer intended without the flexibility to do what the owner
intends, needs, or wants. Further, they often are sealed up boxes,
keeping prying fingers from ripping them apart and rebuilding them to suit
new visions.
The acceptance of closed, unhackable, unfixable goods is relatively new
in the course of human culture. It’s not so long ago—perhaps even your
own childhood if you’re over 30 or so—in which we were happily building
our computers from kits and taking the TV to the repair shop instead of
buying a new one. Devices like the Raspberry Pi help bring us back to
that better time when we knew (or could find out) what was happening
inside the things that we owned, when we could change them for the
better and give them new life when they broke down.
The first chapter of this book is for everyone with a Raspberry Pi; it gives
you a basis on which to build all of the hacks. From there, we move on to
the larger projects that implement all of those smaller hack needs. And in
the spirit of the Pi’s original purpose, we hope you learn a lot.
Who This Book Is For
Despite the potentially intimdating word “hacks” in the title, we don’t
expect you to be a Linux kernel developer or electrical engineer to be
able to use this book. Hacks and hacking—not in the sense you hear
those words used on the six o’clock news—are how many of us learn
best. Hands on, trying something new, possibly frying electronics in the
process.
We’ve tried to write these hacks so that even the novice can follow along
and become a Raspberry Pi hacker. It will help greatly if you have at least
a rudimentary understanding of how to use the Linux command line. For
the most part, we walk you through those steps, too, but in places where
we haven’t, a quick look to Google or to the man pages of a command
should catch you up.
As to the electronics half of the hacking, we’ve tried to spell as much out
in detail as possible. For those who already have a workroom filled with
jumper wires and strange parts you picked up out of the electronics store
clearance bin “because they might be handy someday,” this level of detail
might feel belabored. Just skip ahead to the parts that are useful to you
and be thankful that your less-knowledgeable friends will be getting help
from the book instead of calling you to ask if “GND” is really that
important, based on the assumption that it’s an amusing nod to their
childhood and stands for “Goonies Never (say) Die.”
How to Use This Book
Although you can read this book cover to cover, each hack should stand
alone, so feel free to browse and jump to the different sections that
interest you most. If there’s a prerequisite you need to know about, a
cross-reference will guide you to the right hack.
The hacks in the book are organized into the following chapters:
Chapter 1, Configuration Hacks
The first chapter introduces you to the common needs of Raspberry
Pi users, like making sure you have the right SD card for the project. It
deals with the assorted parts and issues you’re likely to encounter
with any Raspberry Pi project, such as power problems and getting
aquainted with the GPIO pins. You’ll also find tips and tricks for
dealing with some of its more finicky aspects.
Chapter 2, Hacking Linux for the Raspberry Pi
The most basic description you can give of the Raspberry Pi is “small
Linux computer,” which means a lot of the things you’ll want to do will
require some knowledge of Linux, working from the command line,
and getting into the system. Even if you’re relatively new to Linux,
we’ll help you walk through processes—like building a custom kernel
and updating the firmware—that might sound challenging to the
novice but don’t have to be.
Chapter 3, Raspberry Pi Around the House
Now that you’ve gotten the hardware and operating system under
control, you can start looking for bigger projects. In this chapter, you’ll
find some ways to use it around the house, including in really useful
projects that make your home computing setup a little smoother.
Chapter 4, Hacking the Outdoors
Why should all the Pi fun be inside your house? You can use it to help
out in the garden, take it geocaching, or run an animated holiday
lights display from it. And that’s just the beginning. What if you could
(nearly) waterproof it?
Chapter 5, Multimedia Hacks
Back inside (mostly), this chapter presents the many ways you can
use your Pi for entertainment. You can play music in a few ways,
including by turning the Pi itself into an FM radio or by using it to set
up a home theater. Then you can take it on the road and let the kids
watch movies from the backseat by integrating a touchscreen.
Chapter 6, Extend Your Pi
This final chapter addresses some larger projects (not that launching
an aerial photography rig isn’t big!). Use the hacks in this chapter to
attach more things to your Pi, get more control over the GPIO, and
even build your own cluster of Raspberry Pis with up to 64 nodes.
Hardware Requirements
Most of the hacks in this book use the Raspberry Pi Model B, version 2.
Here is a little information for you to consult and compare to the needs of
your intended project before deciding whether the board you have will
serve your purpose.
WHY “MODEL A” AND “MODEL B”?
In keeping with the educational goals, these names are a nod to the inspiration for the
Raspberry Pi, the BBC Micro computer released with the same model names in 1981.
The Broadcom BCM2835 chip, 700 MHz CPU, and GPU are the same
across the boards. All of them offer HDMI, composite RAC (PAL and
NTSC), and a 3.5 mm audio jack. They all also have the same SD card
slot. The Model A sells for $25, while the Model B sells for $35. See
Table 1 for a description of notable differences.
Table 1. Differences between Model A and Model B
Feature Model A Model B
Memory 256 MB SDRAM 512 MB SDRAM
USB ports 1 2
Ethernet none 10/100 Ehternet RJ45
There are also two revisions of the Model B board, as shown in Figure 1.