Practical Raspberry Pi.pdf

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Contents at a Glance

About the Author �� xiii

About the Technical Reviewers �� xv

Acknowledgments �� xvii

Introduction �� xix

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Chapter 1: Hardware Overview

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Chapter 2: Installing Fedora

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Chapter 3: A Simple Temperature Sensor

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Chapter 4: Driving a Simple Character LCD

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Chapter 5: Security Monitoring Device

�� 87

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Chapter 6: Cross Compile Environment

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Chapter 7: Mini Media Center

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Chapter 8: Adding an RTC

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Chapter 9: Serial Server

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Chapter 10: Controlling a Mains Device

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Chapter 11: Other Operating Systems

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Index�� 233

Introduction

Practical Raspberry Pi sounds more like a math book than something you voluntarily pick up to read for fun. Luckily

for you, there will not be much math content and it will be fun. So what is Practical Raspberry Pi all about? It’s about

simple day-to-day projects — ones that are fun, functional, and for everyone to do — for your Raspberry Pi.

I would hope that you would have some idea of Linux; any distribution is okay and I will cover a few different

operating systems in this book anyway. If you feel a little uncomfortable with Linux or the Raspberry Pi is your first

Linux machine, I urge you to read over Peter Membrey’s Learn Raspberry Pi with Linux . I also hope you can tell the

hot end of a soldering iron from the cold end, even though you don’t need to be a soldering expert for the projects

in this book. By now you should have at least one operating system installed on your Pi; if you don’t, not to worry

because it will be one of your first tasks in this book.

So what makes the Pi something you hunger for? Everyone loves cheap hardware and I love all hardware, no

matter how old or obscure. The Pi is a very capable little machine; also for hardware projects, it’s not bad! You could

get more on the hardware side out of an Arduino but the Pi offers something more than just hardware. It’s not just one

slice of the computing world: it’s the whole pi. From hardware-level projects to software-level projects you have it all

in front of you with the Pi. So you have a world of opportunities. For example, you could carry around the Pi with you

or set it up inside your house as an IP-enabled power switch.

I have always liked to pull electronic things apart to see what’s inside them and how they work. Collecting

assorted chips and other electronic junk seemed second nature to me; I had always pined for a computer of any sort

as a child and when I finally did get one I just wanted to pull the case off it!

Well, the Pi comes with no case so that’s not much of an issue. Even without a case to remove it’s a very exciting

piece of hardware. Finally we have a cheap solution that can bridge the hardware and software gap that will take

advantage of Linux. Given the Pi’s price, I hope you feel more willing to experiment with the software and hardware.

Given this, I want to talk about how to approach the hardware and not feel worried about it. Don’t feel upset or

annoyed when things don’t work out. Hardware has a tendency not to work for the smallest reasons. You might have

had a bad solder joint or soldered something in backward. You may think it sounds so silly, but it’s often the smallest

things that trip you up.

Here’s some personal experience to illustrate this point. Living in Hong Kong gives me access to cheap electronics

and I’ve always wanted a Hakko soldering iron but back in Australia they are very expensive as they need to be

imported from Japan. So recently I became the proud owner of a nice Hakko station and on that particular day

I brought it home, unboxed it, and smiled at its majesty. I plugged it into the wall and broke out a test printed circuit

board (PCB) I had lying around and waited for the unit to heat up.

After some time I noticed it was not heating up. I tried everything to make it work: changing fuses and double

checking everything, or so I thought. It was only when my wife walks in and asks why it was turned off that I glance

down at the small power switch on the unit to notice it was off.

Sometimes it’s so simple you miss it!

Take a step back and relax: your Pi will be fine. Most of the time things don’t work for me the first time; in fact I

cannot recall when they ever do. This used to get on my nerves a lot and I would end up sitting there forcing myself to

sort it out. I now know this is the wrong approach with electronics: you will make mistakes and you will let the magic

smoke out!

xix

■ IntroduCtIon

WHAT IS THIS MAGIC SMOKE?

the magic smoke is an inside joke in the electronics field. supposedly there is a magic smoke that lives in all

electronics components and that makes them work. so if you were to let the magic smoke out of the component,

it would no longer work. In short, you blew it up. some larger integrated circuit devices do in fact let out a small

puff of blue smoke if you blow them up. thus, the magic smoke story was born.

Just take a step back and go over the basics and you will find your problem. Now that you feel more relaxed, let’s

talk about the tools you will need to work with for the projects in this book. You will already have a Raspberry Pi in

your hands and for a lot of the below projects you will need the Model B.

Basic Tools

You should already have an SD card by now. Unfortunately you cannot net boot the Pi! I would suggest you get a few

different SD cards: one 32-GB card for the main work and some 16-GB or 8-GB cards for the smaller project work.

Separation will make it less confusing when you swap between operating systems.

I would also assume you have a power supply of some sort but if you don’t have one, go and grab any wall plug

that has a micro USB plug on it. There are a lot of phones that have this. Don’t try and power it from your desktop

or laptop if you have the Model B as it requires up to 700 mA and your USB bus maxes out at 100 mA unless the USB

device negotiates for more power (which the Pi does not).

You will also need these basic tools:

•

A set of small cutters and pliers.

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A half-decent multimeter (no need to go over the top on the multimeter). Personally you

should aim for a meter that can measure voltage, current, and resistance down to at least two

decimal places; I like meters that come with a stand but that’s a personal preference.

•

A soldering iron. You should be able to get away with a basic iron. A small hand iron with a

normal tip will be fine. I never had the luxury of a good iron until recently. The tools are not

100% of the end result; your skill will play a large part. Take good care of the soldering tip and

use it correctly and you will be fine. Clean your tip with some steel wool made for soldering

irons rather than a wet cloth and the tip will last longer.

•

Some solder. Do keep in mind that lead-free solder is harder to work with and melts at a

higher temperature but is better for the environment.

•

A desoldering wick.

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A screwdriver.

In Figure 1 you can see the basic tools you will need.

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