Download from Wow! eBook <www.wowebook.com> For your convenience Apress has placed some of the front matter material after the index. Please use the Bookmarks and Contents at a Glance links to access them. Contents at a Glance About the Author ...............................................................................................................xiii About the Technical Reviewers .......................................................................................... xv Acknowledgments ............................................................................................................ xvii Introduction ....................................................................................................................... xix ■ Chapter 1: Hardware Overview ..........................................................................................1 ■ Chapter 2: Installing Fedora ............................................................................................17 ■ Chapter 3: A Simple Temperature Sensor ........................................................................37 ■ Chapter 4: Driving a Simple Character LCD .....................................................................61 ■ Chapter 5: Security Monitoring Device ............................................................................87 ■ Chapter 6: Cross Compile Environment .........................................................................105 ■ Chapter 7: Mini Media Center ........................................................................................125 ■ Chapter 8: Adding an RTC ..............................................................................................145 ■ Chapter 9: Serial Server ................................................................................................163 ■ Chapter 10: Controlling a Mains Device ........................................................................179 ■ Chapter 11: Other Operating Systems ...........................................................................201 Index .................................................................................................................................233 v 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. • 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. • A screwdriver. In Figure 1 you can see the basic tools you will need. xx ■ INTRODUCTION Figure 1. Collection of necessary tools For each project you may need different components or cables. I will address the needs of each project in its own chapter. If you can I would recommend buying better-quality tools. They will work well and last longer but remember that the skill of the operator does not come from the price tag of the tools. ■ Tip I like to have a bright light when I am doing my soldering work. I picked up a nice flexible neck light from IKEA that fits the bill perfectly but this is purely optional. Some small prototyping boards may be of use as well or you can use PCBs that are made by hand or premade: it’s up to you and I won’t dictate what is right or wrong. I prefer to use prototype boards. As you can see in Figure 2 I like to use breadboards that have a handy USB power source attached. xxi ■ INTRODUCTION Figure 2. A small breadboard with a USB power adapter DANGERS OF MAINS VOLTAGE Because this book contains a project that involves being close to mains AC power I will pay due diligence and talk about the dangers of mains voltage, even though we never touch AC mains power in this book! Let’s start off with a small story about myself and how I found this out the hard way.