Raspberry Pi AirPlay Speaker

The Raspberry Pi is quite a little device. Although not the first of its kind, it has exploded in popularity because it has combined very capable, full feature computer hardware in a tiny form factor at a unbelievable price ($25-35). It has a 700Mhz ARM CPU with 512 MB of RAM with all the standard connectors that you would expect to come on a computer like an analog audio out port, 2 USB ports, wired ethernet, and analog RCA and digital HDMI video out for connecting a monitor. In addition to that, it has a bank of GPIO (General Purpose Input/Output) pins for connecting to hardware. These can be used for anything from simply controlling a LED to a motor to reading from any number of different kinds of sensors.

There is also a SD Card reader onboard. There is no onboard memory on the Raspberry Pi so all files are kept on a SD Card. Think of it exactly like the hard drive in your computer.

The final component of interest onboard is the micro-USB port. This is not used for data or connecting to your computer but rather as the power for the Raspberry Pi. The Raspberry Pi used very little power and 5V that USB provides is enough to power it as long as you aren’t using any addition devices plugged into the Pi that use a lot of power.

Here is a quick start guide to help you get started if need to help hooking it up and powering it on.

Every computer needs an operating system (OS). Your Mac runs Mac OS X and your iPhone, iPad, etc run iOS. The OS handles all the interfacing to the hardware so that “apps” can just do what they need to do.

A Raspberry Pi can run many different OSs, but the one you’re going to use here is Raspbian. Raspbian is a version of the Debian Linux distribution dedicated to running on a Raspberry Pi. Therefore it’s perfect for this tutorial!

To get your Raspberry Pi up and running with Raspbian, you’ll first need to download and install it. This is done by downloading something called an “image”. An image is simply a snapshot of a pre-installed copy of Raspbian, ready to copy over onto your memory card to run on your Raspberry Pi.

Go here and look down the page for the Raw Images section. Under the Raspbian sub-section, download the image either as the direct ZIP or using the torrent. The torrent is downloaded using the bit torrent protocol. If you don’t know what that is just download the image directly.

The zip file contains a disk image (a .img file) of the entire installed operating system. Download and extract the image from the zip anywhere you have access to it. Then you are just going to copy the data in the disk image on the SD card (in the next section).

The default root (administrator) username and password are:
Username: pi Password: raspberry

Make a note of these, because they’ll come into play later.

In order to copy the image on the card, you’re going to have to use the terminal or command line. Though all the typing is a little intimating at first, in some ways it’s a more powerful interface that a standard GUI interface for some tasks. Don’t be afraid of it, the hardest part is just memorizing the commands but hey, that’s what this tutorial is here for!

Open a Terminal window. You can do this quickly by hitting Command+Space and typing terminal into Spotlight. Run the following command, without the memory card inserted:
df -h

As you can see, the df command shows the free space on each disk. Notice that the command also shows the address of each disk (e.g. /dev/disk0s2).

You’re going to use df to discover the address of your memory card. Insert the memory card now into either the memory card reader on your Mac or into a separate reader that’s connected to your Mac. Run the df –h command again, and you should see something like Image 1.

You should see a new disk, something like /dev/disk1s1, that matches the size of your memory card. The description of the new disk is the card’s address. Unmount the memory card’s disk with this command:
sudo diskutil unmount /dev/disk1s1

Next you need to get the device address. This is the address of you memory card “reader”. To do this, take the address you were using before, in my case /dev/disk1s1, remove the s1 portion from the end of it and add r in front of disk so that /dev/disk1s1 becomes /dev/rdisk1. The two addresses are different in that /dev/disk1s1 is the address where first file system partition is mounted. /dev/rdisk1 is the address of the memory card reader device (has nothing to do with the card that is inserted at the time).

You can now write the image file that you downloaded above onto the memory card. Run the following command:
sudo dd bs=5m if=~/Downloads/wheezy-raspbian.img of=/dev/YOURDISKNAME

This is where all the magic happens. You are using the dd command to copy an input stream byte-for-byte. You can’t use a standard drag-and-drop copy to move the files over since special formatting for system boot partitions are different and the Raspberry Pi wouldn’t know that it was a boot partition if you just dragged them over. Let’s take a look at each component of this command:

• bs specifies the block size that the dd tool uses. Specifying a larger block size helps copy the image faster.
• if specifies the input file. You point this to the image file you downloaded earlier.
• of specifies the output file. You set this to the disk name you came up with earlier, /dev/rdisk1.

Hit enter to run the command. It will take a few minutes to complete – use this time to start building that rocking playlist you’ll soon be streaming!

When the command is done running, you’ll see something similar to what is in the second image.

Now pop the memory card out of your computer and put it into the Raspberry Pi.

Plug in the Ethernet cable and then the micro-USB cable for power. Connect the other end of the ethernet cable to your router and the micro-USB cable into a computer or power adapter (like the one that comes with an iPhone or iPad).

Now how do you get access to the Raspberry Pi? In this tutorial, you are going to be setting up the Raspberry Pi computer without a monitor, keyboard or mouse. Instead you’re going to remotely log into it from your Mac.

SSH stand for Secure SHell and is a way to open a terminal session into a remote computer, letting you run a command just as if you were physically on that computer. This is convenient when you need to makes changes to a computer you don’t have physical access to, or, as in your case, one without a keyboard or monitor.

You’re going to be SSHing into the Raspberry Pi for a couple of reasons:

• Plugging in a mouse, keyboard, and monitor can add a large power drain that can lead to hardware failures and/or erratic behavior.
• SSH is a important and good skill to learn.

Before you can SSH into your Raspberry Pi, you need to figure out its IP address. This can be tricky, because by default it will use DHCP to automatically obtain an IP address. So you don’t know what it is. There’s a few ways to get the IP address, but I recommend you download an iPhone app called Fing that will do a network scan.

Download Fing and make sure your iPhone/iPad and the Raspberry Pi are on the same network. Run the app and you should see a list of all the devices on the network (see image).

Though I don’t recommend it, if you want to try connecting a monitor, keyboard and mouse to the Raspberry Pi, then you can use ifconfig, a Linux command, to list information about your network connections. If you do decide to go with route, connect a monitor and a keyboard and power it on. Once you’ve got your components connected and power on, you should be taken directly to a login where you should enter your username and password.

Once logged in, you should be left at a terminal command line and should be able to type ifconfig (image 3).

It is a little pointless to ssh in if you went through all the trouble to connect a keyboard, mouse, and monitor but it is still a good skill to learn.

Once you’ve obtained the IP address in one of these ways, you can SSH into the Raspberry Pi. Let’s say your IP address is 192.168.1.10. In the Terminal window, type:
ssh pi@192.168.1.10 // remember to replace with YOUR IP address
You’ll get what you can see in the first image.

Type yes and hit enter. Terminal will now ask you for a password, which by default is raspberry. Enter that password and you should be remotely logged into the Raspberry Pi and ready to go.

NOTE: If you can’t seem to find your Raspberry Pi on the network, then it might be because it is not booting properly. This can happen if you aren’t supplying enough power to the device. You can check for that by plugging in a monitor via HDMI. If it continually reboots, then power is likely the problem.

Now you need to expand the file system to take up the entire size of the SD card. You see, the image you loaded onto the SD card was of minimal size so that it would be quick to download and fit on all SD card sizes. Since we copied over the contents of the disk image onto the SD card, the partition size is the exact size of the disk image even though the size of your SD card might be bigger. But this leaves you with little space with which to work.

To set up the AirPlay receiver components and all the server components, you’re going to need more space. Luckily, it couldn’t be simpler to resize the partition to take advantage of the entire card. SSH back into your Raspberry Pi if you aren’t there already and run the following command:
sudo raspi-config

When the config menu comes up, select expand_rootfs.

You’ll then see the following (image 1), letting you know that the root partition has been resized.

When it asks if you want to reboot now, select Yes.

You’ll have to wait a minute or two and then SSH back in. You should now have plenty of space for the server components.

Now that you’re logged into the Raspberry Pi, you need to perform some basic setup. These include:

• Update the current system.
• Update the audio settings so sound comes out of the green, mini-jack port instead of the HDMI port.
• Install some needed libraries for the Shairport project.
• Install the Shairport project.
• Daemonize the Shairport project so that it start at startup

Let’s get cracking!

First you should update the current package sources and packages. This is kind of like running Windows Update or Software Update on OS X. With Raspbian, the tool apt-get handles all software packages for you.

Run the following two commands, one at a time:
sudo apt-get update
sudo apt-get upgrade

The first command, update, updates the list of packages and the versions. The second command, upgrade, compares that new information to all the packages you currently have installed and upgrades them if an upgrade is available.

You will probably notice quite a few packages being updated. Just sit tight!

By default, the audio comes out of the HDMI port on the Raspberry Pi. You want to change that to the mini-audio jack since pretty much anything that connects to audio can connect to a mini-audio jack and if you leave it set to HDMI, you’d probably have to have it hooked up to a TV all the time. Run the following command:
sudo amixer cset numid=3 1

You should see the results as shown in the image above.

The amixer command lets you view and set the options of sound cards. Here, you are setting the third soundcard element to 1, thereby activating the analog output for the Raspberry Pi. That might all sound magic, and, well, it is really. You just need to know that command. But fortunately I’ve found that out for you – that’s why you’re here!

The Shairport project you are going to be using has a number of prerequisites. Enter the following command to download and install these prerequisites using the same mechanism you used to update the system earlier:
sudo apt-get install git libao-dev libssl-dev libcrypt-openssl-rsa-perl libio-socket-inet6-perl libwww-perl avahi-utils libmodule-build-perl

This is a pretty long command but its actually pretty simple. Lets look at each individual part:

• sudo – Runs the next command in administrator mode
• apt-get – This the package manager program
• install – Tells the package manager program to install the following libraries
• git libao-dev libssl-dev libcrypt-openssl-rsa-perl libio-socket-inet6-perl libwww-perl avahi-utils libmodule-build-perl – These are the libraries we are installing. You can see there’s a couple here like git, some security/encryption libraries, and some libraries for the Perl programming language.

You’ll see what is shown in the image above.

It’s telling you what will be installed. This will include the libraries you asked specifically to be installed, and any prerequisites.

Since iOS 6, AirPlay has used the SDP protocol. The Perl Net-SDP project will help communicate using this protocol. So you’re now going to install it.

Run the following commands (still in your Raspberry Pi SSH session!):
git clone https://github.com/njh/perl-net-sdp.git perl-net-sdp

This clones the GitHub repository of Perl Net-SDP so that now you have a copy of it on your Raspberry Pi. You’ll get the following output shown in the first image.

Now enter the following commands, one line at a time:
cd perl-net-sdp
perl Build.PL
sudo ./Build
sudo ./Build test
sudo ./Build install
cd ..

These commands compile and install the components of Perl Net-SDP in the proper locations.

• You have reached the meat and potatoes of the project, the purpose of all of that setting up you just accomplished. Once you download and run Shairport, it’s only a few simple steps until you hear music!

Installing and Running Shairport

• Run these commands, which will clone the Shairport repository, then build the software:
  git clone https://github.com/hendrikw82/shairport.git
  cd shairport
  make
• Then run one last command to start the Shairport script:
  ./shairport.pl -a RayPi
• The -a command specifies the name of the AirPlay receiver, which in this case you are calling RayPi.

Now if you open any audio or music app on your iOS device or open iTunes on your Mac, you should see RayPi on the list of AirPlay devices!

When you’re done, hit Control+C to stop the process. You can change RayPi in the previous command to anything you want to call your AirPlay receiver.

As it stands right now, every time you want to use Shairport, you have to start up the Raspberry Pi, SSH into it and run the Shairport program. That sounds horrible to me. What can you do about it?

*Deep daemon voice* DAEMONIZE IT *End deep daemon voice*
*cough*

That sounds evil, doesn’t it? Actually, it’s quite the opposite – daemonizing will make your life much simpler.

So what is it? Daemons are tasks on Unix and Linux systems that run in the background and typically begin at system startup. It’s the perfect solution to your problem. You can create a daemonize the executable you just ran above so that it runs in the background and is started right at startup; that way you never have to worry about starting it up yourself.

SSH into the Raspberry Pi (if you aren’t still) and enter following commands to copy and configure the necessary files:
cd shairport
sudo make install
sudo cp shairport.init.sample /etc/init.d/shairport

This copies a sample init file to the daemon directory, the daemon directory was create by the ‘make install’ command.

Now enter these commands, one line at a time:
cd /etc/init.d
sudo chmod a+x shairport
sudo update-rc.d shairport defaults

Here you move to the daemon directory, change the permissions and then “install” the Shairport init file with the default options.

Now enter the following commands, one line at a time:
sudo vi shairport
DAEMON_ARGS="-w $PIDFILE -a RayPi"

You can use nano or any other text editor here if you’re more comfortable with that, but what you are doing is going into the Shairport config file and adding the -a RayPi part to the DAEMON_ARGS option. Just as when you trigger the script manually, you are modifying this to set the default name of the AirPlay receiver.

If you are using the vi text editor, hit escape, then type :wq and hit enter to save the changes. Now whenever you startup the Raspberry Pi, it will start the Shairport executable.