Saturday, May 04, 2013

Adventures with the Raspberry Pi

Unless you've been under a rock for the last few months you can't have failed to have seen the Raspberry Pi; that credit-card sized ARM-based computer that sells for £25. Although it's modestly powered it does stand up as a small Linux computer for server, desktop or media-centre use. Remember; we had servers twenty years ago when no computer on Earth was this powerful!

So I've been monkeying around with a couple of these boards for a week or so and here are a few observations. To start with a few initial notes;
  • Make sure the SD card you use is both properly formatted and has a valid OS image on it; I battled with one board for days before re-formating it and sticking a new copy of Debian on it. The board literally looks dead if the boot-loader is corrupt.
  • I didn't find any of the problems a lot of online folks claim is an issue - power supplies; I've tried everything from iPhone, Kindle, no-name USB through to the USB-service port on the back of my TV. All powered the boards fine. I haven't measured it I imagine we're talking less than an amp at 5v.
  • It's a lot easier to us one of the many tools to format the card and copy on the OS image. I've been using RPi-sd card builder v1.1
So - there are numerous pre-compiled OS images for download and I suppose it depends on what you want to do with it. My first port of call was a Debian build called "Wheezy" which seems to be the general Linux distro of choice that comes with the KDE desktop. The card must be partitioned into a FAT32 formatted boot partition (64 megabytes) and the rest of the card (at least two gigs) as an ext4 Linux partition. YaST allows you to max-out the main partition when it runs. So long as you know what IP address gets assigned at boot-time you can SSH into the board;

So with Debian installed you can use it as a proper desktop machine or a network server. There are two USB2 ports and so it makes for a very powerful NAS head for a regular USB drive.

The other application that seems to attract the most attention is XMBC for which there are several builds. I stuck OpenElec onto another SD card (this is the joy - you can switch £5 SD cards around and you've got a new machine).

The XMBC builds don't come with a desktop or even an X-client (it writes straight into the display buffer - and it has MPEG2 & H.264 decoding on the board). But it is just the job for a Media Centre.
Another feature of the OpenElec build is support for the Apple Airplay protocol so you can "throw" media playback to it from iTunes or iPad/iPhone;

Several folks online have commented about the poor output quality of the analogue audio 3.5mm jack. The HDMI audio is fine and although the mini-jack ain't great I discovered a couple of things that improved it to tolerable;
  • Don't use a USB hub to power the Pi - most don't have a great regulation of the 5v rail which also tend to be noisy. A Kindle or Apple wall-wart suffices.
  • Use a good-quality USB cable; I had a cheapie cable powering the board and it covered the audio output in hiss. A Kindle cable did the job.  

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