ALSA Audio for the Raspberry Pi

I ordered a Raspberry Pi about the time it was announced last year. At the time, it was necessary to order it from the UK. As a result of SNAFUs, I didn’t receive it till the end of last summer. By then, I was deep into work requirements that gave me little personal time. No time for ham radio, for sure.

Just a few days ago, I got past the point of loading Raspbian onto an SD card and getting the device to boot. Although I have a general interest in the Pi, and had already been exploring applications with a similar device, the “Guru Plug”, I now have a specific application for the Pi.

My first application is an audio/radio application that is running on several of my computers, and is starting to monopolize hardware that I’d rather be using in other ways. So my first definite Pi project is to get that audio project running on the Pi, so I can offload my other, more valuable systems, and return them to their original purposes. The application requires ALSA audio on Debian/Ubuntu, and not too much processing power. The Pi seemed a good fit. So, once I got it up and running, the question was: Does it support ALSA, and if so, does it support the Debian audio tools enough that my project will run on it? I don’t have the definitive answer yet, but it’s looking good.

Yes, the Pi supports ALSA audio. However, the support is NOT done in hardware per se (that is, not as in most modern laptops). It’s partial emulation, and partially the bcm2835 chip used in the Pi for HDMI output. This requires a kernel module that, in the case of the Pi on the “official” Raspbian distro, is loaded at boot time by default.

For more technical discussion of this subject, please see this page on the WA2IAC wiki.