Update on running Pd on the Raspberry Pi

Despite the initial excitement, running Pure Data in a dependable way with a USB soundcard has proved difficult. There is still hope though, and I wanted to share some of the information I recently gathered from Pd users on the pd-list. This is just a short post listing things that work (Linux distributions and soundcards), and stuff worth trying.

New distributions

Raspbian is nice for a lot of things, like learning programming, taking pictures now that the camera is out, and so on, but it hasn’t been optimized for audio work. And the USB is kind of broken in the sense that it is still very difficult to get sound interfaces that work in Linux to work in Raspbian.

Two recent distros are now available, though :

– Satellite CCRMA : build by the same team that makes Planet CCRMA (a very nice set of audio-oriented packages for Fedora, optimized for real-time work). I’m assumiong that it is based on Pidora (a Fedora version for the Raspberry Pi). Some Pd users have reported better results with soundcards with it. It is also worth mentioning that it comes with pd-extended (for some reason I could never get in to run in a stable way in Raspbian).

– Pd-L2Ork : a sort of fork of pd-extended build for the Linux Laptop Orchestra at Virginia Tech, which has been around for a while for Linux, and which recently became available for the Pi. I haven’t tried it yet myself, but apparently it has an improved GUI (useless if you want to run the Pi headless, but still…), and also offers interesting things for interfacing with the GPIO (including PWM and interfacing with analog converters). The later feature seems particularly interesting in that it could allow me to get rid of the Arduino I use to control my patch (if you don’t know what the GPIO is, here’s a quite thorough page about it. It’s just the pins that stick out of the RPi, to which you can connect push buttons for instance to interact with your Pi).

I should also mentioned Miller Puckette’s Raspbian image with an optimized version of Pd Vanilla. It also comes with the first version of the GPIO object. Again, I haven’t tried it yet.

Sound interfaces

As I said before, the biggest problem with the RPi at the moment is that soundcards don’t work as expected a lot of time, even those which work fine on other Linux platforms. Apparently there is a problem with how USB is handled on the Pi, and it hasn’t been fixed yet to my knowledge.

Here’s a short list of soundcards that have been reported to work on the Raspberry Pi :

• E-MU 0404 USB : that’s the one I own. Works with Pd on Raspbian without having to tweek anything.
• Behringer UCG102 : reported to work fine with Satellite CCRMA at 44100 Hz.
• Griffin iMic : reported to work on Raspbian (but USB speed needs to be slowed down by adding “dwc_otg.speed=1” to /boot/cmdline.txt).

Other promising platforms

This is a bit off-topic, but there seem to be good results with Pd (and “normal” soundcard behaviour) on the following two platforms :

• UDOO : a small computer running Linux like the RPi. It’s a bit more expensive, but it has onboard audio in and out (could be useful if you don’t need top sound quality), and includes the chip used on the Arduino Due (this means many ins and outs to control your patch without an extra Arduino).
• BeagleBoneBlack : another platform on which good results have been reported. It doesn’t have onboard audio input and output, but it does have plenty of pins to interface with it.