Loopdeck Embedded Linux System

Electronic Setup

After jamming with a friend’s Boss RC-20 I decided to integrate live looping in my setup. Since I haven’t found any device that completely suits my needs as a drummer, I started to build my own looper device: the Loopdeck. It’s a portable device that fits into a 19″ rack and runs a minimal Linux system with Jesse Chappell’s excellent SooperLooper software. I can control two syncronized stereo loops via MIDI, e.g. using my drumsticks on the trigger pad and get visual feedback on the MIDI controller (a FaderFox LV2). See also my post containing the MIDI signal flow.

The device is built into a rack-mountable 19″ MiniITX case and bases on the Intel D945GCLF2 Mainboard with an Intel Atom 330 Processor (2 Cores, 1.6 GHz). The system boots from a 16GB Kingston SSD hard drive, MIDI and audio in/out is provided by an M-Audio Delta 1010LT PCI card. There is no screen or input device attached.

Loopdeck Signal Flow

Loopdeck interior

The system runs a customized Debian Linux (6.0 squeeze) with a minimal 2.6.33.9-rt31 realtime kernel and boots from a read-only partition on the SSD in under 10 secs. All services are automatically started and supervised (e.g. restarted on failure) by daemontools. These include the JACK audio server for low-latency audio, SooperLooper with two stereo loops, the nice JackTube for audio processing and the FluidSynth software synthesizer which I use to play piano, Rhodes and Wurlitzer soundfonts. Everything is connected using JACK and a self-written Python script which converts incoming MIDI message to OSC signals, provides MIDI feedback for loop and system states and even controls some light modules connected via USB serial port. More on this later…

• SooperLooper Live Looping Sampler: essej.net/sooperlooper/
• List of applications using JACK: jackaudio.org/applications/
• The Real-Time Linux WIKI: rt.wiki.kernel.org