- a mp3-decoder chip
- a source selector & volume controller
- an interface to support many small-sized text/graphics lc-displays (plcdio-style)
- one or two radio tuner modules with hw rds/rdbs decoder
- 3 push-buttons and a rotary encoder + 4th button
- an ir-remote sensor
- additional mono and a stereo line-in
All of these devices are supported by linux drivers (mp3,mixer,radio/rds,buttons) or software packages (lirc, lcdproc)!
There is some older but more into depth documentation available.