The new usb driver in darwinfox solved the previous issues with USB-Audio. Thank you Claudio for adding this! Darwinfox rocks!
These are the steps needed: 1. I added 'source "sound/Kconfig"' to openwrt/build_dir/linux-etrax/linux-2.6.25.16/arch/cris/Kconfig as Claudio suggested.
2. I selected usb-audio and alsa-utils in menuconfig. built and loaded fw into Foxboard. 3. I added group audio on Foxboard by writing: echo "audio:x:4242:" >> /etc/group 4. Now it works to play wav with: aplay -t wav /usr/share/sounds/alsa/Front_Left.wav You may want to check alsamixer also.
The foxboard is a little bit to slow for decoding high quality mp3:s using madplay. Maybe there are other players. I'm planning on streaming to Foxboard. That should work ok.
It would be nice to have Darwinfox patched to fix the Kconfig. (step 1)