Xonard: a simple daemon to handle the non standard audio controls on Asus Xonar U1 devices
Copyright 2012-2013 Alessandro Pignotti

Asus Xonar U1 are pretty nice USB audio devices with a decent audio quality and a knob to control the volume and mute status of the device. The audio device itself is completely supported by linux using the snd-usb-audio kernel module. The control interface identifies itself as a standard HID devices, unfortunately this seems to be not actually true.

Xonard will configure the device to properly deliver interrupts when the knob is used using the hidraw kernel interface and deliver the events to the system using the uinput kernel interface. As an added bonus the blue LED blinking is set to something reasonable.

I've also reverse engineered how to configure the blinking of both the blue and red LEDs and the code should be pretty self explanatory about how to use this functionality. But this is not currently used beside setting a sane default

Disclaimer: The code should be pretty safe, but consider that it does not come from official documentation, since I've found none. Don't blame me if it does harm your device or your cat.