Comment 26 for bug 785939

Synthead: I saw your comment in IRC. You actually don't need to load a preset at all.
First give your user account write access to HID devices, see http://mixxx.org/wiki/doku.php/troubleshooting#mixxx_says_i_have_no_hid_controllers_attached_even_though_i_do
Then run Mixxx with --controllerDebug and just Enable the controller that appears.
Then, while watching the console, start moving knobs & pressing buttons and you should see hex dumps of the packets the device sends on the screen. This is where the detective work begins: you need to see which numbers change and how with each control. Note that some devices also send time stamps so a few bytes may always change even if you do nothing. Ignore these for now.
Let us know on mixxx-devel what you find and we can continue to help from there.