USB AMR interface (using Audio Class)
=====================================

For the icebreaker, the USB hardware connections are :

  * `P1B4`: USB DP
  * `P1B3`: USB DN
  * `P1B2`: Pull up. Resistor of 1.5 kOhm to USB DP 

and the AMR connections are :

  * `P1A1`  : `AC97_RESET#`
  * `P1A7`  : `AC97_SDATA_OUT`
  * `P1A8`  : `AC97_SDATA_IN`
  * `P1A9`  : `AC97_SYNC`
  * `P1A10` : `AC97_BITCLK`
