3-66 Theory of Operation: Bluetooth
The Bluetooth audio is sent over a two-channel PCM/SSI interface to the audio codec (U6405) on 
the Main board.
Table 3-17.  GPIO I/O
Signal Name Pad Name GPIO Keypad Board Schematic 
Name
I/O
GPIO41 PB09 41 BT_HOST_WAKEUP_3.3V I
GPIO49 PB17 49 BT_PTT_3.3V O
GPIO50 PB18 50 BT_SHUTDOWN_3.3V O
GPIO51 PB19 51 BT_WAKEUP_3.3V O