STK1000/Audio, external DAC
From AVRFreaks Wiki
STK1000 have an external DAC with an integrated amplifier. The external DAC can be used to drive a headset or the on board speaker.
The output of the AT73C213 DAC can be connected to the stereo phones jack by changing the audio jumper settings. The on-board speaker is always connected to the amplifier. The output of this speaker is also connected to the 2-pin connector JP7.
Block diagram
Interfaces
Refer the help files of the daughter board to find out what interfaces are used and which peripheral on the processor are connected to the interface.