please see this thread on the paths in the file system used to read encoder/button data -
the DAC and ADCs on the SSP together create a sound card with ALSA compatibility which you can open using any audio application. The following combinations of sample rate and buffer size are known to work but others might work just as well -
Regarding using the I2C port on the expansion connectors on the back of the SSP - the connector you need is the top right one. Below you can see the pinout of the connector with the SDA, SCL, GND and VCCA (+3.3V) nets highlighted.
However this I2C port is not enabled in the current device tree. When I do the next OS update where I add multichannel audio streaming over the USB device port I’ll enable the port so you can use it.
There is no support in our application to use this port, but of course you are welcome to build your own software or run whatever you want on the SSP and use this port. There is info on the web on how to access I2C ports in linux and how to use them.
Hope this helps. Let me know if you have any specific questions.