Finally have audio capture working on beaglebone. The code requires a lot of cleaning up and optimization. Audio capture happens in realtime by programming one of the two PRUs (microcontrollers on the processor SoC).

Helpful links for getting this working:

1. pru-sdk
https://github.com/texane/pru_sdk

2. TI PRU Code Generation Tools
http://software-dl.ti.com/codegen/non-esd/downloads/download.htm#PRU

And some sample capture data.