The wm9711(g) is the onboard audio chip made by Wolfsonmicro.
The datasheet for the WM9711
- AC’97 Rev 2.2 compatible stereo codec
- DAC SNR 94dB, THD –87dB
- ADC SNR 92dB, THD –87dB
- Variable Rate Audio, supports all WinCE sample rates
- Tone Control, Bass Boost and 3D Enhancement
- On-chip 45mW headphone driver
- On-chip 400mW mono speaker driver
- Stereo, mono or differential microphone input
- Automatic Level Control (ALC)
- Auxiliary mono DAC (ring tone or DC level generation)
- Seamless interface to wireless chipset
- Up to 5 GPIO pins
- 2 comparator inputs for battery monitoring
- 1.8V to 3.6V supplies
- 7x7mm QFN or 48-pin TQFP package options
These are taken from the manufacturers webpage WM9711
This information is uncertain since the reference is to the WM9711L, while WM9711G is the chip on the GP2X. No information concearning the G model is found on their webpage.
There might be a possibilitie to connect a microphone to the chip, and by changing some registers in the wm9711, one could possibly get the mic signal to a ADC and read the converted information. I also have a phone input, pcbeep input and a line input.