This circuit is useful for scaling an audio input signal (from line or microphone) so that it can be input to the Critter Board. The goal is to scale an AC audio signal to a signal that moves from 0v to 3.3v, centered at 1.65v. The 50k pot on the first op-amp is a gain control. The second opamp also has a low-pass filter to help with aliasing by blocking higher frequencies. (a better design might provide a steeper rolloff at the Nyquist frequency, but this works pretty well.)
The circuit requires a single supply op-amp that can run on 3.3 volts. The opa234 from TI works well and is easily available (check digikey). We use the dual version.
Some software examples comming....
