Sensor input mode measurements

[Mitch Bradley]

James Cameron wrote:
> That's great, Mitch.
>
> I can figure out a few uses for such an ADC ... based on hobby
> electronics practice.  Resistive and voltage generating sensors of
> suitable value would work immediately.  Other sensors might need a DC
> buffer stage to bring them into the voltage range.  The USB socket can
> provide 5V DC.  I look forward to testing.
>   
The MIC input itself looks like 3K to 2.3 volts (but you can turn that 
off, so that it looks like about 20K to ground).  With some cleverness, 
it might be possible to use that to power the buffering, or just us a 
bias pot that you have to calibrate.
> Suggestion: check the standard deviation of the 4000 samples, so that we
> could see the level of noise?
>   
In fact, I did check the min and max samples.  The noise was roughly +- 
8 counts.