Noise now I have. Using a FEZ Domino I’m digitizing an audio signal from a microphone on AD0. When powered from USB the digitized signal is quite noisy with peak to peak noise spikes of several volts. If I switch the power to an external 9 volt supply the noise reduces to a reasonable level of about 100 millivolts p-p with one periodic spike around every 100 ms.
I will probably be able to live with this behavior as the real data collection will occur when the system is on external battery power, but I’d like to eliminate any noise that can reasonably reduced. Right now I have the other analog inputs floating. Should unused analog inputs be tied to ground or vcc? Any other best practices for reducing noise?
Thanks for any advice.