In one test circuit I have a voltage (0 -1.6volts) going into the PIC ADC directly.. Although this works well, I suppose its safe practice to put a resistor (under 10K) in between as a precautionary measure... just incase that pin turns to being an output. I'm guessing any value that restricts current to under 20 mA is ok...as long as the sample times are adjusted...In this case the PIC is running at 3.3 Volts so the worst case is probably 3.3volts shorting to ground... anything over 165Ohms should be ok, right? I appreciate any insights/confirmation...