Quote Originally Posted by mackrackit View Post
5 volts if the the chip is running on 5 volts and not changing the reference and using 8 bit resolution will equal 255...
Yes I know 5V = 255, but what I was getting at...until I set all the portC pullups disabled (which they should have been at power up anyway), in the absence of an incoming analogue signal, I was geting an ADC reading of 255 (because there was 5V residual on the unconnected pin)...soon as I disable pullups, I got the reading I was expecting ...ie an ADC reading of 0.