What is ADC 2 there for on the pin out?
I was looking at the WiPy 2.0 pin out, and on the right half side, you have ADC1_0 (till 7) and on the left hand side you have ADC2. However, I cannot access the ADC 2 pins using this command "apin = adc.channel(pin='P20')", as it is an unavailable resource. I can only access pins linked to ADC1. My question is, what is ADC2 there for?
P20 is an ADC1 pin, are you sure you can't use it?
As for the ADC2 that is not currently supported in the Python side because it it's a bit of an oddball: due to hardware/firmware limitations you can't use WiFi and ADC2 at the same time. For now to use it you'd have to program in C and have WiFi off.