Expansion Ports CE & CSN

I successfully managed to use the ports CE (A0) and CSN (A1) as a 0-5V voltage meter. But there is a strange 1.2V reading on both ports without any cables connected and a strong effect where a voltage increase on one pin increases the readings on the other port too.

Everything works fine once I connect the CE & CSN pins to either GND or VCC, but it still leaves me puzzled about what is going on.

This pins are for the radio, and aren’t defined unless you’re ether using the radio library, or defining them yourself. What does your code look like? Are you setting the pins as analog in?

The voltage would ‘float’ of these pins also aren’t being ‘pulled’ in any direction, which is what you’re seeing. Don’t expect an accurate reading unless you’re actively applying some sort of voltage on them.