Photon analog input problem

[rickkas7]

It's unlikely to be a software issue on the Photon.

I use a circuit like this on my analog inputs:

Input protection tip

Sorry, I did not explain that well. Here’s a better example: I also have a pressure sensor that outputs 0 - 3.3V, so it does not need a voltage divider going into the ADC. In this case, I added a 100Ω series resistor between the sensor input (green line on the far right) and the TVS and ADC. [Screenshot 2023-02-13 at 05.45.05]

You add a 100Ω series resistor into the ADC, and a D1213A TVS which does two thiings: it protects against some ESD via the zener diode, and also protects against voltage above 3.3V or below 0V with the rail-to-rail diodes.

If the source is a voltage divider, you can skip the 100Ω series resistor (look farther up in that post).