So this is interesting. I’m reading temperatures with two TMP sensors and a Photon. I was using analog pins A1 and A3. I noticed on one Photon that my readings from each TMP varied considerably (10 to 15 degrees F) even though the TMPs were on the same breadboard. A1 was reading correctly, A3 was reading low.
To troubleshoot, I switched the TMP sensors between each other. Same thing: A1 normal, A3 low. I then switched locations on the breadboard. Same result. Switched out all the wiring. Same result.
I then started moving each pair to various analog pins. Long story short, it appears there is something wrong with pin A1 but it results in an erroneous reading on the OTHER pin, not A1.
I emailed Sparkfun (it’s a Photon mounted on their Redboard) and they said this is a known problem. I can’t find any documentation about that and I also haven’t seen the same behavior on three of my other Photons.
Am I missing something?