Non-Zero Voltage When Pin Isn't Connected to Anything

Hey so I’ve been using my Particle Photon for a little while now and I’ve been noticing this annoying issue recently. Whenever I power up my Photon, regardless of what program it’s running, it always sends out a voltage between 0.6-1V to all the pins so when I do an analogRead command (say though tinker) it reads a non-zero voltage. This voltage is confirmed via a multimeter. This issue seems to only cause a problem whenever the Photon is reading a zero or low voltage with a small current. I’m trying to read fairly low voltages (roughly around 0.16V) from some sensors. I know some other people I work with have also encountered the same issue with their Photon. Has anyone else seen this issue and managed to solve it? How does one manage to prevent this issue?


This is what's commonly known as a floating pin.
Floating pins will always drift. To counteract that you always need pull-resistors to ensure a valid signal state.

That with the way how the built-in ADCs work results in a wrong reading when the charge of the sampling caps is allowed to persist.

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