https://www.digikey.com/en/products/detail/texas-instruments/LM321LVIDCKR/9954206?so=82314272 found it, the values for the resistors were brute forced for what I needed, but honestly I think you could go without the opamp stuff, you just need to detect change so could probably get away with going straight into the ADC without the fanfare: https://chatgpt.com/share/6ac42244-7db4-83e8-b655-f67d46db6d1b check the code part out >>615161209 those are the best, keep in mind this was designed around the ~3v coming out of a CR2032, the transistor was used to turn off the hall effect sensor + opamp stuff from firmware, on/off "switch" is on PB0