I'm doing a project using 4 equal boards (lolin32 lite clones - like image below)
Within other things I've done a voltage devider to check the battery level (and for that I'm using pin VP since I saw a lot of recomendations to do so).
The reason I've opened this topic is because depending on the board (which should be equal) I've getting different readings.
My first though was that it is Hardware issue or that I may have damaged something when soldered the pin headers... but not sure... I've changed the pin but no matter which one I use I get lower readings with one of the boards (using of course the same battery and voltage devider)
What are your thoughts and what could I do to try to troubleshot and fix this?
real battery voltage is at 4.20v and shows correctly in the other boards (+/- 0.05V differences) but in this one shows 4.00v... meaning that when extrapolating to % it says it is arround 80% instead of 100%
I'm not entirely familiar with the internals of the ESP32 processor but it seems to have the same kind of internal analog reference as the Arduino Uno: Quite stable but not very accurate. The internal reference is 1.1V +/- 10%. Since your outlier is reading about 5% low that may be explained by a natural variation in analog references. If that is the case you will need to calibrate your calculations for each processor.
On the UNO it's easy because it has an Aref pin which is connected to the internal reference when you select INTERNAL rather than DEFAULT. I don't know how you would measure the reference on an ESP32.
