I would like to pool external battery voltage status on ESP-201 (or any ESP8266). This is 2x1.5V battery but stepped up to 3.3V, so internal ADC is of no use.
As I know that it can read up to 1V on analogue pins, this is something that can be fixed with 220k/100k Ohm voltage divider to bring it down to desired level. Should this be connected to ADC pin or some other analogue pin?
As this should be low power circuit I would like to optimise the setup so that no power is spend when in deep sleep mode. Will this voltage divider burn battery, so that I would need to use transistor as a switch to switch battery reading on/off in order to minimise impact voltage divider?
Thanks,
DiNo