I'm sorry, I'm not sure I understood you.ahull wrote:You can of course get the STM core to shutdown completely before you reach the lower limit of the RTC retention voltage, and run the whole thing on one battery rather than having a separate supply for the RTC.
Currently I have a RTC module (DS3231) which has 3V button battery cell holder for retaining time, that I used with Pro Micro and tried using it with ESP8266.
I supposed that VBAT pin on STM32 board is only for RTC function of the board. Is this the case? Or is it used for other functions as well? I'm working on an aquarium controller, so I don't have the need battery powered STM32 board, I just need power for retaining time. Actually, I would prefer for the board not to do anything else but retain time when the power is disconnected.