Thanks for the info
A few thoughts:
EN for the ble module could be useful to shut it down as much as possible to lower the noise, or should we cut off its VCC in this case a p-chan mosfet on the VCC line could do.
If 2 batteries, then a boost converter could be used for charging them from the 5v. Boost converter is a mosfet, diode, coil, can be driven by the stm32 and monitored as well by the stm32 using an adc input.
Regards
Jose
Jose Luu