I'm looking for a small stm32f4 developement board (even smaller than the stm32 blue pill) and found the espruino pico looking very promising.
But one of the requirements I have is to be able to enter VBAT mode and use the internal RTC calendar with low speed external clock (LSE). I have found that the pico supports run, sleep and stop mode (and standby mode if I code it myself) but nothing about vbat mode. To enter vbat mode on a stm32 the VDD must be powered off and VBAT powered on, I thought vbat mode was supported when I saw the vbat pins on the board but it seems like it is just for powering the board instead of USB. Is it possible to do some easy fix so I can enter vbat mode and use the internal RTC calendar?
I have read that i must solder on a crystal myself and maybe two capacitors for the LSE or use the espruino wifi board which has it soldered on from production.
Thanks in advance!