I am using an STM32F745VGT6 user board with Keil µVision 5. I want to use the internal RTC calendar with the internal clock (LSI).
My question is: first power on clock start 02:00:00 then time is going. For example, when time is 02:05:00 suddenly I power off the energy (cut off energy for Vdd, not for VBattery) then wait 10 minutes. After power on, the clock is still 02:05:00. I am stuck. It is so annoying.
I supply to uninterruptible 3.3 volt BIOS battery to STM 6.Pin (VBatt), as in the attached picture. If I remove the battery, each power off and power on start with 02:00:00. So I believe VBatt is working.
Best Answer
It's not going to work. From the Reference Manual
Unfortunately the LSI clock is not on the list, that's why it and the RTC stops when VDD is gone.