I am having trouble getting the RTC to work with battery backup. I am using LSE as the clock and I have enabled the backup domain. I can set the date/time values as expected.

[BBert]

 But when I remove power (with the 3V battery still connected to Vbat) the date/time values freeze. That is, they remain where they were when to power was removed. How do I make the RTC continue to run during power down? Any help is appreciated.

[AScha.3]

Hello Bert,

maybe LSE clock has not enough power -> set (in cube)  in RCC -> LSE clock setting : LSE drive -> high drive cap.

[BBert]

@AScha.3​  Thanks for the reply. I changed the LSE to high power but it did not help.

[AScha.3]

so.. have you some cap on this supply? i made 10uF cer. cap par to Vbat . shure , that your supply is okay? never seen this problem, if hardware ok.

we had problems with starting up, but all related to too low drive setting. otherwise it working fine.

maybe, you should read the AN about the LSE / oszillators .

https://www.st.com/resource/en/application_note/cd00221665-oscillator-design-guide-for-stm8afals-stm32-mcus-and-mpus-stmicroelectronics.pdf

[BBert · Accepted solution]

Problem SOLVED!

I disconnected the battery (with power off) from Vbat and then ran the code. I then reconnected the battery (with power off) and ran the code again. This fixed the problem. Apparently whatever state the RTC was in was being maintained by the battery so removing the battery solved the problem.