stm32g030 RTC/LSI ticks 50% too often

[RRIDDICC]

Hi!

I use the RTC of a STM32G030K6T. It is clocked by LSI (appr. 32kHz). And PREDIV_A is 0x0 and PREDIV_S is 0x7FFF. So I expect that RTC_SSR overflows every 1.024sec...

But: It overflows every 0.687sec... As if the LSI frequency would be 47712Hz...

I mentioned this after I soldered the positive contact of a LiFePO4 battery... Now I cannot easily disconnect power... Triggering the reset pin does not change the fast RTC... A software reset does not help, too...

How could I possibly damage the LSI by making a solder joint at the other side of the board? I even have a voltage clamp at 3.5V and a LDO (3.0V) between that solder joint and the STM32G030.

Or is it more likely that I made some last minute firmware changes? What could that be?

Thx.

Bye.

[waclawek.jan]

LSI can be output to one of MCO or LSCO pins, and its frequency measured there.

JW

[RRIDDICC]

after a power cycle (after some soldering under the hood... this time i turned off the soldering iron shortly before touching the board...) the LSI ticks at appr. 31765Hz again... giggle

what might be the reason?

[RRIDDICC · Accepted solution]

oh... ok... that would examine if the LSI is funny...

but: after a power cycle everything is back to normal... :grinning_face:

i think the LSI was puzzled by several power glitches during my soldering... it was quite wild... with a lot of sudden power interruptions... i have heard that power glitches can be used to get the firmware out of some Apple devices... :face_savoring_food:

[waclawek.jan]

Maybe this is an instance of the Unstable LSI when it clocks RTC or CSS on LSE erratum.

JW