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stm32g030 RTC/LSI ticks 50% too often

RRIDDICC
Associate II

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.

1 ACCEPTED SOLUTION

Accepted Solutions

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:

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4 REPLIES 4

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

JW

RRIDDICC
Associate II

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?

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:

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

JW