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Tamper Pin Output for RTC

Question asked by gt on Jul 25, 2013
Latest reply on Jul 25, 2013 by Clive One
I am using STM32VLDISCOVERY board (with STM32F100RB) to develop a basic real time clock application. Since I do not have a 32kHz crystal for now, I am using LSI clock instead of LSE.
When I debug the code, I can see RTC counter increments by 1 in each 1 sec, which means it should be working fine but when I try to get tamper pin output of RTC with the code below*, I get a square wave with 652Hz frequency instead of ~511Hz.


(By the way,  to get a proper 1 second time, I set prescalar value to 41942 but the frequency of the output from tamper pin does not change even if I make the prescaler value 32767.)