Regarding POR(25)

[AshwiniKool]

Hi All

I am using STM32L053 board for a product development.

I am using RS485 communication Protocol. I am sending Data from Computer to the processor to get the response. 

When I send the data, I get proper response. but out of 10 times say 1 time the processor Resets with the error number 19,  that is POR(25)

This is reset due to CLASS B VAR FAIL. 

CLASS B VAR error comes as a result of 

Clock Status STL_Main Clock Test(void)  function which is written in the file STm32fxx_STLclockRun.c file.

this function has one condition,

 if (((PeriodValue ^ PeriodValueInv) == 0xFFFFFFFFuL)\
&& ((LSIPeriodFlag ^ LSIPeriodFlagInv) == 0xFFFFFFFFuL)\
&& (LSIPeriodFlag != 0u) ) 

in this condition, actually LSIPeriodFlag = 0  and also (LSIPeriodFlag ^ LSIPeriodFlagInv) are not exactly inverse of each other as LSIPeriodFlag = 0x00000000; LSIPeriodFlagInv = 0x55555555;

How to solve the problem?

Thanks in Advance

Regards

Ashwini

[Amel NASRI]

Hi @AshwiniKool ,

As you are using LSI as clock source, it is possible that you are facing similar issue as the one in STM32F4 MCU ST SelfTest Error(STL_MainClockTest).

Please refer to the answer from @Petr Sladecek there.

-Amel

[Petr Sladecek]

Hello,

if you inspect all available source files (stm32fxx_STLclockrun.c, stm32fxx_STLmain.c), you can find that during the library initialization and once the result of the clock measurement is checked, SW invalidates class B pair variable value by purpose via putting LSIPeriodFlag into zero. To repeat the clock test, SW then must wait next 8x LSI cycles at least to check result of a next clock cross check measurement cycle. Consistency of the flag (the variable pair) is renewed at TIM21_IRQHandler (stm32l0xx_it.c) raised by end of the measurement cycle when both its elements are set properly to signalize a new measurement result is ready to be checked:

/* Set Flag tested at main loop */
LSIPeriodFlag = 0xAAAAAAAAu;
LSIPeriodFlagInv = 0x55555555u;

Rgds,

Petr