RTC initialization faliure

[balazspeter93]

Posted on September 12, 2016 at 13:27

Hi,

I'm having a problem trying to initialize the RTC in an STM32L051K8T6 It's like I don't have access to the RTC registers. After writing 0xCA in WPR register I read it back and I get zero. I did everything according to the reference manual and what I found how other people implemented it. Do you have any idea what might go wrong? int main() {   RCC->APB2ENR |= RCC_APB2_USART1;   RCC->IOPENR |= RCC_IOP_GPIOA;     USARTConfig();     RCC->APB1ENR |= RCC_APB1_PWR; // Enable PWR clock   PWR->CR |= PWR_CR_DBP; // Allow access to BKP Domain     // Enable LSI   RCC->CSR |= RCC_CSR_LSION;   while(!(RCC->CSR & RCC_CSR_LSIRDY));   RCC->CSR |= RCC_CSR_RTCSEL; // Select RTC clock source   RCC->CSR |= RCC_CSR_RTCEN; // Enable RTC     RTC->WPR = 0xCA;   USARTSendHex(RTC->WPR); // I get 0x00 here   RTC->WPR = 0x53;   // Enter initialization mode   RTC->ISR |= RTC_ISR_INIT;   while(!(RTC->ISR & RTC_ISR_INITF));   // never gets here...     while(1)   {}   return 0; }

[stm32forum]

Posted on September 12, 2016 at 13:53

You need to read back trough the shadow register or set BYPSHAD (bypass shadow register) bit in the RTC_CR register.

[balazspeter93]

Posted on September 12, 2016 at 21:27

I found that I can not read WPR register cos it's always going to be zero according to the manual, however I don't fully understand what you're suggesting.

I can however read ISR register which has a value of 0x27 before and after trying to set the INIT flag. (I can't write it for some reason...)Any idea how this can happen?