RTC not running in Stop Mode

chris239955_stm1_stmicro · ‎2014-08-05

Posted on August 05, 2014 at 14:58

Using an STM32F103, I want to wake from Stop mode by RTC alarm after 5 seconds.

I have set EXTI on UART_RX and #17 for RTC.

Here is what I know:

I can put the MCU into Stop mode (via WFI).
I can wake from Stop via UART_RX EXTI.
I can configure RTC for LSI, and it counts up in Run mode.
I see 5sec RTC alarm triggers EXTI_17 in Run mode.

However, when MCU is in Stop mode, it appears that the RTC counter doesn't advance at all. After Stop for 10sec, the RTC time is only 1sec later than when we entered Stop mode.

It seems I'm missing something like ''Enable RTC clock in Stop Mode''.

Can anyone give me a tip?

Best,

Chris

Tesla DeLorean · ‎2014-08-05

Posted on August 05, 2014 at 16:15

It seems I'm missing something like...

Like the LSI is in the wrong power domain, use the LSE

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chris239955_stm1_stmicro · ‎2014-08-05

Posted on August 05, 2014 at 16:16

I solved my issue by resetting the backup domain in my initialization code:

298 PWR->CR |= PWR_CR_DBP;

299 RCC->BDCR |= RCC_BDCR_BDRST;

300 RCC->BDCR &= ~(RCC_BDCR_BDRST);

And then wakeup from RTC works as expected.