STM32F207 does not wake up from STOP mode with RTC using LSI

ROBERTO ARRIBAS · ‎2013-09-03

Posted on September 03, 2013 at 17:15

Hi, i'm working with a STM32F207VGT and i dont achieve to wake up my board from STOP mode with the RTC. The RTC is configured with the LSI because the external crystal for LSE is not mounted.

I have read another post where it says ''

The RTC however does have a dependency on the VBAT supply, and only LSE is in the backup power domain (F1/F2/F4). LSI will not tick when the primary regulators turn off.

'' This could be the reason, but on the STM32 reference manual says that the IWDG works with the LSI, and the board wakes up from STOP mode due to the watchdog (it really resets), so LSI should be working.

Any idea why the RTC using LSI is not working?

Thanks in advance

Tesla DeLorean · ‎2013-09-03

Posted on September 03, 2013 at 18:44

I suspect it is gated.

Does the RTC keep ticking if you kick the IWDG, rather than let it reset?

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ROBERTO ARRIBAS · ‎2013-09-04

Posted on September 04, 2013 at 11:09

Well, I have tried the RTC/RTC_LSI example in order to know if the RTC is really working and I get blocked in the instruction ''

while

(CaptureNumber != 2){}''

, where CaptureNumber should be incremented with each TIM5 interrupt, but it doesn't (remains 0). TIM5 is connected to LSI (

TIM_RemapConfig(TIM5, TIM5_LSI);),

so I think LSI is not working.

How can I test if LSI is really ticking?

I suspect it is gated.

Does the RTC keep ticking if you kick the IWDG, rather than let it reset?

Tesla DeLorean · ‎2013-09-04

Posted on September 04, 2013 at 13:53

RCC_GetFlagStatus(RCC_FLAG_LSIRDY)

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ROBERTO ARRIBAS · ‎2013-09-04

Posted on September 04, 2013 at 16:57

Thanks clive1 for your reply.

Finally it is working and i'm not really sure where the problem was.

I suppose it could be:

- After changing RTC clock from LSE to LSI, a reset of the domain power must be performed (although i can assure i did it in some of my several tries)

- The RTC_WKUP_IRQHandler was not placed in the stm32f2xx_it.c file and thus, the ITPendingBit was not cleared...

But as said, i am not sure about the reason. Thanks!