Standby and wakeup by RTC

[kreyl]

stm32f205ve, chibios v2.5.1
Task is to enter Standby mode and wakeup once a second or so.
I used RTC wakeup example from testhal\STM32F4xx\RTC, namely RTC wakeup setup and func_sleep():

Code: Select all

  /* set wakeup */
  wakeupspec.wakeup = ((uint32_t)4) << 16; /* select 1 Hz clock source */
  wakeupspec.wakeup |= 9; /* set counter value to 9. Period will be 9+1 seconds. */
  rtcSetPeriodicWakeup_v2(&RTCD1, &wakeupspec);

  chSysLock();
  SCB->SCR |= SCB_SCR_SLEEPDEEP_Msk;
  PWR->CR |= (PWR_CR_PDDS | PWR_CR_LPDS | PWR_CR_CSBF | PWR_CR_CWUF);
  RTC->ISR &= ~(RTC_ISR_ALRBF | RTC_ISR_ALRAF | RTC_ISR_WUTF | RTC_ISR_TAMP1F |
                RTC_ISR_TSOVF | RTC_ISR_TSF);
  __WFI();

It works for first time only. I.e. after power up, CPU enters Standby, stays there 10 seconds, wakes, (does something), enters Standby - and does not wake up.
Power switch leads to repeat of the scenario.
I outputted RTC registers values, namely ISR:

After PowerOn: 000027
After RtcInit(): 000007
After Wakeup setup: 000027
After Standby-and-wakeup: 000423
After RtcInit(): 000403
After Wakeup setup: 000427

Obviously, WUTF flag remains set during Wakeup setup.
When I put string

Code: Select all

  RTC->ISR &= ~(RTC_ISR_ALRBF | RTC_ISR_ALRAF | RTC_ISR_WUTF | RTC_ISR_TAMP1F |
                RTC_ISR_TSOVF | RTC_ISR_TSF);

before

Code: Select all

rtcSetPeriodicWakeup_v2(&RTCD1, &wakeupspec);

it started to work of properly. Namely, CPU wakes every time when expected.
It seems that WUTF should be cleared before setting up wakeup, it is insufficient to clear WUTWF only.

[Giovanni]

Hi,

I never played with the wakeup modes, barthess could probably help you there. I know he was using that.

Giovanni

[barthess]

I will check it. Wakeups was checked by me only on STM32F1xx. Looks like I need to check it deeper on STM32F4xx too.

[barthess]

Probably there is some differences between STM32F4x and STM32F2x in RTC cell. On my F4x it works fine without clearing of WUTF before rtcSetPeriodicWakeup_v2(). I can not test it on F2x because have no one board with it.