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[STM32L0] Wake up Flag for RTC does not rise when an alarm occurs

greffeb
Associate

‎2020-10-02 07:12 AM

Hi,

I have a STM32L071 on a custom board

The code was generated with CubeMx for TrueSTUDIO.

I have an alarm set on the RTC to wake up the chip from standby mode everyday at 2 AM.

I tested it and the system does wake up ! good.

My problem is that I need to differentiate the origin of the wake up between RTC alarm and WKUP pin 1.

I check for PWR_FLAG_WU which does not give much information to differentiate the two.

My understanding from the reference manual (RM0377 DocID025942 Rev 8 p559) is that the bit ALRAF in the RTC initialization and status register (RTC_ISR) is the one that might be useful for me.

But even tho the system wakes up from RTC, the ALRAF flag is not set

same with RTC_IT_ALRA and RTC_FLAG_WUTF

Is there a way to know if the origin of wake up is the WKUP pin ?

regards,

Benjamin GREFFE.

code used to check the flags : 

  if(__HAL_RTC_ALARM_GET_IT(&hrtc, RTC_IT_ALRA))
  {
	  lbWakedUpByRTC_IT = true;
  }
  if (__HAL_RTC_ALARM_GET_FLAG(&hrtc, RTC_FLAG_ALRAF))
  {
	  lbWakedUpByRTC_ALRAF = true;
  }
  if (__HAL_RTC_WAKEUPTIMER_GET_FLAG(&hrtc, RTC_FLAG_WUTF))
  {
	  lbWakedUpByRTC_WUTF = true;
  }

code to initialize the rtc

static void MX_RTC_Init(void)
{
  RTC_AlarmTypeDef sAlarm = {0};
 
  /** Initialize RTC Only 
  */
  hrtc.Instance = RTC;
  hrtc.Init.HourFormat = RTC_HOURFORMAT_24;
  hrtc.Init.AsynchPrediv = 125;
  hrtc.Init.SynchPrediv = 296;
  hrtc.Init.OutPut = RTC_OUTPUT_DISABLE;
  hrtc.Init.OutPutRemap = RTC_OUTPUT_REMAP_NONE;
  hrtc.Init.OutPutPolarity = RTC_OUTPUT_POLARITY_HIGH;
  hrtc.Init.OutPutType = RTC_OUTPUT_TYPE_OPENDRAIN;
  if (HAL_RTC_Init(&hrtc) != HAL_OK)
  {
    Error_Handler();
  }
 
  /** Enable the Alarm A
  */
  sAlarm.AlarmTime.Hours = 0x2;
  sAlarm.AlarmTime.Minutes = 0x0;
  sAlarm.AlarmTime.Seconds = 0x0;
  sAlarm.AlarmTime.SubSeconds = 0x0;
  sAlarm.AlarmTime.DayLightSaving = RTC_DAYLIGHTSAVING_NONE;
  sAlarm.AlarmTime.StoreOperation = RTC_STOREOPERATION_RESET;
  sAlarm.AlarmMask = RTC_ALARMMASK_DATEWEEKDAY;
  sAlarm.AlarmSubSecondMask = RTC_ALARMSUBSECONDMASK_ALL;
  sAlarm.AlarmDateWeekDaySel = RTC_ALARMDATEWEEKDAYSEL_DATE;
  sAlarm.AlarmDateWeekDay = 0x1;
  sAlarm.Alarm = RTC_ALARM_A;
  if (HAL_RTC_SetAlarm_IT(&hrtc, &sAlarm, RTC_FORMAT_BCD) != HAL_OK)
  {
    Error_Handler();
  }
}

code to go to sleep

	HAL_PWR_DisableWakeUpPin(PWR_WAKEUP_PIN1);
	__HAL_PWR_CLEAR_FLAG(PWR_FLAG_WU);
	HAL_PWR_EnableWakeUpPin(PWR_WAKEUP_PIN1);
	HAL_PWR_EnterSTANDBYMode();
	while (1)
	{
	    NVIC_SystemReset();
	}

Labels:
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6 REPLIES 6
MFahl.1
Associate

‎2021-03-05 12:37 AM

Hi, I have the same or similar problem. ALRAF is not set when returning from standby. I am on a different MCU, STM32F100.

For me all works according to the datasheets when I run in the debugger (ST-Link). However when I run outside the debugger the ALRAF bit never reads as 1. The MCU is returning (reset) perfectly from standby on RTC but I am not able to read a correct value on ALRAF.

Did you find a solution somewhere?

/Mats

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MFara.1346
Associate II

‎2022-09-12 04:28 AM

Any one found a solution for this?

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greffeb
Associate
In response to MFara.1346

‎2022-09-12 05:37 AM

I have found a workaround to differentiate source of wakeup

after the  SystemClock_Config(); i clear all wakeup flags.

  /* Check and handle if the system was resumed from StandBy mode */
  if(__HAL_PWR_GET_FLAG(PWR_FLAG_SB) != RESET)
  {
    /* Clear Standby flag */
     __HAL_PWR_CLEAR_FLAG(PWR_FLAG_SB);
  }
  /* Disable all used wakeup sources: PWR_WAKEUP_PIN1 */
  HAL_PWR_DisableWakeUpPin(PWR_WAKEUP_PIN1);
 
  /* Clear all related wakeup flags*/
  __HAL_PWR_CLEAR_FLAG(PWR_FLAG_WU);

then i compare current RTC date with expected Calendar alarm

  /**** check alarm wakeup ****/
  /* read programmed alarm */
  uint32_t tmpregalarm = (uint32_t) RTC->ALRMAR;
  int alr_hour = bcd2int((uint8_t)((tmpregalarm & (RTC_ALRMAR_HT  | RTC_ALRMAR_HU )) >> 16));
  int alr_min  = bcd2int((uint8_t)((tmpregalarm & (RTC_ALRMAR_MNT | RTC_ALRMAR_MNU)) >> 8 ));
  int alr_sec  = bcd2int((uint8_t) (tmpregalarm & (RTC_ALRMAR_ST  | RTC_ALRMAR_SU ))       );
  /* read current RTC */
  uint32_t tmpregrtc = (uint32_t) RTC->TR;
  int rtc_hour = bcd2int((uint8_t)((tmpregrtc & (RTC_TR_HT  | RTC_TR_HU )) >> 16));
  int rtc_min  = bcd2int((uint8_t)((tmpregrtc & (RTC_TR_MNT | RTC_TR_MNU)) >> 8 ));
  int rtc_sec  = bcd2int((uint8_t) (tmpregrtc & (RTC_TR_ST  | RTC_TR_SU ))       );
  /* if current date= alarm -> alarm wakeup */
  if(alr_hour==rtc_hour && alr_min==rtc_min && alr_sec==rtc_sec){lbSystemWakedUpByRtcAlarm = true ;}
  else                                                          {lbSystemWakedUpByRtcAlarm = false;}

if true, the source of wakeup was the alarm. If false, the source of wakeup was from another source( WKUP PIN or RST in my case)

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MFara.1346
Associate II
In response to greffeb

‎2022-09-12 06:00 AM

Many thanks. Really appreciated. I also asked this question from ST if I get any different reply I will share it here for everyone to use.

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Cgelectronics
Associate II

‎2023-10-20 12:39 PM

I don't know if it is the same case for the STM32L071 as the STM32F103, but after many attempts and tests, I have opened a ticket with ST, and I've got this answer:

"It turns out that the ALRF flag (and indeed the whole register) is not kept through system reset - which occurs at wake up. Although this is not explicitly documented. The only similar flag that is kept is WUF in PWR_CSR register but this is combines wakeup from button and RTC alarm so not helpful in your case.
The solution is then the one you already applied - compare the current time to a predefined one from Flash/backup registers."

Check the following post if you have not solved this topic yet:

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