RTC Alarm EventCallback called only 1 time

[Richard Lowe]

Working with the RTC I'm having some issue with the callback only being called a single time.

void HAL_RTC_AlarmAEventCallback(RTC_HandleTypeDef *hrtc) {
  RTC_AlarmTypeDef sAlarm;
  uint32_t hobb_time;

  __HAL_RTC_ALARM_CLEAR_FLAG(hrtc, RTC_FLAG_ALRAF); // Does not seem to change the ISR register

  hobb_time = HAL_RTCEx_BKUPRead(hrtc, RTC_BKP_DR1);

  // Write the new hobbs incremented value to backup register
  HAL_PWR_EnableBkUpAccess();
  HAL_RTCEx_BKUPWrite(hrtc, RTC_BKP_DR1, ++hobb_time);
  HAL_PWR_DisableBkUpAccess();

  HAL_RTC_GetAlarm(hrtc, &sAlarm, RTC_ALARM_A, FORMAT_BIN);

  if(sAlarm.AlarmTime.Minutes > 58)
  {
    sAlarm.AlarmTime.Minutes = 0;
  }
  else
  {
    sAlarm.AlarmTime.Minutes = sAlarm.AlarmTime.Minutes + 1;
  }

  while(HAL_RTC_SetAlarm_IT(hrtc, &sAlarm, RTC_FORMAT_BIN) != HAL_OK){}
}

I have the alarm being triggered every 1 minute. I can see the alarmA flag and try to clear it with this macro: 

__HAL_RTC_ALARM_CLEAR_FLAG(hrtc, RTC_FLAG_ALRAF);

But the ISR register is unaffected. 

I've masked the DAYS, SECONDS, etc.

sAlarm.AlarmMask = RTC_ALARMMASK_DATEWEEKDAY|RTC_ALARMMASK_HOURS
                              |RTC_ALARMMASK_SECONDS;
sAlarm.AlarmSubSecondMask = RTC_ALARMSUBSECONDMASK_ALL;

Anybody working with alarm events that only trigger a single time?

[Richard Lowe]

I still have nothing. Seems like the HAL functions to perform all the actions called for in the datasheet. 

• Clear the interrupt on the Alarm
• Clear EXTI interrupt
• Write to protection registers
• Re-enable the interrupt

ISR Flag does not clear:

Still can only get a single interrupt. Single alarm handler, that's it..... Please advise.

[Richard Lowe]

This is in HAL_RTC_SetAlarm_IT. Seems to include everything in the Reference Manual.

/* Disable the write protection for RTC registers */
__HAL_RTC_WRITEPROTECTION_DISABLE(hrtc);

/* Configure the Alarm register */
if(sAlarm->Alarm == RTC_ALARM_A)
{
   /* Disable the Alarm A interrupt */
   __HAL_RTC_ALARMA_DISABLE(hrtc);

   /* Clear flag alarm A */
   __HAL_RTC_ALARM_CLEAR_FLAG(hrtc, RTC_FLAG_ALRAF);

   tickstart = HAL_GetTick();
   /* Wait till RTC ALRAWF flag is set and if timeout is reached exit */
#if defined(TAMP)
    while (READ_BIT(hrtc->Instance->ICSR, RTC_FLAG_ALRAWF) == 0U)
#else
    while (__HAL_RTC_ALARM_GET_FLAG(hrtc, RTC_FLAG_ALRAWF) == 0U)
#endif /* TAMP */
    {
      if((HAL_GetTick() - tickstart) > RTC_TIMEOUT_VALUE)
      {
        /* Enable the write protection for RTC registers */
        __HAL_RTC_WRITEPROTECTION_ENABLE(hrtc);

        hrtc->State = HAL_RTC_STATE_TIMEOUT;

        /* Process Unlocked */
        __HAL_UNLOCK(hrtc);

        return HAL_TIMEOUT;
      }
    }

    hrtc->Instance->ALRMAR = (uint32_t)tmpreg;
    /* Configure the Alarm A Sub Second register */
    hrtc->Instance->ALRMASSR = subsecondtmpreg;
    /* Configure the Alarm state: Enable Alarm */
    __HAL_RTC_ALARMA_ENABLE(hrtc);
    /* Configure the Alarm interrupt */
    __HAL_RTC_ALARM_ENABLE_IT(hrtc, RTC_IT_ALRA);

[Richard Lowe · Accepted solution]

The following lines will disable the RTC and cause all my issues:

HAL_PWR_EnableBkUpAccess();
HAL_RTCEx_BKUPWrite(hrtc, RTC_BKP_DR1, ++hobb_time);
HAL_PWR_DisableBkUpAccess();

The first line is already called in the RTC_Init() function, but the the last line, HAL_PWR_DisableBkUpAccess() will disable the RTC..... So that is why it was only called once.