RTC ALARM A Stops working after Mid-Night

[Soham Jani]

I'm using STM32L152RE with FreeRtos for our project. We use RTC HAL library to handle the Calendar alarms.

I'm in a strange situation where the RTC_ALARM_A does not generate an interrupt after 12 midnight.

The current system is setup to generate an alarm interrupt every 1hr. This functionality is implemented in the following manner -

```

RTC Alarm Generated -> Interrupt Handler Triggers an Event -> Event gathers current time & adds 1hr to it, activates the alarm again.

```

void HourlyAlarmRoutine ( void )   
{
	        // Get current caleneder Time
		ALARM_sTime_t sTime;
		ALARM_sDate_t sDate;
		ALARM_GetCalendarTime(&sTime, &sDate);
 
		// Set Alarm after (x + 1) hours
		ALARM_sAlarm_t sAlarm;
		sAlarm.Alarm 				= ALARM_BACKUP_ID;
		sAlarm.AlarmDateWeekDay      = 0;
		sAlarm.AlarmDateWeekDaySel = RTC_ALARMDATEWEEKDAYSEL_DATE;
		sAlarm.AlarmMask 			= RTC_ALARMMASK_DATEWEEKDAY;
		sAlarm.AlarmTime.TimeFormat = RTC_HOURFORMAT12_AM;
		sAlarm.AlarmTime.Seconds 	 = 00;
		sAlarm.AlarmTime.Minutes 	= sTime.Minutes;
		sAlarm.AlarmTime.Hours 		= ( sTime.Hours + uBackupCheckingHours ) % 24;
		ALARM_ActivateAlarm(&sAlarm);
}
 
void ALARM_ActivateAlarm(ALARM_sAlarm_t* p_sAlarm)
{
	// Not using SubSecond module
	p_sAlarm->AlarmTime.SubSeconds 	= 0;
	p_sAlarm->AlarmSubSecondMask 	= RTC_ALARMSUBSECONDMASK_NONE;
 
	if (HAL_RTC_SetAlarm_IT(m_rtcHandles[ALARM_RTC_ID], (RTC_AlarmTypeDef*)p_sAlarm,RTC_FORMAT_BIN)!= HAL_OK)
	{
              // Handle Error 
	}
 
    HAL_NVIC_SetPriority(RTC_Alarm_IRQn, 1, 0);
    HAL_NVIC_EnableIRQ(RTC_Alarm_IRQn);
}

The code works perfectly until after midnight. i.e It generates an interrupt every hour until after 12 midnight ( 00 hours ) . Trying to set an alarm for 1am throws and error.

Can anyone help me spot the mistake ?

Thanks

[Soham Jani]

yes I'm sure that it is not in BCD Format. The always pass `RTC_FORMAT_BIN` when setting a alarm.

The value of `uBackupCheckingHours` can be any whole number from 1-23.

[After Forever]

> The always pass `RTC_FORMAT_BIN` when setting a alarm.

I can see that, but the call to HAL_RTC_GetTime (where you should pass RTC_FORMAT_BIN too) was not pasted, I guess it's in your ALARM_GetCalendarTime function.

> can be any whole number from 1-23.

The comment is saying "Set Alarm after (x + 1) hours", so I guess in the current case it's always 1?

[Soham Jani]

> I can see that, but the call to HAL_RTC_GetTime (where you should pass RTC_FORMAT_BIN too) was not pasted, I guess it's in your ALARM_GetCalendarTime function.

Yes, it does exactly that. Calls HAL_RTC_GetTime() with RTC_FORMAT_BIN

> The comment is saying "Set Alarm after (x + 1) hours", so I guess in the current case it's always 1?

That is correct, in the following case/example it is 1 hour. But it has been coded to take in changing hour values.

[tarasov.alex.m]

Hm... I was sure, that was the case. Ok, the way you set hours is fine. It should be something else.

What I see now is that you set "sAlarm.DateWeekDay" to an invalid value (it must be between 1 and 31). Probably it somehow affects the alarm, I can't check it right now, maybe will do it later. Try to set the field to a valid number.

[Soham Jani]

That is exactly what I did next. I realized it was an invalid value. So I set "sAlarm.DateWeekDay" to 1. Since I already have the mask set to ignore weekday_date, it should not matter anyway. But I can confirm that it does not change the situation.

Appreciate the quick response 🙂

[urath]

My answer was deleted? even trying to help someone nowadays looks a crime..

[Soham Jani]

I can still see your answer.

[tarasov.alex.m]

@Soham Jani​ Can you write here your current version of HourlyAlarmRoutine? And also what version of stm32f4xx_hal_rtc.c (it can be found at the begining of the file) are you using?