Posted on May 11, 2015 at 15:27Hi,
I have a big problem with waking up the STM32F4 MCU from STANDBY mode by RTC alarm and I dont see any solutions...
The problem is that the MCU wakes up only sometimes from the RTC Alarm. Usually like 3 times in a row and then stops. Waking up by user button is fine...
I use LSE and clock itself works fine even when RTC alarm doesnt wake up the MCU...It looks like there is some problem with redefinition of the RTC alarm, possibly some IRQ flags...
I found some topics regarding same problems but reading them all I think that I am doing everything right...
The operation itself should be simple...I manually set up RTC alarm and get to STANDBY mode and after that the MCU wakes up does something and then goes back to STANDBY in a loop until I interupt it manually by button...
Manual set up looks like this:
// Load time and date values from RTC
RTC_AWU_GetDateTime(&time, RTC_AWU_Format_BIN);
// Set up RTC alarm
alarm_time.hours = time.hours;
alarm_time.minutes = time.minutes;
alarm_time.seconds = time.seconds + 5;
alarm_time.alarmtype = RTC_AWU_AlarmType_DayInWeek;
alarm_time.day = 1;
RTC_AWU_SetAlarm(RTC_AWU_Alarm_B, &alarm_time, RTC_AWU_Format_BIN);
/* Power down */
// Disable wakeup pin (BUTTON = PA0)
PWR_WakeUpPinCmd(DISABLE);
// Clear standby/wakeup flag
PWR_ClearFlag(PWR_FLAG_SB | PWR_FLAG_WU);
// Enable wakeup pin (BUTTON = PA0)
PWR_WakeUpPinCmd(ENABLE);
// Go to standby mode
PWR_EnterSTANDBYMode();
Then the loop exacly the same:
// RTC init (PWR_BackupAccessCmd(ENABLE) present here)
RTC_AWU_Init(RTC_AWU_ClockSource_External);
if (RTC_GetITStatus(RTC_IT_ALRB) != RESET){
/*Some code here*/
// Load time and date values from RTC
RTC_AWU_GetDateTime(&time, RTC_AWU_Format_BIN);
// Set up RTC alarm
alarm_time.hours = time.hours;
alarm_time.minutes = time.minutes;
alarm_time.seconds = time.seconds + 5;
alarm_time.alarmtype = RTC_AWU_AlarmType_DayInWeek;
alarm_time.day = 1;
RTC_AWU_SetAlarm(RTC_AWU_Alarm_B, &alarm_time, RTC_AWU_Format_BIN);
/* Power down */
// Disable wakeup pin (BUTTON = PA0)
PWR_WakeUpPinCmd(DISABLE);
// Clear standby/wakeup flag
PWR_ClearFlag(PWR_FLAG_SB | PWR_FLAG_WU);
// Enable wakeup pin (BUTTON = PA0)
PWR_WakeUpPinCmd(ENABLE);
// Go to standby mode
PWR_EnterSTANDBYMode();
}
The RTC_AWU_SetAlarm function looks like this...
// Disable Alarm B
RTC_AlarmCmd(RTC_Alarm_B, DISABLE);
// Disable Alarm B interrupt
RTC_ITConfig(RTC_IT_ALRB, DISABLE);
// Clear Alarm B pending bit
RTC_ClearFlag(RTC_IT_ALRB);
// Clear RTC Alarm pending bit
EXTI_ClearITPendingBit(EXTI_Line17);
// Configure EXTI 17 as interrupt
EXTI_InitStruct.EXTI_Line = EXTI_Line17;
EXTI_InitStruct.EXTI_Mode = EXTI_Mode_Interrupt;
EXTI_InitStruct.EXTI_Trigger = EXTI_Trigger_Rising;
EXTI_InitStruct.EXTI_LineCmd = ENABLE;
EXTI_Init(&EXTI_InitStruct);
// Configure the RTC Alarm Interrupt
NVIC_InitStruct.NVIC_IRQChannel = RTC_Alarm_IRQn;
NVIC_InitStruct.NVIC_IRQChannelPreemptionPriority = 0;
NVIC_InitStruct.NVIC_IRQChannelSubPriority = 0;
NVIC_InitStruct.NVIC_IRQChannelCmd = ENABLE;
NVIC_Init(&NVIC_InitStruct);
// Set RTC alarm settings
// Set alarm time
RTC_AlarmStruct.RTC_AlarmTime.RTC_Hours = DataTime->hours;
RTC_AlarmStruct.RTC_AlarmTime.RTC_Minutes = DataTime->minutes;
RTC_AlarmStruct.RTC_AlarmTime.RTC_Seconds = DataTime->seconds;
RTC_AlarmStruct.RTC_AlarmMask = RTC_AlarmMask_DateWeekDay;
etc...
// Configure the RTC Alarm B
RTC_SetAlarm(format, RTC_Alarm_B, &RTC_AlarmStruct);
// Clear Alarm B pending bit
RTC_ClearFlag(RTC_IT_ALRB);
// Enable Alarm B interrupt
RTC_ITConfig(RTC_IT_ALRB, ENABLE);
// Enable Alarm B
RTC_AlarmCmd(RTC_Alarm_B, ENABLE);
Thanks very much for your help...
#rtc #stm32f4 #alarm
