STM32WL how to enable RTC subsecond underflow interrupt

[SimonLaw]

STM32WL lorawan middleware use a RTC subsecond underflow interrupt update tick instead systick，but the subsecond underflow interrupt never entered.It seems interrupt not enabled, so I manually enable RTC subsecond underflow interrupt but the handler still never accessed.

/* RTC init function */
void MX_RTC_Init(void)
{

  /* USER CODE BEGIN RTC_Init 0 */

  /* USER CODE END RTC_Init 0 */

  RTC_TimeTypeDef sTime = {0};
  RTC_DateTypeDef sDate = {0};
  RTC_AlarmTypeDef sAlarm = {0};

  /* USER CODE BEGIN RTC_Init 1 */

  /* USER CODE END RTC_Init 1 */

  /** Initialize RTC Only
  */
  hrtc.Instance = RTC;
  hrtc.Init.HourFormat = RTC_HOURFORMAT_24;
  hrtc.Init.AsynchPrediv = RTC_PREDIV_A;
  hrtc.Init.SynchPrediv = RTC_PREDIV_S;
  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;
  hrtc.Init.OutPutPullUp = RTC_OUTPUT_PULLUP_NONE;
  hrtc.Init.BinMode = RTC_BINARY_NONE;
  if (HAL_RTC_Init(&hrtc) != HAL_OK)
  {
    Error_Handler();
  }

  /* USER CODE BEGIN Check_RTC_BKUP */

  /* USER CODE END Check_RTC_BKUP */

  /** Initialize RTC and set the Time and Date
  */
  sTime.Hours = 0x0;
  sTime.Minutes = 0x0;
  sTime.Seconds = 0x0;
  sTime.DayLightSaving = RTC_DAYLIGHTSAVING_NONE;
  sTime.StoreOperation = RTC_STOREOPERATION_RESET;
  if (HAL_RTC_SetTime(&hrtc, &sTime, RTC_FORMAT_BCD) != HAL_OK)
  {
    Error_Handler();
  }
  sDate.WeekDay = RTC_WEEKDAY_MONDAY;
  sDate.Month = RTC_MONTH_JANUARY;
  sDate.Date = 0x1;
  sDate.Year = 0x0;

  if (HAL_RTC_SetDate(&hrtc, &sDate, RTC_FORMAT_BCD) != HAL_OK)
  {
    Error_Handler();
  }

  /** Enable the Alarm A
  */
  sAlarm.AlarmTime.Hours = 0x0;
  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_NONE;
  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();
  }

  /** Enable the WakeUp
  */
  if (HAL_RTCEx_SetWakeUpTimer_IT(&hrtc, 0, RTC_WAKEUPCLOCK_RTCCLK_DIV16, 0) != HAL_OK)
  {
    Error_Handler();
  }
  /* USER CODE BEGIN RTC_Init 2 */

  /* USER CODE END RTC_Init 2 */

}

void HAL_RTC_MspInit(RTC_HandleTypeDef* rtcHandle)
{

  RCC_PeriphCLKInitTypeDef PeriphClkInitStruct = {0};
  if(rtcHandle->Instance==RTC)
  {
  /* USER CODE BEGIN RTC_MspInit 0 */

  /* USER CODE END RTC_MspInit 0 */

  /** Initializes the peripherals clocks
  */
    PeriphClkInitStruct.PeriphClockSelection = RCC_PERIPHCLK_RTC;
    PeriphClkInitStruct.RTCClockSelection = RCC_RTCCLKSOURCE_LSE;

    if (HAL_RCCEx_PeriphCLKConfig(&PeriphClkInitStruct) != HAL_OK)
    {
      Error_Handler();
    }

    /* RTC clock enable */
    __HAL_RCC_RTC_ENABLE();
    __HAL_RCC_RTCAPB_CLK_ENABLE();

    /* RTC interrupt Init */
    HAL_NVIC_SetPriority(RTC_WKUP_IRQn, 0, 0);
    HAL_NVIC_EnableIRQ(RTC_WKUP_IRQn);
    HAL_NVIC_SetPriority(RTC_Alarm_IRQn, 0, 0);
    HAL_NVIC_EnableIRQ(RTC_Alarm_IRQn);
  /* USER CODE BEGIN RTC_MspInit 1 */

  /* USER CODE END RTC_MspInit 1 */
  }
}

PS: As far, I can’t find any configuration about subsecond underflow interrupt in CubeMX and any code snippet in offical example project.

[Victor_D]

Hello Simon,

Some points that are not included in the code you provided :

• Enabling the SSRU IRQ: TAMP_STAMP_LSECSS_SSRU_IRQHandler
• Calling the HAL_RTCEx_SSRUIRQHandler() function in the TAMP_STAMP_LSECSS_SSRU_IRQn interrupt
• Enabling the SSRU IT with the HAL_RTCEx_SetSSRU_IT() function inside the MX_RTC_Init() function
• Rewriting the weak function HAL_RTCEx_SSRUEventCallback() with your code

Additionally, by default, Cube MX sets the wake-up counter to 0. You should modify it to a value such as 0x0800, which will give you an interrupt every second with the wake-up clock selected with RTC/16.

Best Regards,

Victor