SHUTDOWN mode WUP Pin works but no WUF is set at wakeup

[oga]

I've a custom board that going to SHUTDOWN OFF mode 

I'm using the LPM lib and it use PA0 as WAKEUP PIN 

it wakes up on a High level signal 

void PWR_EnterOffMode(void)
{
/* USER CODE BEGIN PWR_EnterOffMode_1 */

	// refer to the following link for more details on how to go to Off Mode
	// https://community.st.com/t5/stm32-mcus-embedded-software/how-to-enter-standby-or-shutdown-mode-on-stm32/m-p/145849
	// https://community.st.com/t5/stm32-mcus-wireless/stm32wb55-shutdown-mode-standby-mode-wake-up-with-syswkup-pin/m-p/67480#M812

	/* Enable Backup domain write */
	HAL_PWR_EnableBkUpAccess();

	/*Disable RTC */
	CLEAR_BIT(RCC->BDCR, RCC_BDCR_RTCEN);

	/* Disable LSE */
	CLEAR_BIT(RCC->BDCR, RCC_BDCR_LSEON);


	/* Disabel Backup domain write */
	HAL_PWR_DisableBkUpAccess();
	/* See : https://community.st.com/t5/stm32-mcus-embedded-software/how-to-enter-standby-or-shutdown-mode-on-stm32/m-p/145849 */

/* USER CODE END PWR_EnterOffMode_1 */
  /**
   * The systick should be disabled for the same reason than when the device enters stop mode because
   * at this time, the device may enter either OffMode or StopMode.
   */
  HAL_SuspendTick();

  EnterLowPower();

  /************************************************************************************
   * ENTER OFF MODE
   ***********************************************************************************/
  /*
   * There is no risk to clear all the WUF here because in the current implementation, this API is called
   * in critical section. If an interrupt occurs while in that critical section before that point,
   * the flag is set and will be cleared here but the system will not enter Off Mode
   * because an interrupt is pending in the NVIC. The ISR will be executed when moving out
   * of this critical section
   */
  LL_PWR_ClearFlag_WU();

  LL_PWR_SetPowerMode(LL_PWR_MODE_SHUTDOWN);

  LL_LPM_EnableDeepSleep(); /**< Set SLEEPDEEP bit of Cortex System Control Register */

  /* Disable all used wakeup sources */
  HAL_PWR_DisableWakeUpPin(PWR_WAKEUP_PIN1_LOW);

  /* Clear all wake up Flag */
  __HAL_PWR_CLEAR_FLAG(PWR_FLAG_WUF1);

  /* Enable WakeUp Pin PWR_WAKEUP_PIN1 connected to PA0 */
  HAL_PWR_EnableWakeUpPin(PWR_WAKEUP_PIN1_HIGH);

  /* Clear all related wakeup flags*/
  __HAL_PWR_CLEAR_FLAG(PWR_FLAG_WUF1);

  // Disable debug, trace and IWDG in low-power modes
  DBGMCU->CR = 0; 
  /**
   * This option is used to ensure that store operations are completed
   */
#if defined (__CC_ARM) || defined (__ARMCC_VERSION)
  __force_stores(); // comment : looks that CC_ARM or ARMCC_VERSION are not define and therefore not build 
#endif
  for(;;){
	__DSB();
	__WFI();
  }
}

it works ok for waking the cpu but I have no WF1 set in PWR->SR1 register at wakeup 

so I'm not able to differenciate a WKUP of a BORRST

I've try different relative orders of actions and nothing seems to act on WUFx

any idea would be greatly appreciated 

[STTwo-32]

Hello @oga 

The WUF1 flag in the `PWR->SR1` register is not set after waking up from Shutdown mode because, as stated in the RM0473, A power-on reset occurs when exiting from Shutdown mode. All registers (except for the ones in the Backup domain) are reset after wake-up from Shutdown. So, the WUF1 is reset after exiting the Shutdown mode.

Best Regards.

STTwo-32