After wake up from stop mode with a RTC Alarm the device stop working when I use the uart link. Do you know why ?

[YMAIL]

Hi !

I got a discovery board B-L072cz-LRWAN1. It go to stop mode and when the Alarm trig it wake up and run the program correctly. But when I use the uart for print or anything else, the program stop.

Here is my code. It's based on the cube-LRWAN1 example :

int main()
{
    HAL_Init( );
 
    SystemClock_Config( );
 
    DBG_Init( );
 
    HW_Init( );
 
	while(1)
       {
          PRINTF("Sleep\r");
	  SX1276SetSleep();
	  HAL_Delay(200);
	  stm32l_lowPowerSetup();
	  stm32l_lowPowerResume();
	  PRINTF("Wake\r");
       }
}
 
void stm32l_lowPowerSetup(void)
{
__HAL_RCC_PWR_CLK_ENABLE(); // Enable Power Control clock
HAL_PWREx_EnableUltraLowPower(); // Ultra low power mode
HAL_PWREx_EnableFastWakeUp(); // Fast wake-up for ultra low power mode
 
// Disable Unused Gpios
_stm32l_disableGpios(); // Disable GPIOs based on configuration
 
HW_RTC_SetAlarm(10000);
// Switch to STOPMode
HAL_PWR_EnterSTOPMode(PWR_LOWPOWERREGULATOR_ON, PWR_STOPENTRY_WFI);
}
 
void stm32l_lowPowerResume(void)
{
 
    HAL_Init( );
 
    SystemClock_Config( );
 
    HAL_RTC_MspInit(&hrtc);
 
    DBG_Init( );
 
    HW_Init( );
    HAL_UART_MspInit(&huart2);
}
 
void HAL_UART_MspInit(UART_HandleTypeDef *huart)
{
  static DMA_HandleTypeDef hdma_tx;
  
  
  /*##-1- Enable peripherals and GPIO Clocks #################################*/
  /* Enable GPIO TX/RX clock */
  USARTx_TX_GPIO_CLK_ENABLE();
  USARTx_RX_GPIO_CLK_ENABLE();
 
  /* Enable USARTx clock */
  USARTx_CLK_ENABLE();
 
  /* Enable DMA clock */
  DMAx_CLK_ENABLE();
  
  /*##-2- Configure peripheral GPIO ##########################################*/  
  /* UART  pin configuration  */
  vcom_IoInit();
 
  /*##-3- Configure the DMA ##################################################*/
  /* Configure the DMA handler for Transmission process */
  hdma_tx.Instance                 = USARTx_TX_DMA_CHANNEL;
  hdma_tx.Init.Direction           = DMA_MEMORY_TO_PERIPH;
  hdma_tx.Init.PeriphInc           = DMA_PINC_DISABLE;
  hdma_tx.Init.MemInc              = DMA_MINC_ENABLE;
  hdma_tx.Init.PeriphDataAlignment = DMA_PDATAALIGN_BYTE;
  hdma_tx.Init.MemDataAlignment    = DMA_MDATAALIGN_BYTE;
  hdma_tx.Init.Mode                = DMA_NORMAL;
  hdma_tx.Init.Priority            = DMA_PRIORITY_LOW;
#ifndef STM32L152xE
  hdma_tx.Init.Request             = USARTx_TX_DMA_REQUEST;
#endif
  HAL_DMA_Init(&hdma_tx);
 
  /* Associate the initialized DMA handle to the UART handle */
  __HAL_LINKDMA(huart, hdmatx, hdma_tx);
    
  /*##-4- Configure the NVIC for DMA #########################################*/
  /* NVIC configuration for DMA transfer complete interrupt (USART1_TX) */
  HAL_NVIC_SetPriority(USARTx_DMA_TX_IRQn, USARTx_Priority, 1);
  HAL_NVIC_EnableIRQ(USARTx_DMA_TX_IRQn);
    
  /* NVIC for USART, to catch the TX complete */
  HAL_NVIC_SetPriority(USARTx_IRQn, USARTx_DMA_Priority, 1);
  HAL_NVIC_EnableIRQ(USARTx_IRQn);
}