STM32L053 LSE CSS not trigger

[ShimiaoWang]

I tested the LSE CSS function on the Nucleo-L053, but I found that short-circuiting the crystal oscillator pins failed to trigger the CSS interrupt. The code configuration is as follows

plz give a clue or the flow of LSECSS

void SystemClock_Config(void)
{
  RCC_OscInitTypeDef RCC_OscInitStruct = {0};
  RCC_ClkInitTypeDef RCC_ClkInitStruct = {0};
  RCC_PeriphCLKInitTypeDef PeriphClkInit = {0};

  /** Configure the main internal regulator output voltage
  */
  __HAL_PWR_VOLTAGESCALING_CONFIG(PWR_REGULATOR_VOLTAGE_SCALE1);

  /** Configure LSE Drive Capability
  */
  HAL_PWR_EnableBkUpAccess();
  __HAL_RCC_LSEDRIVE_CONFIG(RCC_LSEDRIVE_LOW);

  /** Initializes the RCC Oscillators according to the specified parameters
  * in the RCC_OscInitTypeDef structure.
  */
  RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSI|RCC_OSCILLATORTYPE_LSE;
  RCC_OscInitStruct.LSEState = RCC_LSE_ON;
  RCC_OscInitStruct.HSIState = RCC_HSI_ON;
  RCC_OscInitStruct.HSICalibrationValue = RCC_HSICALIBRATION_DEFAULT;
  RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
  RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSI;
  RCC_OscInitStruct.PLL.PLLMUL = RCC_PLLMUL_4;
  RCC_OscInitStruct.PLL.PLLDIV = RCC_PLLDIV_2;
  if (HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK)
  {
    Error_Handler();
  }

  /** Initializes the CPU, AHB and APB buses clocks
  */
  RCC_ClkInitStruct.ClockType = RCC_CLOCKTYPE_HCLK|RCC_CLOCKTYPE_SYSCLK
                              |RCC_CLOCKTYPE_PCLK1|RCC_CLOCKTYPE_PCLK2;
  RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_PLLCLK;
  RCC_ClkInitStruct.AHBCLKDivider = RCC_SYSCLK_DIV1;
  RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV1;
  RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV1;

  if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_1) != HAL_OK)
  {
    Error_Handler();
  }
  PeriphClkInit.PeriphClockSelection = RCC_PERIPHCLK_USART2|RCC_PERIPHCLK_RTC;
  PeriphClkInit.Usart2ClockSelection = RCC_USART2CLKSOURCE_PCLK1;
  PeriphClkInit.RTCClockSelection = RCC_RTCCLKSOURCE_LSE;
  if (HAL_RCCEx_PeriphCLKConfig(&PeriphClkInit) != HAL_OK)
  {
    Error_Handler();
  }
  /** Enables the Clock Security System
  */

  HAL_RCCEx_EnableLSECSS_IT();
	
  HAL_RCC_MCOConfig(RCC_MCO1, RCC_MCO1SOURCE_LSE, RCC_MCODIV_1);
}

void RTC_IRQHandler(void)
{
  /* USER CODE BEGIN RTC_IRQn 0 */
  HAL_RCCEx_LSECSS_IRQHandler();
  /* USER CODE END RTC_IRQn 0 */
  HAL_RTC_AlarmIRQHandler(&hrtc);
  /* USER CODE BEGIN RTC_IRQn 1 */

  /* USER CODE END RTC_IRQn 1 */
}

void HAL_RCCEx_LSECSS_Callback(void)
{
	printf("LSE CSS\r\n");
}

No print output was observed when the crystal oscillator was short-circuited, and debugging showed that the interrupt service routine was not entered.

[TDK]

RTC_IRQHandler is not the handler for the CSS.

Is the interrupt enabled?

Should be a HAL_NVIC_EnableIRQ call somewhere. It's not in the code you presented.

Is HAL_RCCEx_LSECSS_IRQHandler defined? It's not in the code you presented.

[ShimiaoWang]

Thank you for your reply

RTC interrupt has been enabled.

HAL_RCCEx_LSECSS_IRQHandler  in the HAL library.

[TDK]

I don't see how the RTC or its interrupt is relevant here. Maybe I'm missing something.

[ShimiaoWang]

I checked the manual. CSS_LSE IT is mapped on RTC EXTI line 19.So I enabled the RTC interrupt. 

I also tried to open this interrupt, but cannot be triggered.