STM32L152 y RTC

Todo lo que tengo es este problema. Quiero configurar mi STM32L152 para que entre en modo de parada y 4 segundos más tarde, me despierto para siempre. Yo uso STM32CubeMX para la configuración.

Esta es mi configuración:

• Habilitar la interrupción global de RCC
• Habilita la línea EXTI [15:10] interrupción
• Use LSE 32.768 kHz para RTC
• Vea un ejemplo fácil, pero no funciona. Este es mi código:

int main(void)
{
    /* USER CODE BEGIN 1 */
    HAL_PWR_EnableBkUpAccess(); // Enable PWR backup domain access (RTC, BKReg)
    /* USER CODE END 1 */
    /* MCU Configuration----------------------------------------------------------*/
    /* Reset of all peripherals, Initializes the Flash interface and the Systick. */
    HAL_Init();
    /* Configure the system clock */
    SystemClock_Config();
    /* Initialize all configured peripherals */
    MX_GPIO_Init();
    MX_RTC_Init();
    MX_USART1_UART_Init();
    MX_USART2_UART_Init();
    MX_ADC_Init();
    MX_I2C1_Init();
    MX_TIM3_Init();
    MX_TIM11_Init();
    MX_USART3_UART_Init();

    /* USER CODE BEGIN 2 */

    /* USER CODE END 2 */

    /* Infinite loop */
    /* USER CODE BEGIN WHILE */
    while (1)
    {
        /* USER CODE END WHILE */

        /* USER CODE BEGIN 3 */

        HAL_Delay(1500);
        HAL_UART_Transmit(&huart2, dataS7, 2, 1000);


        /* ## Setting the Wake up time - from example ##########################*/
        /*  RTC Wakeup Interrupt Generation:
        Wakeup Time Base = (RTC_WAKEUPCLOCK_RTCCLK_DIV /(LSE or LSI))
        Wakeup Time = Wakeup Time Base * WakeUpCounter
        = (RTC_WAKEUPCLOCK_RTCCLK_DIV /(LSE or LSI)) * WakeUpCounter
        ==> WakeUpCounter = Wakeup Time / Wakeup Time Base

        To configure the wake up timer to 4s the WakeUpCounter is set to 0x1FFF:
        RTC_WAKEUPCLOCK_RTCCLK_DIV = RTCCLK_Div16 = 16
        Wakeup Time Base = 16 /(~39.000 KHz) = ~0,410 ms
        Wakeup Time = ~4 s = 0,410 ms  * WakeUpCounter
        ==> WakeUpCounter = ~4 s/0,410 ms = 9750 = 0x2616 */
        HAL_RTCEx_SetWakeUpTimer_IT(&hrtc, 0x2616, RTC_WAKEUPCLOCK_RTCCLK_DIV16);

        /* Enter Stop Mode */
        HAL_PWR_EnterSTOPMode(PWR_LOWPOWERREGULATOR_ON, PWR_STOPENTRY_WFI);
    }

    /* USER CODE END 3 */

}


/** System Clock Configuration*/
void SystemClock_Config(void)
{
    RCC_OscInitTypeDef RCC_OscInitStruct;
    RCC_ClkInitTypeDef RCC_ClkInitStruct;
    RCC_PeriphCLKInitTypeDef PeriphClkInit;

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

    /**Initializes the CPU, AHB and APB busses clocks
    */
    RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSI|RCC_OSCILLATORTYPE_LSE;
    RCC_OscInitStruct.LSEState = RCC_LSE_ON;
    RCC_OscInitStruct.HSIState = RCC_HSI_ON;
    RCC_OscInitStruct.HSICalibrationValue = 16;
    RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
    RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSI;
    RCC_OscInitStruct.PLL.PLLMUL = RCC_PLL_MUL6;
    RCC_OscInitStruct.PLL.PLLDIV = RCC_PLL_DIV3;
    if (HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK)
    {
        Error_Handler();
    }
    /**Initializes the CPU, AHB and APB busses 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_RTC;
    PeriphClkInit.RTCClockSelection = RCC_RTCCLKSOURCE_LSE;
    if (HAL_RCCEx_PeriphCLKConfig(&PeriphClkInit) != HAL_OK)
    {
        Error_Handler();
    }

    /**Configure the Systick interrupt time
    */
    HAL_SYSTICK_Config(HAL_RCC_GetHCLKFreq()/1000);

    /**Configure the Systick
    */
    HAL_SYSTICK_CLKSourceConfig(SYSTICK_CLKSOURCE_HCLK);

    /* SysTick_IRQn interrupt configuration */
    HAL_NVIC_SetPriority(SysTick_IRQn, 0, 0);
}


/* RTC init function */
static void MX_RTC_Init(void)
{
    /**Initialize RTC Only
    */
    hrtc.Instance = RTC;
    hrtc.Init.HourFormat = RTC_HOURFORMAT_24;
    hrtc.Init.AsynchPrediv = 127;
    hrtc.Init.SynchPrediv = 255;
    hrtc.Init.OutPut = RTC_OUTPUT_DISABLE;
    hrtc.Init.OutPutPolarity = RTC_OUTPUT_POLARITY_HIGH;
    hrtc.Init.OutPutType = RTC_OUTPUT_TYPE_OPENDRAIN;
    if (HAL_RTC_Init(&hrtc) != HAL_OK)
    {
        Error_Handler();
    }
}


/**
* @brief  RTC Wake Up callback
*/
void HAL_RTCEx_WakeUpTimerEventCallback(RTC_HandleTypeDef *hrtc)
{
    SystemClock_Config();
    /* Clear Wake Up Flag */
    __HAL_PWR_CLEAR_FLAG(PWR_FLAG_WU);
    HAL_Delay(200);
    HAL_GPIO_TogglePin(GPIOA, GPIO_PIN_5);          // TOGGLE THE LED
    HAL_UART_Transmit(&huart2, data3, 2, 1000);

    HAL_Delay(1200);
}

No veo el interruptor LED. ¿Cuál es la razón?