FDCAN Tx callback not triggered on STM32U5

[dlagyals]

I’ve written code that performs a CAN Tx transmission when an interrupt occurs while in STOP2 mode.
The transmission request via HAL_FDCAN_AddMessageToTxFifoQ() succeeds,
but the HAL_FDCAN_TxEventFifoCallback(FDCAN_HandleTypeDef *hfdcan, uint32_t TxEventFifoITs) callback is never triggered.
The GPIO interrupt callback (HAL_GPIO_EXTI_Rising_Callback) works as expected,
and I can see "HAL_CAN_AddTxMessage start" being printed, which means the transmission request was made.
However, it seems like the transmission is not actually completed.
Why is the Tx event not being triggered?

/* USER CODE BEGIN Header */
/**
  ******************************************************************************
  * @file           : main.c
  * @brief          : Main program body
  ******************************************************************************
  * @attention
  *
  * Copyright (c) 2025 STMicroelectronics.
  * All rights reserved.
  *
  * This software is licensed under terms that can be found in the LICENSE file
  * in the root directory of this software component.
  * If no LICENSE file comes with this software, it is provided AS-IS.
  *
  ******************************************************************************
  */
/* USER CODE END Header */
/* Includes ------------------------------------------------------------------*/
#include "main.h"
#include "fdcan.h"
#include "icache.h"
#include "memorymap.h"
#include "usart.h"
#include "gpio.h"

/* Private includes ----------------------------------------------------------*/
/* USER CODE BEGIN Includes */
#include <stdio.h>
/* USER CODE END Includes */

/* Private typedef -----------------------------------------------------------*/
/* USER CODE BEGIN PTD */

/* USER CODE END PTD */

/* Private define ------------------------------------------------------------*/
/* USER CODE BEGIN PD */

/* USER CODE END PD */

/* Private macro -------------------------------------------------------------*/
/* USER CODE BEGIN PM */

/* USER CODE END PM */

/* Private variables ---------------------------------------------------------*/

/* USER CODE BEGIN PV */
__IO 	uint32_t PushButtonState = PB_NOT_PRESSED;
FDCAN_RxHeaderTypeDef RxHeader;
uint8_t RxData[8]={0,1,0,0,0,0,0,0};
FDCAN_TxHeaderTypeDef TxHeader;
uint8_t TxData[8]={0,0,0,0,0,0,0,0};
/* USER CODE END PV */

/* Private function prototypes -----------------------------------------------*/
void SystemClock_Config(void);
static void SystemPower_Config(void);
/* USER CODE BEGIN PFP */
void FDCAN_Config(void);
/* USER CODE END PFP */

/* Private user code ---------------------------------------------------------*/
/* USER CODE BEGIN 0 */
int _write(int fd, char *ptr, int len)
{
	HAL_UART_Transmit(&huart1, (unsigned char*)ptr, len, HAL_MAX_DELAY);
	return len;
}
/* USER CODE END 0 */

/**
  * @brief  The application entry point.
  * @retval int
  */
int main(void)
{

  /* USER CODE BEGIN 1 */

  /* USER CODE END 1 */

  /* MCU Configuration--------------------------------------------------------*/

  /* Reset of all peripherals, Initializes the Flash interface and the Systick. */
  HAL_Init();

  /* USER CODE BEGIN Init */

  /* USER CODE END Init */

  /* Configure the System Power */
  SystemPower_Config();

  /* Configure the system clock */
  SystemClock_Config();

  /* USER CODE BEGIN SysInit */

  /* USER CODE END SysInit */

  /* Initialize all configured peripherals */
  MX_GPIO_Init();
  MX_ICACHE_Init();
  MX_FDCAN1_Init();
  MX_USART1_UART_Init();
  /* USER CODE BEGIN 2 */
  FDCAN_Config();
  uint8_t buffer[256];
  sprintf((char *)buffer, "START!\r\n");
  HAL_UART_Transmit(&huart1, buffer, strlen((char *)buffer), 100);
  HAL_FDCAN_ActivateNotification(&hfdcan1, FDCAN_IT_TX_EVT_FIFO_NEW_DATA, 0);

  /* USER CODE END 2 */

  /* Infinite loop */
  /* USER CODE BEGIN WHILE */
  while (1)
  {	  __HAL_PWR_CLEAR_FLAG(PWR_FLAG_SBF);
      HAL_GPIO_WritePin(GPIOA, GPIO_PIN_5, 1);
      HAL_Delay(5000);
      HAL_GPIO_WritePin(GPIOA, GPIO_PIN_5, 0);
      HAL_GPIO_WritePin(GPIOA, GPIO_PIN_6, 0);
      PushButtonState = PB_NOT_PRESSED;

      uint8_t buffer[256];
      sprintf((char *)buffer, "Enter STOP2 MODE\r\n");
      HAL_UART_Transmit(&huart1, buffer, strlen((char *)buffer), 100);

      __HAL_RCC_PWR_CLK_ENABLE ();
      HAL_PWREx_EnterSTOP2Mode(PWR_SLEEPENTRY_WFI);
      SystemClock_Config();

      MX_FDCAN1_Init();
      FDCAN_Config();

      HAL_NVIC_ClearPendingIRQ(EXTI13_IRQn);
      HAL_NVIC_EnableIRQ(EXTI13_IRQn);
      while (PushButtonState == PB_NOT_PRESSED);
    /* USER CODE END WHILE */

    /* USER CODE BEGIN 3 */
  }
  /* USER CODE END 3 */
}

/**
  * @brief System Clock Configuration
  * @retval None
  */
void SystemClock_Config(void)
{
  RCC_OscInitTypeDef RCC_OscInitStruct = {0};
  RCC_ClkInitTypeDef RCC_ClkInitStruct = {0};

  /** Configure the main internal regulator output voltage
  */
  if (HAL_PWREx_ControlVoltageScaling(PWR_REGULATOR_VOLTAGE_SCALE3) != HAL_OK)
  {
    Error_Handler();
  }

  /** Initializes the CPU, AHB and APB buses clocks
  */
  RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_MSI;
  RCC_OscInitStruct.MSIState = RCC_MSI_ON;
  RCC_OscInitStruct.MSICalibrationValue = RCC_MSICALIBRATION_DEFAULT;
  RCC_OscInitStruct.MSIClockRange = RCC_MSIRANGE_4;
  RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
  RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_MSI;
  RCC_OscInitStruct.PLL.PLLMBOOST = RCC_PLLMBOOST_DIV1;
  RCC_OscInitStruct.PLL.PLLM = 1;
  RCC_OscInitStruct.PLL.PLLN = 32;
  RCC_OscInitStruct.PLL.PLLP = 2;
  RCC_OscInitStruct.PLL.PLLQ = 32;
  RCC_OscInitStruct.PLL.PLLR = 2;
  RCC_OscInitStruct.PLL.PLLRGE = RCC_PLLVCIRANGE_0;
  RCC_OscInitStruct.PLL.PLLFRACN = 0;
  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_CLOCKTYPE_PCLK3;
  RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_MSI;
  RCC_ClkInitStruct.AHBCLKDivider = RCC_SYSCLK_DIV1;
  RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV1;
  RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV1;
  RCC_ClkInitStruct.APB3CLKDivider = RCC_HCLK_DIV1;

  if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_0) != HAL_OK)
  {
    Error_Handler();
  }
}

/**
  * @brief Power Configuration
  * @retval None
  */
static void SystemPower_Config(void)
{

  /*
   * Switch to SMPS regulator instead of LDO
   */
  if (HAL_PWREx_ConfigSupply(PWR_SMPS_SUPPLY) != HAL_OK)
  {
    Error_Handler();
  }
/* USER CODE BEGIN PWR */
/* USER CODE END PWR */
}

/* USER CODE BEGIN 4 */
void HAL_GPIO_EXTI_Rising_Callback(uint16_t GPIO_Pin)
{  //SystemClock_Config();
  /* Prevent unused argument(s) compilation warning */
	if(GPIO_Pin == BTN_Pin)
		{
		PushButtonState = PB_PRESSED;
		printf("▶▶\r\n");
		if (HAL_FDCAN_AddMessageToTxFifoQ(&hfdcan1, &TxHeader, TxData) != HAL_OK)
		{
			printf("HAL_CAN_AddTxMessage error\r\n");
			HAL_Delay(100);
		}
		else
		{
			printf("HAL_CAN_AddTxMessage start\r\n");
			HAL_Delay(100);
		}


		}
}

void HAL_FDCAN_TxEventFifoCallback(FDCAN_HandleTypeDef *hfdcan, uint32_t TxEventFifoITs)
{
	printf("HAL_FDCAN_TxEventFifoCallback\r\n");
	 if (TxEventFifoITs & FDCAN_IT_TX_EVT_FIFO_NEW_DATA)
	    {
	        printf("HAL_CAN_AddTxMessage completed\r\n");
	    }
}

void HAL_FDCAN_RxFifo0Callback(FDCAN_HandleTypeDef *hfdcan, uint32_t RxFifo0ITs)
{
  if((RxFifo0ITs & FDCAN_IT_RX_FIFO0_NEW_MESSAGE) != RESET)
  {
    /* Retrieve Rx messages from RX FIFO0 */
    if (HAL_FDCAN_GetRxMessage(hfdcan, FDCAN_RX_FIFO0, &RxHeader, RxData) != HAL_OK)
    {
    Error_Handler();
    }
	  for(int i=0; i<TxHeader.DataLength; i++)
	  {
		  printf("RxData[%d] = %d\r\n", i, RxData[i]);
		  HAL_Delay(100);
	  }
  }
 }

void FDCAN_Config(void)
{
  FDCAN_FilterTypeDef sFilterConfig;
  hfdcan1.Init.AutoRetransmission = ENABLE;

  HAL_FDCAN_ConfigInterruptLines(&hfdcan1, FDCAN_IT_TX_EVT_FIFO_NEW_DATA, FDCAN_INTERRUPT_LINE0);
  HAL_FDCAN_ActivateNotification(&hfdcan1, FDCAN_IT_TX_EVT_FIFO_NEW_DATA, 0);


  /* Configure Rx filter */
  sFilterConfig.IdType = FDCAN_STANDARD_ID;
  sFilterConfig.FilterIndex = 0;
  sFilterConfig.FilterType = FDCAN_FILTER_RANGE;
  sFilterConfig.FilterConfig = FDCAN_FILTER_TO_RXFIFO0;
  sFilterConfig.FilterID1 = 0x321;
  sFilterConfig.FilterID2 = 0x7FF;
  if (HAL_FDCAN_ConfigFilter(&hfdcan1, &sFilterConfig) != HAL_OK)
  {
    Error_Handler();
  }

  /* Start the FDCAN module */
  if (HAL_FDCAN_Start(&hfdcan1) != HAL_OK)
  {
    Error_Handler();
  }

  if (HAL_FDCAN_ActivateNotification(&hfdcan1, FDCAN_IT_RX_FIFO0_NEW_MESSAGE, 0) != HAL_OK)
  {
    Error_Handler();
  }

  /* Prepare Tx Header */
  TxHeader.Identifier = 0x321;
  TxHeader.IdType = FDCAN_STANDARD_ID;
  TxHeader.TxFrameType = FDCAN_DATA_FRAME;
  TxHeader.DataLength = FDCAN_DLC_BYTES_2; //보낼 바이트 값 설정
  TxHeader.ErrorStateIndicator = FDCAN_ESI_PASSIVE;
  TxHeader.BitRateSwitch = FDCAN_BRS_OFF;
  TxHeader.FDFormat = FDCAN_CLASSIC_CAN;
  TxHeader.TxEventFifoControl = FDCAN_STORE_TX_EVENTS;
  TxHeader.MessageMarker = 0;

  HAL_FDCAN_Start(&hfdcan1);
}
/* USER CODE END 4 */

/**
  * @brief  This function is executed in case of error occurrence.
  * @retval None
  */
void Error_Handler(void)
{
  /* USER CODE BEGIN Error_Handler_Debug */
  /* User can add his own implementation to report the HAL error return state */
  __disable_irq();
  while (1)
  {
  }
  /* USER CODE END Error_Handler_Debug */
}

#ifdef  USE_FULL_ASSERT
/**
  * @brief  Reports the name of the source file and the source line number
  *         where the assert_param error has occurred.
  *   file: pointer to the source file name
  *   line: assert_param error line source number
  * @retval None
  */
void assert_failed(uint8_t *file, uint32_t line)
{
  /* USER CODE BEGIN 6 */
  /* User can add his own implementation to report the file name and line number,
     ex: printf("Wrong parameters value: file %s on line %d\r\n", file, line) */
  /* USER CODE END 6 */
}
#endif /* USE_FULL_ASSERT */

[mƎALLEm]

Hello,

Did you enable the NVIC FDCAN?

Also you didn't share your MX_FDCAN1_Init()!

Please in next time provide the exact part number of the STM32 MCU.