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CAN TX pin always high in NORMAL mode

MudKIP
Visitor

‎2024-11-30 03:42 PM

I'm trying to set up CAN in the Nucleo STM32H723 eval kit, I can see the message written to the CAN RAM, but I dont see any activity on the TX pin using an oscilloscope. The CAN is configured in NORMAL_MODE, I have testes before with EXTERNAL_LOOPBACK and I can receive messages on the same board, but I want to transmit it to the bus.

For now I only have the TX and RX pins, PD1 and PD0, respectively, they aren't connected to anything, not even a transceiver, nor terminating resistors but I assume I should still see something in the TX pin when I'm transmitting.

The code is the following:

 

/* Includes ------------------------------------------------------------------*/
#include "main.h"

FDCAN_HandleTypeDef hfdcan1;

// FDCAN1 Defines
FDCAN_TxHeaderTypeDef   TxHeader1;
FDCAN_RxHeaderTypeDef   RxHeader1;
uint8_t               TxData1[8] = {
		85,85,85,85,
		85,85,85,85
};
uint8_t               RxData1[8];

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

  /* USER CODE BEGIN 1 */
	// Configure TX Header for FDCAN1
	TxHeader1.Identifier = 0x55;
	TxHeader1.IdType = FDCAN_STANDARD_ID;
	TxHeader1.TxFrameType = FDCAN_DATA_FRAME;
	TxHeader1.DataLength = FDCAN_DLC_BYTES_8;
	TxHeader1.ErrorStateIndicator = FDCAN_ESI_ACTIVE;
	TxHeader1.BitRateSwitch = FDCAN_BRS_OFF;
	TxHeader1.FDFormat = FDCAN_FD_CAN;
	TxHeader1.TxEventFifoControl = FDCAN_NO_TX_EVENTS;
	TxHeader1.MessageMarker = 0;
  /* 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 clock */
  SystemClock_Config();

  /* USER CODE BEGIN SysInit */

  /* USER CODE END SysInit */

  /* Initialize all configured peripherals */
  MX_GPIO_Init();
  MX_FDCAN1_Init();
  /* USER CODE BEGIN 2 */


  if(HAL_FDCAN_Start(&hfdcan1)!= HAL_OK)
  {
   Error_Handler();
  }
  /* USER CODE END 2 */

  /* Infinite loop */
  /* USER CODE BEGIN WHILE */
  while (1)
  {
	  if (HAL_FDCAN_AddMessageToTxFifoQ(&hfdcan1, &TxHeader1, TxData1)!= HAL_OK)
	  {
	   Error_Handler();
	  }

	  HAL_Delay (1000);
    /* 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};

  /** Supply configuration update enable
  */
  HAL_PWREx_ConfigSupply(PWR_LDO_SUPPLY);

  /** Configure the main internal regulator output voltage
  */
  __HAL_PWR_VOLTAGESCALING_CONFIG(PWR_REGULATOR_VOLTAGE_SCALE0);

  while(!__HAL_PWR_GET_FLAG(PWR_FLAG_VOSRDY)) {}

  /** Initializes the RCC Oscillators according to the specified parameters
  * in the RCC_OscInitTypeDef structure.
  */
  RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSE;
  RCC_OscInitStruct.HSEState = RCC_HSE_BYPASS;
  RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
  RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSE;
  RCC_OscInitStruct.PLL.PLLM = 4;
  RCC_OscInitStruct.PLL.PLLN = 275;
  RCC_OscInitStruct.PLL.PLLP = 1;
  RCC_OscInitStruct.PLL.PLLQ = 4;
  RCC_OscInitStruct.PLL.PLLR = 2;
  RCC_OscInitStruct.PLL.PLLRGE = RCC_PLL1VCIRANGE_1;
  RCC_OscInitStruct.PLL.PLLVCOSEL = RCC_PLL1VCOWIDE;
  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_D3PCLK1|RCC_CLOCKTYPE_D1PCLK1;
  RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_PLLCLK;
  RCC_ClkInitStruct.SYSCLKDivider = RCC_SYSCLK_DIV1;
  RCC_ClkInitStruct.AHBCLKDivider = RCC_HCLK_DIV2;
  RCC_ClkInitStruct.APB3CLKDivider = RCC_APB3_DIV2;
  RCC_ClkInitStruct.APB1CLKDivider = RCC_APB1_DIV2;
  RCC_ClkInitStruct.APB2CLKDivider = RCC_APB2_DIV2;
  RCC_ClkInitStruct.APB4CLKDivider = RCC_APB4_DIV2;

  if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_3) != HAL_OK)
  {
    Error_Handler();
  }
}

/**
  * @brief FDCAN1 Initialization Function
  * @PAram None
  * @retval None
  */
static void MX_FDCAN1_Init(void)
{

  /* USER CODE BEGIN FDCAN1_Init 0 */

  /* USER CODE END FDCAN1_Init 0 */

  /* USER CODE BEGIN FDCAN1_Init 1 */

  /* USER CODE END FDCAN1_Init 1 */
  hfdcan1.Instance = FDCAN1;
  hfdcan1.Init.FrameFormat = FDCAN_FRAME_CLASSIC;
  hfdcan1.Init.Mode = FDCAN_MODE_NORMAL;
  hfdcan1.Init.AutoRetransmission = DISABLE;
  hfdcan1.Init.TransmitPause = DISABLE;
  hfdcan1.Init.ProtocolException = DISABLE;
  hfdcan1.Init.NominalPrescaler = 11;
  hfdcan1.Init.NominalSyncJumpWidth = 1;
  hfdcan1.Init.NominalTimeSeg1 = 17;
  hfdcan1.Init.NominalTimeSeg2 = 7;
  hfdcan1.Init.DataPrescaler = 25;
  hfdcan1.Init.DataSyncJumpWidth = 1;
  hfdcan1.Init.DataTimeSeg1 = 5;
  hfdcan1.Init.DataTimeSeg2 = 3;
  hfdcan1.Init.MessageRAMOffset = 0;
  hfdcan1.Init.StdFiltersNbr = 0;
  hfdcan1.Init.ExtFiltersNbr = 0;
  hfdcan1.Init.RxFifo0ElmtsNbr = 1;
  hfdcan1.Init.RxFifo0ElmtSize = FDCAN_DATA_BYTES_8;
  hfdcan1.Init.RxFifo1ElmtsNbr = 0;
  hfdcan1.Init.RxFifo1ElmtSize = FDCAN_DATA_BYTES_8;
  hfdcan1.Init.RxBuffersNbr = 0;
  hfdcan1.Init.RxBufferSize = FDCAN_DATA_BYTES_8;
  hfdcan1.Init.TxEventsNbr = 0;
  hfdcan1.Init.TxBuffersNbr = 0;
  hfdcan1.Init.TxFifoQueueElmtsNbr = 1;
  hfdcan1.Init.TxFifoQueueMode = FDCAN_TX_FIFO_OPERATION;
  hfdcan1.Init.TxElmtSize = FDCAN_DATA_BYTES_8;
  if (HAL_FDCAN_Init(&hfdcan1) != HAL_OK)
  {
    Error_Handler();
  }
  /* USER CODE BEGIN FDCAN1_Init 2 */

  /* USER CODE END FDCAN1_Init 2 */

}

 

and HAL_FDCAN_Init itself calls, which configures the TX and RX pins, PD1 and PD0 respectively. 

void HAL_FDCAN_MspInit(FDCAN_HandleTypeDef* hfdcan)
{
  GPIO_InitTypeDef GPIO_InitStruct = {0};
  RCC_PeriphCLKInitTypeDef PeriphClkInitStruct = {0};
  if(hfdcan->Instance==FDCAN1)
  {
  /* USER CODE BEGIN FDCAN1_MspInit 0 */

  /* USER CODE END FDCAN1_MspInit 0 */

  /** Initializes the peripherals clock
  */
    PeriphClkInitStruct.PeriphClockSelection = RCC_PERIPHCLK_FDCAN;
    PeriphClkInitStruct.FdcanClockSelection = RCC_FDCANCLKSOURCE_PLL;
    if (HAL_RCCEx_PeriphCLKConfig(&PeriphClkInitStruct) != HAL_OK)
    {
      Error_Handler();
    }

    /* Peripheral clock enable */
    __HAL_RCC_FDCAN_CLK_ENABLE();

    __HAL_RCC_GPIOD_CLK_ENABLE();
    /**FDCAN1 GPIO Configuration
    PD0     ------> FDCAN1_RX
    PD1     ------> FDCAN1_TX
    */
    GPIO_InitStruct.Pin = GPIO_PIN_0|GPIO_PIN_1;
    GPIO_InitStruct.Mode = GPIO_MODE_AF_PP;
    GPIO_InitStruct.Pull = GPIO_NOPULL;
    GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
    GPIO_InitStruct.Alternate = GPIO_AF9_FDCAN1;
    HAL_GPIO_Init(GPIOD, &GPIO_InitStruct);

  /* USER CODE BEGIN FDCAN1_MspInit 1 */

  /* USER CODE END FDCAN1_MspInit 1 */

  }

}

Note the use of 85 to see it clearly on the oscillsocope, but I am not getting anything on the TX line.
How is the message sent after it is written to RAM?
Thanks.

 

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