STM32H743ZI Nucleo seems unable to transmit via FDCAN 2?

Question

I am currently trying to send messages via both of my FDCAN transmitters on my Nucleo. But I am only able to transmit via FDCAN1 (classic master) and not via FDCAN 2 (classic slave).

The configuration setup is the same, only FDCAN1 starts sending , while FDCAN 2 gets a buffer overflow after a short time and never sends anything. I am monitoring with CANoe, where I can only see the message send via FDCAN1.

I also know it is not a hardware issue, since I changed my cables and the board and the problem remained the same. My cables are also terminated correctly...

Is there anything obvious I am missing?

Here is my code, I used CubeMx for the first initialisation.

The fdcan.c File: `

FDCAN_HandleTypeDef hfdcan1;
FDCAN_HandleTypeDef hfdcan2;
 
/* FDCAN1 init function */
void MX_FDCAN1_Init(void)
{
 
  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.NominalPrescaler = 5;
  hfdcan1.Init.NominalSyncJumpWidth = 1;
  hfdcan1.Init.NominalTimeSeg1 = 11;
  hfdcan1.Init.NominalTimeSeg2 = 4;
  hfdcan1.Init.DataPrescaler = 1;
  hfdcan1.Init.DataSyncJumpWidth = 1;
  hfdcan1.Init.DataTimeSeg1 = 1;
  hfdcan1.Init.DataTimeSeg2 = 1;
  hfdcan1.Init.MessageRAMOffset = 0;
  hfdcan1.Init.StdFiltersNbr = 0;
  hfdcan1.Init.ExtFiltersNbr = 0;
  hfdcan1.Init.RxFifo0ElmtsNbr = 8;
  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 = 8;
  hfdcan1.Init.TxFifoQueueMode = FDCAN_TX_FIFO_OPERATION;
  hfdcan1.Init.TxElmtSize = FDCAN_DATA_BYTES_8;
  hfdcan1.msgRam.StandardFilterSA = 0;
  hfdcan1.msgRam.ExtendedFilterSA = 0;
  hfdcan1.msgRam.RxFIFO0SA = 0;
  hfdcan1.msgRam.RxFIFO1SA = 0;
  hfdcan1.msgRam.RxBufferSA = 0;
  hfdcan1.msgRam.TxEventFIFOSA = 0;
  hfdcan1.msgRam.TxBufferSA = 0;
  hfdcan1.msgRam.TxFIFOQSA = 0;
  hfdcan1.msgRam.TTMemorySA = 0;
  hfdcan1.msgRam.EndAddress = 0;
  hfdcan1.ErrorCode = 0;
  if (HAL_FDCAN_Init(&hfdcan1) != HAL_OK)
  {
    _Error_Handler(__FILE__, __LINE__);
  }
}
/* FDCAN2 init function */
void MX_FDCAN2_Init(void)
{
 
  hfdcan2.Instance = FDCAN2;
  hfdcan2.Init.FrameFormat = FDCAN_FRAME_CLASSIC;
  hfdcan2.Init.Mode = FDCAN_MODE_NORMAL;
  hfdcan2.Init.AutoRetransmission = DISABLE;
  hfdcan2.Init.TransmitPause = DISABLE;
  hfdcan2.Init.NominalPrescaler = 5;
  hfdcan2.Init.NominalSyncJumpWidth = 1;
  hfdcan2.Init.NominalTimeSeg1 = 11;
  hfdcan2.Init.NominalTimeSeg2 = 4;
  hfdcan2.Init.DataPrescaler = 1;
  hfdcan2.Init.DataSyncJumpWidth = 1;
  hfdcan2.Init.DataTimeSeg1 = 1;
  hfdcan2.Init.DataTimeSeg2 = 1;
  hfdcan2.Init.MessageRAMOffset = 0;
  hfdcan2.Init.StdFiltersNbr = 0;
  hfdcan2.Init.ExtFiltersNbr = 0;
  hfdcan2.Init.RxFifo0ElmtsNbr = 8;
  hfdcan2.Init.RxFifo0ElmtSize = FDCAN_DATA_BYTES_8;
  hfdcan2.Init.RxFifo1ElmtsNbr = 0;
  hfdcan2.Init.RxFifo1ElmtSize = FDCAN_DATA_BYTES_8;
  hfdcan2.Init.RxBuffersNbr = 0;
  hfdcan2.Init.RxBufferSize = FDCAN_DATA_BYTES_8;
  hfdcan2.Init.TxEventsNbr = 0;
  hfdcan2.Init.TxBuffersNbr = 0;
  hfdcan2.Init.TxFifoQueueElmtsNbr = 16;
  hfdcan2.Init.TxFifoQueueMode = FDCAN_TX_FIFO_OPERATION;
  hfdcan2.Init.TxElmtSize = FDCAN_DATA_BYTES_8;
  hfdcan2.msgRam.StandardFilterSA = 0;
  hfdcan2.msgRam.ExtendedFilterSA = 0;
  hfdcan2.msgRam.RxFIFO0SA = 0;
  hfdcan2.msgRam.RxFIFO1SA = 0;
  hfdcan2.msgRam.RxBufferSA = 0;
  hfdcan2.msgRam.TxEventFIFOSA = 0;
  hfdcan2.msgRam.TxBufferSA = 0;
  hfdcan2.msgRam.TxFIFOQSA = 0;
  hfdcan2.msgRam.TTMemorySA = 0;
  hfdcan2.msgRam.EndAddress = 0;
  hfdcan2.ErrorCode = 0;
  if (HAL_FDCAN_Init(&hfdcan2) != HAL_OK)
  {
    _Error_Handler(__FILE__, __LINE__);
  }
}`

and the relevant part of the main.c:

uint8_t TxData[8] = {0xAA, 0xAA, 0xAA, 0xAA, 0xAA, 0xAA, 0xAA, 0xAA};
 
uint8_t TxData2[8] = {0xAA, 0xAA, 0xAA, 0xAA, 0xAA, 0xAA, 0xAA, 0xAB};
uint32_t msgerror=0;
uint32_t msgerror1=0;
/* USER CODE END PV */
 
/* Private function prototypes -----------------------------------------------*/
void SystemClock_Config(void);
static void MX_NVIC_Init(void);
      
 
/**
  * @brief  The application entry point.
  *
  * @retval None
  */
int main(void)
{
 
  /* 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_FDCAN1_Init();
  MX_FDCAN2_Init();
 
  /* Initialize interrupts */
  MX_NVIC_Init();
  /* USER CODE BEGIN 2 */
    
    TxHeader.Identifier = 0x120;
  TxHeader.IdType = FDCAN_STANDARD_ID;
  TxHeader.TxFrameType = FDCAN_DATA_FRAME;
  TxHeader.DataLength = FDCAN_DLC_BYTES_8;
  TxHeader.ErrorStateIndicator = FDCAN_ESI_ACTIVE;
  TxHeader.BitRateSwitch = FDCAN_BRS_OFF;
  TxHeader.FDFormat = FDCAN_CLASSIC_CAN;
  TxHeader.TxEventFifoControl = FDCAN_NO_TX_EVENTS;
  TxHeader.MessageMarker = 0;
    
    HAL_FDCAN_Start(&hfdcan1);
    HAL_FDCAN_Start(&hfdcan2);
  /* USER CODE END 2 */
 
  /* Infinite loop */
  /* USER CODE BEGIN WHILE */
  while (1)
  {
        
         if (HAL_FDCAN_AddMessageToTxFifoQ(&hfdcan2, &TxHeader, TxData) != HAL_OK)
            {
                /* Transmission request Error */
                msgerror++;
            }
            if (HAL_FDCAN_AddMessageToTxFifoQ(&hfdcan1, &TxHeader, TxData2) != HAL_OK)
            {
                /* Transmission request Error */
                msgerror1++;
            }
 
        HAL_Delay(100);     
 
  }

Answer 1

After finding the right data sheet, I found the solution. In the configuration for FDCAN2 I need to implement an offset:

 hfdcan2.Init.MessageRAMOffset = sizeof(hfdcan1);

After implementing this change transmit and receive are working without problem.