Is HWInitFunction redundant?

[hraftery]

As highlighted in this example, HWInitFunction should be set to CubeMX's CAN hardware initialisation function. But what for? The CubeMX generated code already calls the function (as the example neatly shows). The setting only seems to be used to call it again during CO_CANmodule_init(), which is called by CANopenNode's CO_CANinit(). Is this redundant? Is there another use case?

I ask, because the function is typically file scoped to main.c. I don't want to expose it wider if I don't have to.

[TheCitrusMan]

The thing with the CubeMX generated initialization is that you end up with a fixed bit rate. This may not be desirable. In my project on a STM32G0B1, I need the bit rate and node ID to be configurable at run time. To obtain this, I disabled the CubeMX generated initialization code by putting #if 0 #endif in the "user code" sections. This way the original initialization code, while still being (re)generated by CubeMX, will always be optimized away by the compiler...

/* FDCAN1 init function */
void MX_FDCAN1_Init(void)
{
    /* USER CODE BEGIN FDCAN1_Init 0 */

    /* USER CODE END FDCAN1_Init 0 */

    /* USER CODE BEGIN FDCAN1_Init 1 */
    // disabled!
#if 0
    /* USER CODE END FDCAN1_Init 1 */
    hfdcan1.Instance = FDCAN1;
    hfdcan1.Init.ClockDivider = FDCAN_CLOCK_DIV1;
    hfdcan1.Init.FrameFormat = FDCAN_FRAME_CLASSIC;
    hfdcan1.Init.Mode = FDCAN_MODE_NORMAL;
    hfdcan1.Init.AutoRetransmission = ENABLE;
    hfdcan1.Init.TransmitPause = ENABLE;
    hfdcan1.Init.ProtocolException = DISABLE;
    hfdcan1.Init.NominalPrescaler = 16;
    hfdcan1.Init.NominalSyncJumpWidth = 2;
    hfdcan1.Init.NominalTimeSeg1 = 13;
    hfdcan1.Init.NominalTimeSeg2 = 2;
    hfdcan1.Init.DataPrescaler = 1;
    hfdcan1.Init.DataSyncJumpWidth = 1;
    hfdcan1.Init.DataTimeSeg1 = 1;
    hfdcan1.Init.DataTimeSeg2 = 1;
    hfdcan1.Init.StdFiltersNbr = 0;
    hfdcan1.Init.ExtFiltersNbr = 0;
    hfdcan1.Init.TxFifoQueueMode = FDCAN_TX_FIFO_OPERATION;
    if (HAL_FDCAN_Init(&hfdcan1) != HAL_OK)
    {
        Error_Handler();
    }
    /* USER CODE BEGIN FDCAN1_Init 2 */
#endif
    /* USER CODE END FDCAN1_Init 2 */
}

Next, I created a custom init function with a bit rate parameter:

/* USER CODE BEGIN 1 */
/* FDCAN1 init function */
void CO_FDCAN1_Init(uint8_t baud)
{
    const uint32_t nominal_prescaler[] =
    {
        400, // index 0 = 10 kBaud
        200, // index 1 = 20 kBaud
        80, // index 2 = 50 kBaud
        40, // index 3 = 100 kBaud
        32, // index 4 = 125 kBaud
        16, // index 5 = 250 kBaud
        8, // index 6 = 500 kBaud
        5, // index 7 = 800 kBaud
        4 // index 8 = 1 MBaud
    };

    if (baud >= sizeof(nominal_prescaler) / sizeof(nominal_prescaler[0]))
    {
        Error_Handler();
    }

    hfdcan1.Instance = FDCAN1;
    hfdcan1.Init.ClockDivider = FDCAN_CLOCK_DIV1;
    hfdcan1.Init.FrameFormat = FDCAN_FRAME_CLASSIC;
    hfdcan1.Init.Mode = FDCAN_MODE_NORMAL;
    hfdcan1.Init.AutoRetransmission = ENABLE;
    hfdcan1.Init.TransmitPause = ENABLE;
    hfdcan1.Init.ProtocolException = DISABLE;
    hfdcan1.Init.NominalPrescaler = nominal_prescaler[baud];
    hfdcan1.Init.NominalSyncJumpWidth = 2;
    hfdcan1.Init.NominalTimeSeg1 = 13;
    hfdcan1.Init.NominalTimeSeg2 = 2;
    hfdcan1.Init.DataPrescaler = 1;
    hfdcan1.Init.DataSyncJumpWidth = 1;
    hfdcan1.Init.DataTimeSeg1 = 1;
    hfdcan1.Init.DataTimeSeg2 = 1;
    hfdcan1.Init.StdFiltersNbr = 0;
    hfdcan1.Init.ExtFiltersNbr = 0;
    hfdcan1.Init.TxFifoQueueMode = FDCAN_TX_FIFO_OPERATION;
    if (HAL_FDCAN_Init(&hfdcan1) != HAL_OK)
    {
        Error_Handler();
    }
}

/* USER CODE END 1 */

This function is then called near the end of the canopen_app_init() function in CO_app_STM32.c and will only be called once after reset. I want my stack to have configurable bit rate and node ID and have put these parameters in an SDO record in the PERSIST_COM section, which seemed like the easiest way as I haven't figured out how to use LSS yet. I put the code there as this is where the PERSIST_COM data has been restored from the EEPROM...

// Global variables
bool firstRun = true;


/* This function will basically setup the CANopen node */
int canopen_app_init(CANopenNodeSTM32 *_canopenNodeSTM32)
{
    // Keep a copy global reference of canOpenSTM32 Object
    canopenNodeSTM32 = _canopenNodeSTM32;

....
....

    if (firstRun)
    {
        // set baud rate and node ID based on stored information
        // only after reset
        CO_FDCAN1_Init(OD_PERSIST_COMM.x2000_COMM_params.baud_rate);
        canopenNodeSTM32->desiredNodeID = OD_PERSIST_COMM.x2000_COMM_params.node_id;

        firstRun = false;
    }

    canopen_app_resetCommunication();
    return 0;
}

There may be better / more elegant ways to do this but it works for me 🙂
Of course you have to take care to update your custom initialization code if you change anything to the configuration of the CAN periperal...

[TheCitrusMan]

Now that I'm looking at this again, it might be better to point canopenNodeSTM32.HWInitFunction to my custom initialization routine CO_FDCAN1_Init and then call it from within canopen_app_init(&canopenNodeSTM32) 🤔

That would be the "more elegant" way I guess...

[hraftery]

Nice use case. But yeah, there's still some work required to make use of HWInitFunction.

[TheCitrusMan]

You're right, it is not just a matter of filling the function in and be done with it. I'll leave it like it is for now 🙂