LPC546 MCAN TX FIFO mode

[Patrick88]

Hi, I'm using LPC54618 with mcan module. In SDK demos, there is only demos of sending can data with "dedicated buffers", while the real sending sequence is determined by CAN ID, But I need send CAN frames sequentially, as in a FIFO way.

I find there is "tx FIFO/queue" way of sending data, but no demos or APIs. Is there any demo or brief about how to use MCAN "tx FIFO/queue" method, or can anyone give me some tips. Thanks!

[Patrick88]

HI.@Raul,

Thank you for your advice, I've found a solution for my question.

①In MCAN initialization code, set TX FIFO configuration : 

    mcan_tx_buffer_config_t txBuffer =

    {

        .address = TX_BUFFER_OFS,

        .dedicatedSize = 0U,

        .fqSize = 32,

        .mode = kMCAN_txFifo,

        .datafieldSize = 64,

    };

②In application code :

uint8_t idx_arr[32];

uint8_t idx_idx;

bool MCAN_SendWithFifo(CAN_Type* base, mcan_tx_buffer_frame_t* tx)

{

    /*check if TX FIFO is full*/

    if(base->TXFQS & CAN_TXFQS_TFQF_MASK)

        return false;

    /*get TX FIFO put index*/

    uint8_t idx = ((base->TXFQS & CAN_TXFQS_TFQPI_MASK) >> CAN_TXFQS_TFQPI_SHIFT);

    idx_arr[idx_idx] = idx;

    idx_idx = (idx_idx+1)%32;

    mcan_buffer_transfer_t xfer =

    {

        .bufferIdx = idx,

        .frame = tx,

    };

    /*actually copy data to TX buffer, and add request to send message out*/

    status_t err = MCAN_TransferSendNonBlocking(base, CANFD_Channels[ch].CANHandle, &xfer);

    if(kStatus_Success == err)

        return true;

    else

        return false;

}

③In MCAN ISR code, as I use only TX FIFO and no TX BUFFER or TX QUEUE, I do the following change :

 

void MCAN_TransferHandleIRQ(CAN_Type *base, mcan_handle_t *handle)

{

...............................

        else if (0U != (valueIR & (uint32_t)kMCAN_TxTransmitCompleteFlag))

        {

            /* Solve Tx interrupt. */

            uint8_t idx = 0U;

            // for (; idx < (uint8_t)((base->TXBC & CAN_TXBC_NDTB_MASK) >> CAN_TXBC_NDTB_SHIFT); idx++)

            for(; idx < (uint8_t)((base->TXBC & CAN_TXBC_TFQS_MASK) >> CAN_TXBC_TFQS_SHIFT); idx++)

            {

                /* Get the lowest unhandled Tx Message Buffer */

                if (0U != MCAN_IsTransmitOccurred(base, idx))

                {

                    if ((base->TXBTIE & ((uint32_t)1U << idx)) != 0U)

                    {

                        MCAN_TransferAbortSend(base, handle, idx);

                    }

                }

            }

            result = (uint32_t)kMCAN_TxTransmitCompleteFlag;

            status = kStatus_MCAN_TxIdle;

        }

...............................

}

Above all, MCAN TX FIFO mode is now working. I think this solution is not good enough, but works for my project, hopefully someone can give a better one, or an official solution soon.

Thank You Again!

[RaRo · Accepted solution]

Hello @Patrick88,

Unfortunately, as you mention there is not an example to start with TX FIFO/QUEUE with MCAN module. Nonetheless, next we list information could be useful to take a look at:

• UM10912. LPC546xx User Manual. Chapter 35: LPC546xx Controller Area Network Flexible Data. Section 35.14.7. Tx handling

• If you are using LPCXpresso546x8/540xx/54S0xx Board in the UM1103. Board User Manual. It is mentioned than other example code could be found in OM13094 | LPCXpresso Development Board | LPC Microntrollers (MCUs) | NXP Semiconductors in Design Resources -> Software.

Best regards, Raul.

[Patrick88]

Hi.@Raul,

With your tips, I finally found a slotion as below.

①in MCAN initialization code, configure TX Buffer:

    mcan_tx_buffer_config_t txBuffer =

    {

        .address = TX_BUFFER_OFS,

        .dedicatedSize = 0U,

        .fqSize = 32,

        .mode = kMCAN_txFifo,

        .datafieldSize = 64,

    };

②in application code:

uint8_t idx_arr[32];

uint8_t idx_idx;

bool MCAN_SendWithFifo(CAN_Type* base, mcan_tx_buffer_frame_t* tx)

{

    /*check if TX FIFO is full*/

    if(base->TXFQS & CAN_TXFQS_TFQF_MASK)

        return false;

    /*get TX FIFO put index*/

    uint8_t idx = ((base->TXFQS & CAN_TXFQS_TFQPI_MASK) >> CAN_TXFQS_TFQPI_SHIFT);

    idx_arr[idx_idx] = idx;

    idx_idx = (idx_idx+1)%32;

    mcan_buffer_transfer_t xfer =

    {

        .bufferIdx = idx,

        .frame = tx,

    };

    /*actually copy data to TX buffer, and add request to send message out*/

    status_t err = MCAN_TransferSendNonBlocking(base, CANFD_Channels[ch].CANHandle, &xfer);

    if(kStatus_Success == err)

        return true;

    else

        return false;

}

③In MCAN ISR code, as I use TX FIFO only and no TX BUFFER or TX QUEUE, I did some change:

.................

        else if (0U != (valueIR & (uint32_t)kMCAN_TxTransmitCompleteFlag))

        {

            /* Solve Tx interrupt. */

            uint8_t idx = 0U;

            // for (; idx < (uint8_t)((base->TXBC & CAN_TXBC_NDTB_MASK) >> CAN_TXBC_NDTB_SHIFT); idx++)

            for(; idx < (uint8_t)((base->TXBC & CAN_TXBC_TFQS_MASK) >> CAN_TXBC_TFQS_SHIFT); idx++)

            {

                /* Get the lowest unhandled Tx Message Buffer */

                if (0U != MCAN_IsTransmitOccurred(base, idx))

                {

                    if ((base->TXBTIE & ((uint32_t)1U << idx)) != 0U)

                    {

                        MCAN_TransferAbortSend(base, handle, idx);

                    }

                }

            }

            result = (uint32_t)kMCAN_TxTransmitCompleteFlag;

            status = kStatus_MCAN_TxIdle;

        }

.................

Above all, mcan now works with TXFIFO mode, and sends messages sequentially. I think this solution is not good enough, but it works for my project, and hopefully someone can give a better solution or an official solution soon.

Thank you!

[Patrick88]

Thank.@Raul,

I will look into the files you mentioned above, and post the solution if I find any.