FDCAN with BRS activated: Problem transmitting 64 Bytes on FDCAN

[GS1]

Hi all,

I am trying to use FDCAN with Baud rate switch (500 kB / 2 MBit) activated and I want to send 64 Byte.

Processor is STM32H7A3. Project was set up with CubeMX V. 6.11.1 and HAL FW_H7 V1.11.2. Clock for FDCAN is 80 MHz.

The problem is that the system only sends with 500 kB and 8 Bytes only.

I am transmitting the data to my PC using a PEAK USB dongle (FDCAN capable with BRS) and in parallel check the messages on a scope. 

I don't know, why it doesn't switch to 2 MBit and I only see  8 Bytes with 500 kBit on my scope and on PCAN-Explorer.

Here my init and transmit code sequences:

FDCAN_HandleTypeDef* phCan;

phCan = &hfdcan1;
phCan->Instance = FDCAN1;

phCan->Init.Mode = FDCAN_MODE_NORMAL; 
phCan->Init.FrameFormat = FDCAN_FRAME_FD_BRS;

phCan->Init.AutoRetransmission = ENABLE;   
phCan->Init.TransmitPause = DISABLE;

phCan->Init.NominalPrescaler = 10;
phCan->Init.NominalSyncJumpWidth = 1;
phCan->Init.NominalTimeSeg1 = 11;
phCan->Init.NominalTimeSeg2 = 4;

phCan->Init.DataPrescaler = 2;
phCan->Init.DataSyncJumpWidth = 1;
phCan->Init.DataTimeSeg1 = 14;
phCan->Init.DataTimeSeg2 = 5;

phCan->Init.MessageRAMOffset = 0;
phCan->Init.StdFiltersNbr = 0;
phCan->Init.ExtFiltersNbr = 0;

phCan->Init.RxFifo0ElmtsNbr = 16; // 0..64
phCan->Init.RxFifo1ElmtsNbr = 16;
phCan->Init.RxBuffersNbr = 10;

phCan->Init.RxFifo0ElmtSize = FDCAN_DATA_BYTES_64;
phCan->Init.RxFifo1ElmtSize = FDCAN_DATA_BYTES_64;
phCan->Init.RxBufferSize = FDCAN_DATA_BYTES_64;


phCan->Init.TxEventsNbr = 0;
phCan->Init.TxBuffersNbr = 0;

phCan->Init.TxFifoQueueElmtsNbr = 16;
phCan->Init.TxFifoQueueMode = FDCAN_TX_FIFO_OPERATION;

phCan->Init.TxElmtSize = FDCAN_DATA_BYTES_64;

phCan->msgRam.StandardFilterSA = 0;
phCan->msgRam.ExtendedFilterSA = 0;
phCan->msgRam.RxFIFO0SA = 0;
phCan->msgRam.RxFIFO1SA = 0;
phCan->msgRam.RxBufferSA = 0;
phCan->msgRam.TxEventFIFOSA = 0;
phCan->msgRam.TxBufferSA = 0;
phCan->msgRam.TxFIFOQSA = 0;
phCan->msgRam.TTMemorySA = 0;
phCan->msgRam.EndAddress = 0;
phCan->ErrorCode = 0;


halErr = HAL_FDCAN_Init(phCan);

halErr = HAL_FDCAN_Start(phCan);

----------------------------------

TxHeader.IdType = FDCAN_STANDARD_ID;
TxHeader.TxFrameType = FDCAN_DATA_FRAME;
TxHeader.ErrorStateIndicator = FDCAN_ESI_ACTIVE;

TxHeader.FDFormat = FDCAN_FRAME_FD_BRS;
TxHeader.BitRateSwitch = FDCAN_BRS_ON;

TxHeader.TxEventFifoControl = FDCAN_STORE_TX_EVENTS;//FDCAN_NO_TX_EVENTS;
TxHeader.MessageMarker = 0;

TxHeader.Identifier = 0x55;

TxHeader.DataLength = FDCAN_DLC_BYTES_64;

halErr = HAL_FDCAN_AddMessageToTxFifoQ(phfdcan, &TxHeader, TxData);  // TxData = 64 Bytes

Is there anything missing or wrong?

Thank you for any support or hints.

BR GS

Post edited by the ST moderator to follow the community rule especially for the code sharing.

[mƎALLEm · Accepted solution]

Hello,

First, please use </> button to share your code. Please refer to this post: How to insert source code

Second, what is your transceiver allowed bitrate bandwidth?

3rd, what is your clock source? HSI or a crystal?

4th, please call the following before the call of HAL_FDCAN_Start():

  /**
    * Configure and enable Tx Delay Compensation, required for BRS mode.
    * TdcOffset default recommended value: DataTimeSeg1 * DataPrescaler
    * TdcFilter default recommended value: 0
    */
  if (HAL_FDCAN_ConfigTxDelayCompensation(&hfdcan1, (hfdcan1.Init.DataPrescaler * hfdcan1.Init.DataTimeSeg1), 0U) != HAL_OK)
  {
    Error_Handler();
  }

  if (HAL_FDCAN_EnableTxDelayCompensation(&hfdcan1) != HAL_OK)
  {
    Error_Handler();
  }

[LCE]

Don't you need extended ID for BRS? 
So try IdType = FDCAN_EXTENDED_ID

Not sure though...

[GS1]

Hello,

thank you for your help:

- The transceiver is TCAN1042HG and can do up to 5 MBit 

- Clock source for the system is a Crystal 8 MHz, Clocksource for FDCAN is Clock Divider PLL2Q 

- I inserted your code suggestion. However the result is the same as before. Only 8 Byte with 500 kBit arrive

Any other ideas?

BR GS

[GS1]

Hi LCE,

I tried that, but that doesn't solve the problem. It only changes the ID presentation.

BR. GS

[mƎALLEm]

Could you please attach your project? (tomorrow I'm out of office)

[GS1]

Hello,

I am sorry, but I can not send the complete project. We are using our own custom board and the FDCAN part is now a with BRS is a new required feature.

Would the .IOC file be sufficient? Then you could include the posted initialisation and the send routine.

Meanwhile I will do some more trials with the latest HAL library, debugging (with Keil ULINKPro), to confirm, that the registers are treated correctly, etc. 

BR GS

[LCE]

You are setting:

TxHeader.FDFormat = FDCAN_FRAME_FD_BRS;

This is not a valid value, so probably resets TX to BRS off.
I guess you copied from init...

Try setting it to:

TxHeader.FDFormat = FDCAN_FD_CAN;

[GS1]

Hello LCE,

thank you for pointing this out. You are right! 

I tried that and now this at least changes the behaviour, but not in the direction I expected: Now it doesn't send at all in FDCAN Mode. FIFO gets full and HAL_ERROR is returned when sending further messages. 

I will keep on learning and trying...  

BR GS

[GS1]

Hello LCE,

thanks for your input!

Just want to give the current state of my FDCAN transmission trials:

- Send 64 Bytes in FDCAN mode without BRS: works at 500kBit!

- Send with ..BRS_ON (500k/2MBit): The system starts a transmission and puts the ID on the bus (seen on scope). Then nothing follows and (as I continuously send data in my test) I see that the next ID is sent immediately until FIFO is full (32 Messages) then nothing is sent to the bus anymore.

Can a wrong bit timing stop the transmitter to switch to the other bitrate and stop sending the data part?

What can cause the transmitter to stop after the ID? 

Any further hints very welcome.

BR GS