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TMS320F280039C: Operating MCAN module at 1 Mbps nominal and 5 Mbps data bit rates

Rishab Anand
Prodigy 30 points
Part Number: TMS320F280039C
Other Parts Discussed in Thread: C2000WARE

Tool/software:

I am trying to operate the MCAN module on an F280039C MCU at 1 Mbps nominal and 5 Mbps data bit rates. I am having trouble spotting the correct settings to do so. 

The MCAN module clock prescaler is set to 3.

I am able to get a nominal baud rate of 1 Mbps using the following settings

I am able to operate correctly at 2.5 Mbps using the setting below. 

I am trying to get a data baud rate of 5 Mbps by setting the data rate prescaler to 0 above. However, I do not see any message transmission attempts on the bus (using a scope to watch the CANH/CANL pins) if I make that change. I also tried changing the MCAN clock prescalar to do so but to no avail. 

Can somebody please verify if I am using valid settings ? 

  • 0
    TI__Guru**** 193286 points

    several comments for choosing TSeg1 and TSeg2:

    1. The bit time segments (TSeg1, TSeg2) should be configured so that the sample point is as late as possible in the bit. The sample point = (1 + TSeg1)/(1 + TSeg1 + TSeg2)

    2. The TSeg2 may not be shorter than any CAN controller’s Information Processing Time, which is device dependent and can be in the range of [0 … 2] tq

    3. SJW defines how far the resynchronizing mechanism may move the sample point inside the limits. It should not be 0

    Can you try those settings:

    MCAN module clock prescaler: /2 

    Nominal:

    prescaler:  2

    TSEG1: 14

    TSEG2: 3

    SJW: 3

    Data:

    prescaler: 0

    TSEG1: 7

    TSEG2: 2

    SJW: 2

  • 0 in reply to QJ Wang
    Prodigy 30 points

    Thanks for pointing out the issue with SJW. I tried using the recommended settings but I still see the same issue - no CAN transmit attempts. 

  • 0 in reply to Rishab Anand
    TI__Guru**** 193286 points

    Hi Rishab,

    Have you enabled the TDC (transmission delay compensation)? TDC is disabled by default. After it is enabled, please program TDCO and TDCF.

    I recommend TDCO=TDCF=data TSEG1

  • 0 in reply to QJ Wang
    TI__Guru**** 193286 points

    Hi Rishab,

    I tested 5Mbps data baudrate on a F28x device, it works as expected.

    My config is listed in below for CPU speed = 150MHz (For F280039, the CPU speed is 120MHz):

    /**********************************************/

    SysCtl_setMCANClk(SYSCTL_MCANA, SYSCTL_MCANCLK_DIV_3); //MCAN_CLK=50MHz

    /* baudrate = 50MHz/(0x4+0xe+3)(0x4+1)= 500kbps*/
    bitTimes.nomRatePrescalar = 0x4U; // Nominal Baud Rate Pre-scaler
    bitTimes.nomTimeSeg1 = 0x0EU; // Nominal Time segment before SP
    bitTimes.nomTimeSeg2 = 0x3U; // Nominal Time segment after SP
    bitTimes.nomSynchJumpWidth = 0x3U; // Nominal SJW


    /* baudrate = 50MHz/(0x6+1+3)(0x0+1)= 5000kbps*/
    bitTimes.dataRatePrescalar = 0x0U; // Data Baud Rate Pre-scaler
    bitTimes.dataTimeSeg1 = 0x6U; // Data Time segment before SP
    bitTimes.dataTimeSeg2 = 0x1U; // Data Time segment after SP
    bitTimes.dataSynchJumpWidth = 0x1U; // Data SJW

    initParams.emulationEnable = 0x1; //Added by QJ
    initParams.tdcEnable = 0x1U;         //Transmitter Delay Compensation enabled

    The PCAN receives all the messages transmitted by F28x MCAN node:

    The PCAN CAN-FD settings:

  • 0 in reply to QJ Wang
    TI__Guru**** 193286 points

    You can not get 2.5Mbps baudrate using the parameters in your 1st message. The actualk baudrate is: 40MHz/3/(3+1+3)= 40/21 mbps

    Please use the timing parameters below for test. 

    SysCtl_setMCANClk(SYSCTL_MCANCLK_DIV_2);  //MCAN clock = 60MHz

    bitTimes.nomRatePrescalar = 0x5U;   // Nominal Baud Rate Pre-scaler
    bitTimes.nomTimeSeg1 = 14U;           // Nominal Time segment before SP
    bitTimes.nomTimeSeg2 =   3U;           // Nominal Time segment after SP
    bitTimes.nomSynchJumpWidth = 0x3U; // Nominal SJW

    /* baudrate = 60/1/(8+1+3) = 5mbps*/
    bitTimes.dataRatePrescalar = 0x0U; // Data Baud Rate Pre-scaler
    bitTimes.dataTimeSeg1 = 0x8U; // Data Time segment before SP
    bitTimes.dataTimeSeg2 = 0x1U; // Data Time segment after SP
    bitTimes.dataSynchJumpWidth = 0x1U; // Data SJW

     and 

    initParams.emulationEnable = 0x1; 
    initParams.tdcEnable = 0x1U;         //Transmitter Delay Compensation enabled

    //
    // Transmitter Delay Compensation parameters.
    //
    initParams.tdcConfig.tdcf = 0xAU;
    initParams.tdcConfig.tdco = 0x9U;

    I am sorry the parameters I gave you is for different CPU clock.

  • 0 in reply to QJ Wang
    Prodigy 30 points

    Hi QJ,

    I was able to resolve this with your parameter set. I believe the issue was most likely due to transmission delay compensation not being enabled. MCAN example 13 on C2000ware 5.02 (mcan_ex13_transmit_TxEventFIFO) sets the compensation parameters without actually ever enabling the delay compensation itself. 

    I copied over the same example and was under the impression that the compensation is enabled. 

  • 0 in reply to QJ Wang
    Prodigy 30 points

    Thanks a lot once again for all these inputs. A small addition - the parameter set above gets the MCAN to work at 500 kbps nominal and 5 Mbps data rates. I changed the nominal baud rate prescalar to 2 from the 5 recommended above to get the MCAN to work at 1 Mbps nominal and 5 Mbps data rates. 

  • 0 in reply to Rishab Anand
    TI__Guru**** 193286 points

    Nice, thank you!