• State
  • Locked Locked
  • Replies 8 replies
  • Subscribers 82 subscribers
  • Views 439 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

Original question:

TMS320F28388D: CAN-FD not working at some rate combinations.

TMS320F28388D: About Normal 1MHz, Data 4MHz communication in CAN-FD

O.H
Mastermind 6480 points
Part Number: TMS320F28388D
Other Parts Discussed in Thread: TMDSCNCD28388D, C2000WARE

Tool/software:

Hi experts,

My customer is using F28388D (TMDSCNCD28388D) for evaluation, and I would like to confirm some things about Normal 1MHz, Data 4MHz communication in CAN-FD.

Q1: Are the following register settings no problem?

    bitTimingParams.dataRatePrescalar  = 0x0U; // Data Baud Rate Pre-scaler.
    bitTimingParams.dataTimeSeg1 = 0x7U; // Data Time segment before SP
    bitTimingParams.dataTimeSeg2 = 0x0U; // Data Time segment after SP
    bitTimingParams.dataSynchJumpWidth = 0x0U; // Data SJW

Q2: Is 5MHz the maximum bit rate for the Data section for CAN-FD?
Currently, they are using 40MHz, which is System 200MHz divided by 5.
The maximum frequency does not seem to be defined in the data sheet or TRM.

[Details]
The CAN communication pin of the TMDSCNCD28388D is connected to a CAN transceiver, and the CanBus is not connected to any other devices, only a termination resistor.
The CanBus CANH signal is observed with an oscilloscope.

The values ​​set with reference to the sample code "mcan_ex9_transmit.c" in C2000WARE and "MCAN_BitTimingCalculator.xls" are shown below, but it seems that only the Norm part is sent and the Data part is not sent.

    bitTimingParams.dataRatePrescalar  = 0x0U; // Data Baud Rate Pre-scaler.
    bitTimingParams.dataTimeSeg1       = 0x4U; // Data Time segment before SP
    bitTimingParams.dataTimeSeg2       = 0x3U; // Data Time segment after SP
    bitTimingParams.dataSynchJumpWidth = 0x3U; // Data SJW

After adjusting the sampling point with Cut-and-Try using the thread below, communication was possible when dataTimeSeg1 + dataTimeSeg2 = 7.
:e2e.ti.com/.../tms320f28388d-can-fd-not-working-at-some-rate-combinations

However, since the ideal value for 1 bit at 4MHz is 250ns, when only dataTimeSeg1 was changed to 0-6, the Data part was not sent.
When dataTimeSeg1 = 8, the Data part is sent, but it is 300ns.

[Waveform]

Normal 1MHz, Data 2MHz

Normal 1MHz, Data 4MHz[BitTimingCalculator]

Normal 1MHz, Data 4MHz[Manual]

If there is a problem with the setting value or the approach to adjusting the register value is incorrect, please let us know.

Best regards,
O.H

  • 0
    Mastermind 6480 points

    Hi experts,

    I received additional information from a customer, so I would like to share it.

    Just to be sure, I would appreciate an answer to Q1 and Q2.

    Q3: Are there any problems with the register values ​​below?
    Pre = 0x0U, TSeg1 = 0x18U, TSeg2 = 0x4U, SJW = 0x4U
    They are using the calculation formula in the following thread, not the  "MCAN_BitTimingCalculator.xls".
    :e2e.ti.com/.../faq-tda4vm-can-how-is-bit-rate-calculated-for-can

    They sets CAN_CLK=100MHz and recalculated the value in C2000 with the tool.
    The result is the following value.

    Pre = 0x0U, TSeg1 = 0x11U, TSeg2 = 0x11U, SJW = 0x10U

    However, with the above settings, the data section was not sent, and communication was successful(250ns=4MHz) with the settings of Q3.
    It doesn't work well with the  "MCAN_BitTimingCalculator.xls", so if there are any other more appropriate calculation methods, please let me know.

    Normal 1MHz, Data 4MHz[Manual with E2E]

    By the way, regarding Q2, if CAN_CLK = 200 MHz, 200 ns (5 Mbps) was achieved.

    Best regards,
    O.H

  • 0 in reply to O.H
    TI__Guru**** 197596 points

    Hi,

    Q1: the data baudrate = 40MHz / (seg1 + seg2 + 3) = 40/(7+0+3) = 4Mbps.

    O.H said:
    Q2: Is 5MHz the maximum bit rate for the Data section for CAN-FD?

    Yes. MCAN CAN FD supports data baud-rate up to 5 Mbps and a payload size of up to 64 bytes per frame.

    O.H said:
    Pre = 0x0U, TSeg1 = 0x11U, TSeg2 = 0x11U, SJW = 0x10U

    Please refer to DBTP register. The maximum TSEG2 is 0xF. Your setting (0x11) is out of the valid range.

  • 0 in reply to QJ Wang
    Mastermind 6480 points

    Hi QJ Wang,

    Thank you for your reply.

    Sorry my mistake.
    The yellow highlights below are the corrected parts.
    Could you please comment again if there are any problems?

    Q3: Are there any problems with the register values ​​below?
    Pre = 0x0U, TSeg1 = 0x12, TSeg2 = 0x4, SJW = 0x4
    They are using the calculation formula in the following thread, not the  "MCAN_BitTimingCalculator.xls".
    :e2e.ti.com/.../faq-tda4vm-can-how-is-bit-rate-calculated-for-can

    They sets CAN_CLK=100MHz and recalculated the value in C2000 with the tool.
    The result is the following value.

    Pre = 0x0U, TSeg1 = 0xB, TSeg2 = 0xB, SJW = 0xA

    Best regards,
    O.H

  • 0 in reply to O.H
    TI__Guru**** 197596 points

    Hi OH,

    I assume that Tseg1 and Tseg2 are the values programmed to CAN register

    For TSeg1=0x12, Tseg2=0x4, the sample point is (1+Tseg1+1)/(Tseg1+Tseg2 + 3) = 20/25 = 80%

    But 

    For Seg1 = 0xB, TSeg2 = 0xB, the sample point is (1+11+1)/25 = 56%

    Ideally, the bit time segments should be configured so that the sample point is as late as possible in the bit.

  • 0 in reply to QJ Wang
    Mastermind 6480 points

    Hi QJ Wang,

    Sorry for the late reply.

    I understood. We will contact you again if the customer has any additional questions.

    Best regards,
    O.H

  • 0 in reply to O.H
    TI__Guru**** 197596 points

    Hi O.H.,

    Did your customer run a test with TMDSCNCD28388D card which doesn't have a CAN transceiver?

  • 0 in reply to QJ Wang
    Mastermind 6480 points

    Hi QJ Wang,

    O.H said:
    [Details]
    The CAN communication pin of the TMDSCNCD28388D is connected to a CAN transceiver, and the CanBus is not connected to any other devices, only a termination resistor.
    The CanBus CANH signal is observed with an oscilloscope.

    The above is the environment.

    Best regards,
    O.H

  • 0 in reply to O.H
    TI__Guru**** 197596 points

    O.H,

    If the transmitter loop delay is > the dataTimeSeg1, the TDC should be enabled, and TDCO/TDCF need to be programmed. The recommended sample point is >75%, or 80%.