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TMS320F280049C: CAN communication - F280049C

Fengyu Leng
Intellectual 1255 points
Part Number: TMS320F280049C
Other Parts Discussed in Thread: TMS320LF2406A

Tool/software:

Hi TI expert,

My customer use TMS320LF2406 and F280049 to communicate with the same CAN node. The node is special because its communicate rate is not stable, about 122kbps~128kbps.

F2406 and F280049's configuration are shown as below. Communication rate are 125kbps. Under this condition, they find F280049 will receive more error frame. We use calculation formula in F280049 TRM to calculate Oscillator Tolerance Range and F28004x has higher Oscillator Tolerance Range than F2406. So we can't understand why F280049 has more error frame. 

Could you please help explain why F2406 receive little error fame? And what I we do to decrease the number of F280049's error frame? Thanks

PN

CPU frequency

SJW

TSEG1

TSEG2

BRP

Tq

Bit-Time

Oscillator Tolerance Range

1

TMS320LF2406A

40

3

11

4

20

500ns

16

0.9375%

3

TMS320F28004x

100

4

9

6

50

500ns

16

1.25%

BR,

Fengyu

  • 0
    TI__Guru**** 192196 points

    Hi Fengyu,

    What is the bus error or message error? 

    Can you try to use the sample point for both node? Where sample point = (TSEG1+1)/(TSEG1+TSEG2+1)

    How long is the CAN bus?

  • 0 in reply to QJ Wang
    TI__Intellectual 1255 points

    Hi QJ,

    You can refer to below table. It shows that all types of CAN bus error occurs. Only the frames marked in Green are right frame.

    Then length of CAN bus is about 20m.

    Kindly ask,  why F2406A doesn't have so many error frame compared to F280049. It's Oscillator Tolerance Range smaller than F280049.

    BR,

    Fengyu

  • 0 in reply to Fengyu Leng
    TI__Guru**** 192196 points

    HI Fengyu,

    It's better to have the sample point as far back as possible. Typically the sample-point is given as a range such as 80%~90%. The sample-point is between the phase segment 1 and the phase segment 2 of a bit-time. 

    Your message shows that he sample-point at node F280049 is at 62.5%, and 75% at node F2406

    Can you use the same setting at both nodes:

    PN

    CPU frequency

    SJW

    TSEG1

    TSEG2

    BRP

    Tq

    Baudrate

    Bit-Time

    		 Sample Point

    1

    TMS320LF2406A

    40

    7

    30

    7

    8

    200ns

    125kbps

    40

    		 80%

    3

    TMS320F28004x

    100

    7

    30

    7

    20

    200ns

    125kbps

    40

    		 80%

    actual TSeg2 value = TSEG2 + 1, and actual TSeg1 value = TSEG1 + 1

  • 0 in reply to QJ Wang
    TI__Intellectual 1255 points

    Hi QJ, 

    Datasheet shows SJW can't surpass 4. Could you please help suggest other suitable settings? Thanks!

    BR,

    Fengyu

  • 0 in reply to Fengyu Leng
    TI__Guru**** 192196 points

    Hi Fengyu,

    You are correct. CAN_BTR register has only 2 bits for SJW, so its maximum SJW is (3+1).