S32 Flexcan CanFd baud rate is equal to 1M/4M, send failed！

[chenms2004]

Hi, Hello!

        Recently, I was debugging the flexcan module CanFd  driver。 When the PE clock is 40MHZ, the Flexcan module can work normally when the baud rate is 1M(Sampling point : 60%)/2.5M(Sampling point : 75%), but when the baud rate is 1M(Sampling point : 60%)/4M(Sampling point :60%), The third-party equipment has no data reception。 We don't understand the reason; The specific register configuration is as follows:

(1)Baud rate = 1M/2.5M configuration   : 

    EPRESDIV=3u, ERJW=1u，EPROPSEG=1u，EPSEG1= 2u, EPSEG2=3u;(Sampling point : 60%)

    FPRESDIV=1u, FRJW=1u，FPROPSEG=3u，FPSEG1= 1u, FPSEG2=1u; (Sampling point : 75%)

(2)Baud rate = 1M/4M configuration   : 

    EPRESDIV=3u, ERJW=1u，EPROPSEG=1u，EPSEG1= 2u, EPSEG2=3u;(Sampling point : 60%)

    FPRESDIV=0u, FRJW=1u，FPROPSEG=2u，FPSEG1= 2u, FPSEG2=3u;(Sampling point : 60%)

Looking forward to your reply, thank you!

[Senlent]

Hi@chenms2004

        I did a test on S32K142EVB. when the maximum data bit rate reaches 3.5M, my PCAN-USB Pro can still receive messages, but it is unsuccessful when it reaches 4MBit/s(data bit rate).

        And I found that this problem should be the cause of the UJA1169 chip.

UJA1169 Mini high-speed CAN system basis chip

  And please refers to S32K RM: 55.5.10 Clock domains and restrictions

Table 55-34. Maximum CAN bit rate in data phase on CAN FD frames

 So, please check you CAN Phy,  user must ensure the bit time setting are in compliance with the CAN protocol standard.

BR!

       Jim,