IMX8MP CAN FD test failed at a data bitrate of 6000k.

[charleshuang]

Hi NXP Team

Our customer tested CAN bus FD, and the test failed.

They tried setting the data bitrate to 6000k, but it failed.

However, setting the data bitrate to 5000k passed.

Do you have any advice?

Test command:  (Test 6000k Fail.)

ip link set can0 up type can bitrate 1000000 dbitrate 6000000  fd on

ip link set can1 up type can bitrate 1000000 dbitrate 6000000  fd on

Test 5000k pass.

[kef2 · Accepted solution]

Your customer shouldn't ignore "bitrate error 4,7%" message. As you see, he doesn't have such error with 5Mbps.
You can't use every bit rate you wish, but only those, which your CAN clock allows. You didn't specify what is your CAN clock. With 80MHz 8, 5, 4, 3.2, 2.5, 1.6, 1Mbps are possible plus those below 1Mbps. With 40MHz 3.2 is not possible, perhaps 1.6 as well, must check. For 6Mbps I guess you need 30 or 60MHz clock, try calculating it yourself.

[charleshuang]

Hi  @kef2 

We followed the NXP i.MX8MP DTSI settings, where the CAN clock is set to 40 MHz.

Do you know what the maximum bitrate value could be test pass?

Thanks.

[kef2]

Hi,

I think I wrote already, @40MHz CAN clock, 8Mbps is achievable. The most close speeds are 5 and 8Mbps, no more speeds in between @40Mhz.

Please don't forget as well capabilities of transceiver chips, you are using. 

[charleshuang]

@kef2 

Thanks about your help.  8Mbps pass.

[Rita_Wang]

Which version BSP are you using? Are you using NXP evk board or the board you design youself?

[charleshuang]

@Rita_Wang 

About our Image OS is Yocto 3.0-5.4.70.