PROCESSOR-SDK-J721S2: The problem of CAN sampling point deviation

Hello,

Based on sampling point calculation it seems to be correct for 80% sampling

 https://e2e.ti.com/support/processors-group/processors/f/processors-forum/920090/faq-tda4vm-can-how-is-bit-rate-calculated-for-can

I shall assign this to HW expert.

Regards

Tarun Mukesh

Hi, Tarun Mukesh

I will add a few phenomena that we investigated, hoping to help you analyze.
1. Check the corresponding register through CCS and find that parameters have been successfully written

2. We conducted a new round of test using the default parameters of SDK, and found that the test result was 81.875, which was too different from the 75 we set

Best regards，

Bingxian

Dear Tarun.

would you please help check latest post from bingxian? 

"using the default parameters of SDK, and found that the test result was 81.875"

for default parameters of SDK, sample time should be 75%. what about this on TI EVM?

thanks a lot!

yong

Dear Expert.

would you please help share the comment?

thanks a lot!

yong

Hi Yong,

Are you using bit rate switching?  Can you share the value of the MCAN_DBTP register?

Regards,

HAL

Hi HAL

We used CAN, we did not use CANFD.
The MCAN_DBTP register reads the following values:

Best regards，

Bingxian

Hi HAL

Our test method is as follows:

Using the VH6501 jamming device, a fixed message is sent while gradually modifying the bit width of a specific bit in the arbitration field to test the sampling point of the arbitration field.  Similarly, the bit width of a specific bit in the data field is gradually modified to test the sampling point of the data field.  By gradually reducing the bit width, it is possible to detect an error frame, thus identifying the sampling point.

Best regards，

Bingxian

Hi Bingxian，

  One note in the manual, " The bit rate configured for the CAN FD data phase via DBTP must be higher or equal to
the bit rate configured for the arbitration phase via NBTP" ,  currently, Setting DBTP to 16, NBTP to 25, obvisately, setting violates this provision. Please check and feedback.

  Thanks.

Linjun