TMDSCNCD28388D: CM CAN communication problem

rick sun

Prodigy 10 points

Part Number: TMDSCNCD28388D
Other Parts Discussed in Thread: C2000WARE, TMDSHSECDOCK,

Tool/software:

Hi,

We are currently running the CAN example for the CM from the template located at:

C:\ti\c2000\C2000Ware_5_03_00_00\driverlib\f2838x\examples\cm\can.

We didn't change anything, and the CAN bus bit rate was set to 500kHz (as default). However, it didn't communicate with the PeakCAN monitor. We then used an oscilloscope to monitor the CAN TX pin and found that the actual bitrate was 520kHz.

When we changed the bit rate as shown below, the PeakCAN started communicating, but the oscilloscope showed the actual bitrate to be 488kHz:

“CAN_setBitRate(CANA_BASE, CM_CLK_FREQ, 485000, 16);”

Could you please help us resolve this issue?

Thanks a lot,

Rick

over 1 year ago

0 Joseph Casuga over 1 year ago

TI__Mastermind 38830 points

Hi Rick,

Can you confirm which hardware you were running this with? Is it the control card or do you have a custom F28388x board? Also, were you able to run example can_config_c28x first to ensure that CM core is clocked at 125MHz?

Thanks,

Joseph

0 rick sun over 1 year ago in reply to Joseph Casuga

Prodigy 10 points

Thanks Joseph for your reply,

The hardware I am using is the F2838x full-featured evaluation kit (TMDSCNCD28388D and TMDSHSECDOCK).

Yes, I always run can_config_c28x first and then run CM one.

Best Wishes,

Rick

0 Joseph Casuga over 1 year ago in reply to rick sun

TI__Mastermind 38830 points

Hello Rick,

Just to be sure, can you please scope out the F2838x_25MHZ_CLK signal and see if you measure exactly 25MHz on this node?

Thanks you,

Joseph

0 rick sun over 1 year ago in reply to Joseph Casuga

Prodigy 10 points

Hi Joseph,

The F2838x_25MHZ_CLK signal (TP6 on the board) was measured at 25.0 MHz.

Best Wishes,

Rick

0 Joseph Casuga over 1 year ago in reply to rick sun

TI__Mastermind 38830 points

Hi Rick,

Thanks for validating the main clock on your setup. You can increase the bit time to get the baud rate closer to 500Kbps. Instead of using bit time of 16 in the function call:

CAN_setBitRate(CANA_BASE, CM_CLK_FREQ, 500000, 16);

Use

CAN_setBitRate(CANA_BASE, CM_CLK_FREQ, 500000, 20); instead.

Regards,

Joseph

0 rick sun over 1 year ago in reply to Joseph Casuga

Prodigy 10 points

Thanks Joseph,

I set bit time of 25 as below, and it works.

CAN_setBitRate(CANA_BASE, CM_CLK_FREQ, 500000, 25);

Thanks a lot for your help.

Best Wishes,

Rick

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TMDSCNCD28388D: CM CAN communication problem