CAN FD 8Mbps

[Tomato1]

On the evaluation board S32K3X4EVB-T172,

when the CAN FD transmission speed is increased from 4 Mbps to 5 or 8Mbps, the data phase waveform output stops. I would like to ask for advice on how to resolve this issue.

Data transmission is operating correctly in the range of 500 kbps to 4 Mbps.

The arbitration phase is 1 Mbps, and the payload is 64 bytes.

[Senlent]

Hi@Tomato1

My mistake.

I retested and discovered that I hadn't enabled BRS and Enhanced CBT before.

The attached results are based on the S32K344EVB.

I discovered that when the rate reaches 5MB, TDC configuration must be enabled; otherwise, communication will fail. (I didn't encounter any problems at 4MB.)

(The ETDCOFF value for TDC is a value I entered based on a simple test. Theoretically, it is related to the transceiver used and the bus architecture.)

[Tomato1]

Thank you for your response.

With the attached file, I was able to send at 8Mbps, but after about 100 seconds of continuous transmission, I am unable to exit the loop at the following line in the main function. I would appreciate your confirmation on this.

Despite having a transmission interval of about 1 second, the bit in register "IFAG1" is not set to 1, or it may have been inadvertently cleared.

while(FlexCAN_Ip_GetTransferStatus(INST_FLEXCAN_0, TX_MB_IDX) != FLEXCAN_STATUS_SUCCESS)

{

FlexCAN_Ip_MainFunctionWrite(INST_FLEXCAN_0, TX_MB_IDX);

}

[Senlent · Accepted solution]

Hi@Tomato1

I don't have a test environment to test at a rate of 8MB/s.

You can check the ESR register yourself to confirm possible causes of the error. This is likely still related to the TDC configuration value.

You'll have to spend some time troubleshooting this yourself. You can add a timeout check for transmission, and after the timeout, you can call "FlexCAN_Ip_AbortTransfer" to try retransmitting.

[Tomato1]

I changed the CAN transceiver from TJA1443 to TJA1462, which supports 8 Mbps, and retried. Up to 4 Mbps, transmission works normally, but when set to 5 Mbps, as shown in the image below, a waveform is transmitted for an instant, and then nothing is sent afterward. I would like to know the cause and how to resolve this.

At 5 Mbps, the waveform pattern changes midway.

[Senlent]

Hi@Tomato1

I can't test the 8MB for you, but I tested the 5MB on the S32K3X4EVB with your configuration, and it worked perfectly.

[Tomato1]

I have reviewed the attached file.

I was able to replicate the same operation,

but when checking the waveform with an oscilloscope, it shows a bit width of 1us, and the data phase appears to be transmitted at 1Mbps.

When setting "brs" to TRUE, the transmission stops midway through the waveform.

Please check it.

[Senlent]

Hi@Tomato1

TJA1443 is used in S32K3X4EVB-T172 and i can see the speed limited on TJA1443.

This could be the reason why 8Mbps can not run successfully.

[Tomato1]

Thank you for your response. I will replace the CAN transceiver with one that supports 8Mbps and try again.