topic Re: CAN is busy when transmit in S32K

CAN is busy when transmit

Johnson97 — Mon, 29 Dec 2025 13:55:53 GMT

Hi NXP Community,

I redirected the CanIf_RxIndication function. When setting the CAN module to the loopback mode, the test was successful and the transmitted and received data were consistent.

However, when I exited the loopback mode, I was unable to send the message and the Can_43_FLEXCAN_Write function returned 0x02 (busy).

The tx pin of the MCU was synchronized with the rx pin data and was not the expected data to be sent. The rx data was approximately 130ns slower than the tx data and was continuously occurring (it should send one frame roughly every second).

The transceiver is TJA1043. I have set the STB and EN pins to high. CANH and CANL have remained unchanged.

The following is the information of the ESR register. Please help to troubleshoot what the possible cause might be.

Thank you very much!

Re: CAN is busy when transmit

Senlent — Tue, 30 Dec 2025 02:21:06 GMT

Hi@Johnson97

Please share your project, and I will take some time to review it for you.

Re: CAN is busy when transmit

Johnson97 — Tue, 30 Dec 2025 02:56:20 GMT

Please check the attached file.The version of the RTD package is SW32K3_S32M27x_RTD_R21-11_4.0.0_P19_D2403

Re: CAN is busy when transmit

Senlent — Tue, 30 Dec 2025 03:23:40 GMT

Hi@Johnson97

Could you update your RTD to a newer version, or modify a test routine on your S32 DS so I can check it for you? (I haven't installed that RTD version yet.)

Re: CAN is busy when transmit

Johnson97 — Tue, 30 Dec 2025 03:33:38 GMT

Sorry, the Autosar package purchased for this project has specified the use of this version of RTD.

Therefore, I need to configure the mcal based on this version and verify that it is error-free.

Could you install this version and help me troubleshoot the issue?

Re: CAN is busy when transmit

Senlent — Tue, 30 Dec 2025 07:02:14 GMT

Hi@Johnson97

In the project you provided, your clock configuration is completely wrong.

Your FXOSC clock is 20MHz

The MFI your setting is 120,ODIV2 is 4, which is out of range of PLL VCO output frequency(240)

You must follow the requirement in the reference manual:

for your reference:

Finally, don't forget to reconfigure FlexCan's baudrate settings.

Re: CAN is busy when transmit

Johnson97 — Tue, 30 Dec 2025 11:01:19 GMT

Thank you very much. The problem has been solved.

Apart from the aforementioned issues, the configuration of the CAN baud rate-related registers also does not match the valid values specified in the manual.

The waveform of the tx pin of the MCU has met the expectations. The subsequent issues should be related to the transceiver.

Thank you again!