S32K3 How to change CAN bps online?

[Julián_AragónM]

Hi @EvaKi,

You can change the FlexCAN bitrate through the configuration in peripherals: 

Chapter 73.3.10.8.1 from the S32K3XX's Reference Manual explains the timing parameters required by the CAN protocol. You can also use the following community post for CAN bit timing calculation: MPC5xxx/S32Kxx/LPCxxxx: CAN / CAN FD bit timing calculation - NXP Community.

Best regards,
Julián

[EvaKi]

@Julián_AragónM Thanks for your response.

I know the method for changing CAN bps. For my issue is when I enable 500Kbps FlexCAN communication, I want to switch to 250Kbps. It was a failure. Even I re-init CAN driver.

That is what I say online. 

500Kbps work successfully, and switch to 250Kbps by a extra signal. It is failure

[Julián_AragónM]

Hi @EvaKi,

Chapter 73.6.2.3 Control 1 (CTRL1) from the Reference Manual specifies that these CAN bit timing variables can only be modified in freeze mode. They cannot be changed in runtime:

Best regards,
Julián

[EvaKi]

@Julián_AragónM 

Sorry for taking so long to reply

For changing CAN bps, I use the FreezeMode. but it can be only effect on rise CAN bps.

such as: 250Kbps -> 500Kbps， it is ok.

250Kbps -> 125Kbps, it's not ok

void can_SetBitrate( uint8_t bitrate )

{

FlexCAN_Disable( IP_CAN_0 );

FlexCAN_Ip_EnterFreezeMode_Privileged(INST_FLEXCAN_0);

FlexCAN_Ip_SetBitrate_Privileged(INST_FLEXCAN_0,&can_pall_config[bitrate],FALSE);

FlexCAN_Ip_ExitFreezeMode_Privileged(INST_FLEXCAN_0);

FlexCAN_Enable( IP_CAN_0 );

}

[Julián_AragónM]

Hi @EvaKi

Could you share if any bus error appears while measuring CAN bus? Is this a problem while debugging or does the transceiver stop sending data? Please share what is meant by "not ok".

Are you using a CAN to USB analyzer? Or is this two CAN nodes?

Best regards,
Julián