STM32C542RCT6 CANFD is not working with internal clock

[harishDST]

Hi,

I am working on CAN FD communication using the STM32C542RCT6. CAN FD is working properly when I use an external clock source. However, when I switch to the internal clock, the controller starts reporting errors such as Error Passive, followed by Bus-Off.

My suspicion is that the internal clock may have a slight frequency deviation, which could be affecting CAN FD communication. Since this is a new controller, I would like to understand whether the internal clock can reliably support CAN FD communication or whether an external clock is required.

My current CAN FD configuration is:

• Arbitration bit rate: 500 kbps

• Data bit rate: 2 Mbps

• Bit Rate Switching (BRS): Enabled

Could you please clarify whether the internal clock can support this configuration and what could cause the controller to enter Error Passive and Bus-Off states when using it?

[Andrew Neil]

when I switch to the internal clock, the controller starts reporting errors

That is to be expected:

 

My suspicion is that the internal clock may have a slight frequency deviation

So look at the datasheet - the accuracy will be specified there.

Then you can check if it meets CAN’s accuracy requirements ...

[LCE]

The internal clock / HSI is only usable for basic operation and some “slow” or clocked interfaces.

For CAN, audio, ethernet and some other peripherals: never ever use HSI.