STM32H745 FDCAN Clock Frequency

jgauthier · ‎2022-05-27

Greetings,

I've been using FDCAN on STM32G0B boards at 64Mhz. I'm trying to configure an STM32H745 and it seems that the maximum clock frequency for FDCAN is 50MHz?

50Mhz itself is a very strange frequency and bitrates cannot be solved well using this frequency.

With some clock tweaking I was able to get it to 48Mhz. But I wasn't able to send/receive on my FDCAN network (I'm not sure if that is related)

Just looking for some thoughts on that. I am going to try 32Mhz next.

SofLit · ‎2022-05-30

This is where to choose the voltage scale in CubeMx:

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SofLit · ‎2022-05-30

Hello,

According the pop-up you provided, I think you're in VOS3.

According to the reference manual RM399 rev3/Table 61 Kernel clock distribution overview, FDCAN kernel clock should not exceed 50MHz when the voltage scale is in VOS3:

So in order to have higher kernel frequency for FDCAN please select higher Voltage scale in RCC menu and choose the right system frequency that matches your voltage scale.

Also be careful about choosing the timing parameters. Please refer to this thread.

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SofLit · ‎2022-05-30

This is where to choose the voltage scale in CubeMx:

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jgauthier · ‎2022-05-31

Ah, thank you! I was able to set this to VOS2, and set the frequency to 64Mhz. Now communication is working.

SofLit · ‎2022-05-31

Thank you for the feedback.

Could you please mark the answer that resolved your issue by selecting "Select as best". This will help other users find that answer faster.

Thank you.

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KennyD · ‎2024-11-26

Hi:

I'm new to using STM32 processors. I have a board with a STM32H745BIT3 processor. I'm having an extremely difficult time getting an initial FDCAN project configured. I'd like it to communicate with a laptop that uses a USB PEAK CAN FD adapter. The laptop will be running PEAKPCAN View. I have not been successful converting single core based ioc files to an ioc file for my H745 initial project. Any help would be greatly appreciated.

SofLit · ‎2024-11-26

Hello @KennyD ,

As this thread has been closed, I invite you to open a new thread on which you describe your request.

Also you need to describe in details what you need to achive, bitrate? CAN classic? CAN FD?

And you need to share your board schematics especially the CAN part. You need for sure an external Crystal for CAN communication.

Thank you.

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