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FDCAN on NUCLEO-H743ZI

Question asked by Alberto Vignani on Oct 16, 2017
Latest reply on Feb 5, 2018 by ab val

I succeeded in transmitting CAN messages from my new Nucleo-H743 board (after adding the needed transceivers), but there are oddities.

I made a project with CubeMX, not using for the moment any FD feature, setting the CAN clock to 64MHz, the prescaler to 8 and the CAN timings to 9-4-3, as expected for generating a 500kHz signal; it didn't work.

With the help of an oscilloscope and some retries I determined that to get 500kHz I must set the prescaler to 16(?) and the CAN clock to 66MHz; with these settings the Canalyzer shows the messages without errors.

I suspect some problem in the Clock Calculator of CubeMX, but so far the generated code looks fine.

Can anyone explain this?

 

Alberto

 

Follow-up: I made a new CubeMX configuration from scratch, and this one makes more sense. Now there is an 8MHz input clock instead of the previous 25MHz (from where did it come?), and the FDCAN works with the 64MHz input clock. The only remaining oddity is that I still need to set its prescaler to 16 instead of the expected 8.

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