FDCAN not working on STM32H503CBT6

AUJVV · ‎2025-08-20

Hi,

I'm trying to communicate two microcontrollers (STM32H503CBT6 and a NUCLEO-H503RB) via FDCAN but the STM32H503CBT6 is not sending any messages.

Both have the same configuration, but the NUCLEO-H503RB can send (I have checked it with an oscilloscope).

Searching for an answer I found this question on the forum, saying that the STM32U5F7 has the FDCAN disabled by hardware and I wonder if this is the case with the STM32H503CBT6

Question: https://community.st.com/t5/stm32-mcus-products/fdcan-not-working-with-stm32u5f7/td-p/720224

Thanks!

Karl Yamashita · ‎2025-08-20

We know that a NUCLEO-H503RB is a development board but what is a STM32H503CBT6?

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CAN Jammer an open source CAN bus hacking tool

AUJVV · ‎2025-08-26

It is the 48 pin microcontroller from STM32H5 series.

Ozone · ‎2025-08-26

> I'm trying to communicate two microcontrollers (STM32H503CBT6 and a NUCLEO-H503RB) via FDCAN but the STM32H503CBT6 is not sending any messages.

> Both have the same configuration, but the NUCLEO-H503RB can send (I have checked it with an oscilloscope).

Have you checked the CAN Rx input at what you call "STM32H503CBT6" with a scope while the other side sends ?
And if so, what do the REC and TEC registers in the "STM32H503CBT6" CAN peripheral say ?

Karl Yamashita · ‎2025-08-26

@AUJVV wrote:

It is the 48 pin microcontroller from STM32H5 series.

So it's just the microcontroller by itself and not soldered onto a custom board?

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CAN Jammer an open source CAN bus hacking tool

MHoll.2 · ‎2025-08-26

the STM32H503CBT6 has a working FDCAN controller.

To help You I need more information:

1) The Nucleo-H503RB don't has a CAN Transceiver, can You show how You connected the CANBus?

2) How is the CANBus connected on You custom board (base on the STM32H503CBT6)?

AUJVV · ‎2025-08-27

I'm using the 2 transceivers TCAN1463-Q1 of Texas Instruments, one for the nucleo board and another for the custom board, same connection.

I was able to transmit with the custom board, but the signal looks like this:

I searched and I found out that this is probably due to the TX line, but I don't know what is causing it.

Have you ever encountered behaviour like this?

I'm clousing the post because i think that the problem is in my board.

mƎALLEm · ‎2025-08-27

Check your HW especially the transceiver part:

Power supply (VCC), VIO pin level voltage, EN pin, Standby pin level voltage etc..:

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