I am trying to evaluate the FDCAN function on a STM32U5 and somehow I don't manage to make it work .
I can receive a frame when I am in (external) loop back mode and if the FDCAN transmits the frame but I cannot receive a frame in normal mode from an external source.
They are not Acknowledged.
I think I can exclude the CAN ID filter since the loopback mode is working fine .
Physically I can measure using an oscillosope that the frame is there with the expected boudrate and expected format (Standard CAN frame not FD frame.)
Also Using the external loopback function I can confirm that the Baudrate inside the controller is corectly configured
I can also see in the TEST Reg the RX pin toggling when the CAN connection is made .
Later Edit :
I can also confirm that the frame that I am trying to sent looks the same (Same timings + Same CRCs etc) if I am sending it using the CAN interface available or with the STM32U575 with External Loopback .
It seems that somethig between the phisical RX pin and the FDCAN itself . I have checked also the generated code regarding pin configuration . Both are correctly configured. (Tx is even working since I can measure the frame with the oscilloscope .). The frames are basically not received when they are coming from the RX pin itself. Is there any "low lower mode" feature that I need to activate / deactivate ?(Since U series is meant has a lot of low power new features)
