To see the waveform until the ACK phase, a transceiver must be connected to the
node. Without a transceiver, the node immediately goes into an error state.
Check if the CAN frame is correctly seen at the MCANTX pin of the transmitting
MCU and it is of the expected bit-rate. If the expected data is seen at the
MCANTX pin, check the data at the MCANRX pin. If the same data is seen at the
MCANRX pin, the transceiver is correctly looping back the data.
If using an oscilloscope with a built-in CAN FD trigger, make sure that the
signal configured for triggering matches the signal being probed on the board.
Many oscilloscopes are capable of triggering on CAN-transmit (CANTX),
CAN-receive (CANRX), CAN_H and CAN_L signals, in addition to Start-of_Frame
(SOF), Remote frames, Error frames and specific MSGIDs.
If the scope does not decode the waveform, make sure input threshold value for
the channel is correct. This is similar to the “trigger level” that is normally
used for signals.
Make sure the bit-rate for both nominal and data phases are correctly configured
in the oscilloscope. Otherwise, it will show incorrect data.
CAN bus analyzer tool: Make sure bit-rate for both nominal and data phases are
correctly configured.