Hi@rexoplans
1. Have you configured and initialized the pins correctly?

2. If everything is configured correctly, then you can use tools such as an oscilloscope or logic analyzer to test whether the TX output on the MCU side has the correct output.
3. If the TX on the MCU side is normal, then solve the problem of TJA1055. Usually the STB and EN pins should be controlled by the MCU side.
Input requirements for STB and EN pins
