Moving From Ardupilot to PX4

i’m trying to port custom board that is running on Ardupilot to pixhawk, but I’m having issue with that… the FMU is based on STM32F765VI and i’m trying for 3 weeks now to make it work but nothing is moving… i tried to use the FMU_V5 as a base but couldn’t make it work (I’m not even able to bring the Serial console to work)

if anyone who did that and can direct me ill be grateful