Autohelm 2000 wiring diagram serial#

I also connected this directly to esp32 serial ports using 5/3.3 voltage level converter but this gives me also only FF FF. Voltage between GND and Rx or Tx is ~4,6V. Problem now is that I donвЂ™t know what are settings for serial communication and it should be reverse engineered.Дoes anyone have any advices how I could solve these sent commands from control unit or for the first step find out the communication protocol? I have tested almost all baud rates and serial communication settings but without success. ItвЂ™s impossible to recognize the commands as my reader is constantly giving FF FF. I had possibility to do this as course computer supports 5 control units.ДЄll I can see on bus is just FF FF and when I press buttons sometimes it gives me totally random HEX values. I connected control units to course computer and as well my USB-Serial ( This) to one of the slots to record all data moving between course computer and control unit. Now however, I have not got really far with my project. This way I could replace the control unit totally and even build modern nmea2000 support to the autopilot. After this I would build arduino setup to send exactly the same commands to course computer. So my plan was to connect these Rx and Tx to arduino and press all the buttons and see what commands it is sending. The brain in the control unit is NEX D8749HC ( Datasheet). I assume the communication between controller and computer is some kind of serial communication as I can see markings Rx and Tx. I took case off from the control unit and I can see that it has four cables going to course computer (Red +5, Black GND, Green Rx, Blue Tx). (I have items connected that are marked with blue)

I have completely replaced course computer with new one so I expect problem to be in control unit. Autopilot вЂњlogicвЂќ consists of Course computer and control units. This is really annoying feature when you are in the middle of sea. I have old Raymarine Autohelm 6000 autopilot (Pre SeaTalk version) which is every now and then freezing.

I tought here could be knowledge and willingness to push me to correct direction. After about three long evenings without success I would need some help on my project.