Hi I am trying to connect hmi display with esp8266
The hmi display is already connected to controller board Till now i have figured out that there are 6 wires connecting hmi display and controller from those 6 wires 2 are VCC and 2 are GND rest 2 have negative voltage -5.56.So i have tried to connect it using Rs232 to ttl converter but getting 00 HEX value when connecting ttl to usb with the converter(on serial monitor) .Could anyone please help to figure out why negative voltage is used in between and how can i convert those signal to ttl so that i can read the signals transferred between the hmi and controller pcb.
Thanks,