openplotter-gpio app can only get data from seatalk 1 devices.
If I am not wrong those ST2000 devices have seatalk 1 in/out but they also have NMEA 0183. If this is true you have just to connect a cheap USB-RS422 converter and configure OpenCPN.
EDIT
Ops sorry I did not read your device does not have NMEA
If I am not wrong those ST2000 devices have seatalk 1 in/out but they also have NMEA 0183. If this is true you have just to connect a cheap USB-RS422 converter and configure OpenCPN.
EDIT
Ops sorry I did not read your device does not have NMEA