I have close to the same system and am doing the same thing. At the autopilot
i have a multifunctuon blah blah from raymarine. Open the cover and you see some terminals marked seatalk, on the ends there are a set for nmea 0183 in and out. I got my gps
signal here and is working fine, am having trouble getting ais to show on e120. I also have a px with rs422 connection that i bought an adapter from amazon for 10 bucks and plugged in and it has everything showing in open cpn
. So.....current track, i have oredered an rs232
connection and usb adapter to plug
it into laptop
to act as a mutiplexer. Total cost so far excluding ais is $28. I already had some extra wire.