2021-08-29, 09:13 PM
(2021-08-28, 04:51 PM)Slovak Wrote:(2021-07-15, 08:40 PM)Techstyle Wrote: it seems like manufacturers are not specific about polarity on the NMEA0183 connection so try:
PI VHF
TX(+) --> RX(+)
TX(-) --> RX(-)
RX(+) --> TX(+)
RX(-) --> TX(-)
if that doesn't work, swap the polarity:
PI VHF
TX(+) --> RX(-)
TX(-) --> RX(+)
RX(+) --> TX(-)
RX(-) --> TX(+)
this worked for me on both a Raymarine autopilot and a Garmin Chartplotter.
After about a week of beating my head against the wall with the PICAN-M HAT on my RPi4, I swapped the polarity per your suggestion and everything suddenly started to work. Interestingly, this is true for anemometer as well as VHF - which makes me wonder whether the board may be mislabeled or it's just general confusion amongst manufacturers. Either way, got it all working - thank you!
No problem, this seems like a common thing which leads me to believe that it is a NMEA0183 vs RS422 issue rather than mislabeling. My Seatalk 1 Autopilot and my Garmin communicate fine with the same polarity, it is the connection to the Pi (RS422) that is inverted.