Seatalk Input alternative

[GerryB]

Since the Seatalk input does not function with the Rpi5, can it be alternatively used as another NMEA 0183 input? 
Thanks. G

[sebba]

I am thinking also about that.
as far as I know (and I am not very well documented) I saw the @signalk/signalk-autopilot is using a serial device for sending data to seatalk1
maybe with minor modifications will be able to provide an universal bidirectional interface with seatalk1.
still, is just an idea, the developer should know better.

At the same time, I saw this kind of bidirectional interface is somehow avoided and I am wondering why.
Even is old, seatalk1 is still present and still working on many boats.

[Adrian]

Repurposing the Seatalk1 input of the MacArthur HAT for NMEA 0183 won't work for two reasons:

1. the SeaTalk1 input of the MacArthur HAT excepts a +12V / GND signal swing, NMEA is only ~5 V / GND.
   
2. the open issue with Seatalk1 currently not working with Pi5 / OpenPlotter 4 is due to a deprecated GPIO library, you'd have the same issue for NMEA
   

Bi-directional Seatalk1 is a whole other can of worms. To do it properly, the sender must also listen while sending to detect collisions. This will require two GPIOs, plus software logic.

[Sailoog]

I am thinking also about that.
as far as I know (and I am not very well documented) I saw the @signalk/signalk-autopilot is using a serial device for sending data to seatalk1
maybe with minor modifications will be able to provide an universal bidirectional interface with seatalk1.
still, is just an idea, the developer should know better.

At the same time, I saw this kind of bidirectional interface is somehow avoided and I am wondering why.
Even is old, seatalk1 is still present and still working on many boats.

https://forum.openmarine.net/showthread.php?tid=5059

[GerryB]

Thanks for the replies. 

My boat is all Seatalk and NMEA 0183, with no NMEA 2000. The Raymarine ST4000+ Autohelm has a NMEA 0183 input port and makes the input data available to all devices on the Seatalk network, so I don't need to convert NMEA data to Seatalk. I have also got a Raymarine E85001 to convert Seatalk data to NMEA, so I don't need the Seatalk to NMEA function on the HAT either. 
 
Given that I have NMEA data coming in from four talkers, (GPS via USB, AIS from a dAISy receiver, Wind and boat speed from Seatalk via the E85001, and DSC data from the VHF radio) I could do with an extra NMEA 0183 input port on the Pi. Would a RS422 to USB adapter be a viable solution? 
Thanks.