RPi and OpenCPN - Multiplexer required?

[Island_Moose]

If I can connect to my existing onboard instruments (nmea0183) via an RS485-USB adaptor directly to a Rpi running OpenCPN, do I need an addtional multiplexer hat or unit? In other words, can OpenCPN multiplex multiple nmea sources in both directions?

I have a full set of B&G instruments including an ACP autopilot computer, but it's old (H1000) and the chartplotter is old and no longer supported.

I have discovered how to access the Fastnet system (Universal Interface) to send and receive data.

I want to install a RPi with an AIS hat and a 10" touchscreen. I want to pull data from the wind, magnetic, depth, speed instruments, add AIS and GPS, battery and solar monitors, and use all of this to display at the nav station and helm, as well as control the APilot.

John

[Dsanduril]

Originally Posted by Island_Moose

If I can connect to my existing onboard instruments (nmea0183) via an RS485-USB adaptor directly to a Rpi running OpenCPN, do I need an addtional multiplexer hat or unit? In other words, can OpenCPN multiplex multiple nmea sources in both directions?...

Short answer, yes. But this really depends on what hardware you will be multiplexing to. NMEA 0183 only allows a single talker on the wire, so is all your data on one wire (well, one pair of wires)? Then it can all come in on one USB interface.

How about going out? Is it all on one wire? Or is it going out by network?

In OpenCPN you configure a connection and can select "Output on this connection". You can filter the sentences that get output. You can use the NMEA converter plugin to aggregate data or create new sentences. You can output on serial or on the network.

You can also do pretty much all of the above in SignalK.

Our own system has three USB interfaces; two for incoming NMEA 0183 data (instruments and AIS/GPS) and one for outgoing data (all data except AIS to autopilot). I've done it solely in OpenCPN and in SignalK (the advantage to SignalK is that it runs as a service/daemon so people can't accidentally close it).

Draw up a sketch of how you envision the data will flow and that will help a lot.

[Island_Moose]

Originally Posted by Dsanduril

Short answer, yes. But this really depends on what hardware you will be multiplexing to. NMEA 0183 only allows a single talker on the wire, so is all your data on one wire (well, one pair of wires)? Then it can all come in on one USB interface.

How about going out? Is it all on one wire? Or is it going out by network?

In OpenCPN you configure a connection and can select "Output on this connection". You can filter the sentences that get output. You can use the NMEA converter plugin to aggregate data or create new sentences. You can output on serial or on the network.

You can also do pretty much all of the above in SignalK.

Our own system has three USB interfaces; two for incoming NMEA 0183 data (instruments and AIS/GPS) and one for outgoing data (all data except AIS to autopilot). I've done it solely in OpenCPN and in SignalK (the advantage to SignalK is that it runs as a service/daemon so people can't accidentally close it).

Draw up a sketch of how you envision the data will flow and that will help a lot.

Attached is a diagram of what I am proposing. Note the B&G H1000 system uses a proprietary comms system called Fastnet, which can be accessed through a single point (the Universal Interface). This is one Rx and Tx pair that carries ALL of the nmea 0183 (version 2.1?) sentences.