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I have a complete instrument system (B&G) running nmea 0183.  My chartplotter/command computer is old and the charts are no longer available.  I can access this data through a universal interface.  I want to bring this data to a RPi, combine it with AIS, and then use it to run Openplotter and feed information back to my autopilot computer.

I know that I need a RPi, probably Kplex, an AIS hat or commercial AIS receiver....but I don't understand the best way to move the data around.

Should I buy a wifi multiplexer ($$) and connect that to the universal interface?  

Or can I just connect the interface to the RPi with a serial-usb cable?
The AIS receiver will need a will my GPS antenna.  Can you have 3 usb data feeds into the RPi?  

Will the RPi act put out a wifi data signal that I could then use on a tablet?

The thing is, multiplexers (wifi or not) are expensive.  I'd rather hard wire the RPi to the interface and let the RPi do the multiplexing if that's possible.  

Ultimately I'd like to have all of my nmea018 instruments reporting to the RPi, along with AIS, GPS, engine data, battery/solar charging data, and my tank levels.  I want to display all of this on a 10" screen in the cabin and a smaller screen at the helm.  Additionally, I'd love to broadcast this data over wifi so I can keep a tablet in the bunk for keeping anchor watch etc.

I know it's possible but I don't know how to move the data around.



New Zealand

My proposed system at the moment, using a hard-wired multiplexer.
if you haven't already done it you should be able to buy a usb to RS422 adapter to bring in NMEA0183 from your B&G unit. the GPS antenna can be a USB unit (I use a BU-353 unit). AIS can either by an RTL-SDR or something like a dAISy AIS receiver.

make sure you have a powered USB hub.

Nav station Monitor I am using a 10.1" 1080P monitor from Amazon -

I am working on getting a 13" waterproof/sunlight readable monitor for the helm
I am not sure how far your along with your install. I have been using different MUX,  WiFi and combined units made by a guy here in Australia for a couple of years now. I have found them to be very reliable and his back up warranty and support is very good. 

Here are a couple of units you may be able to make use of, these units are very affordable when compared to those items made by the bigger European company's.

2 Port NMEA MUX to WiFi Bridge allows you to connect 2 separate NMEA devices and transmit your NMEA data to all of your WiFi devices. I have used one of these to send AIS and Seatalk data (after conversion in the ST->NMEA) to my Pi. I powered the units off the seatalk bus as the current draw is very low. I cant imagine you will need the ST->NMEA I just mentioned how I set up to give you an idea.

Bi-Directional NMEA to WiFi Bridge allows you to transmit your NMEA data and it can also receive NMEA sentences back.

YakMUX 3 Port NMEA 0183 Combiner MUX with USB, allows different combinations of input and out put speed etc of NMEA data. 
When or if you want the wired data to and from the MUX for input to the PI there are several different RS422 or RS485 converters on Ebay and prices start at $5 

Check out the WIFi and MUX units here

I bought the Yakmux unit. I have yet to get it talking to OpenCPN, mainly because I had an electrical short with my B&G instrument system and had to replace a hub. When it was working I was able to see the GPS information streaming in on one port but nothing from the instruments on the other. I am confident I have it wired correctly because I've been working with Yakbitz directly, but I may not have the OpenCPN connection correct. I will make more attempts tonight and grab some screenshots. My Yakmux is connected to the Rpi with a USB cable.

Here's my connection to the B&G Universal Interface (all nmea data) and the GPS antenna.
Attached are 2 puTTy files showing the difference between when I connect the GPS antenna only, and then the B&G instruments.
looks like lots of corruption in the bgonly data, could be wiring or baud rate maybe?
(2021-10-20, 11:41 AM)PaddyB Wrote: [ -> ]looks like lots of corruption in the bgonly data, could be wiring or baud rate maybe?

Yes, i would check with the B&G first to get it working.

The GPS looks normal.

But why are the 2 mixed? I use an own NMEA-USB module for every Device. Maybe it is possible to read the TX with more Recievers (RX), but
NOT the other way around. So get these cheap USB-Serial plus an little USB-Hub and have it all seperated.