NMEA 0183 Wiring Vesper Cortex to C80 chartplotter

[Nick J]

I'm installing a Vesper Cortex AIS / VHF and I'm running into some confusion over the NMEA 0183 wiring. My goal is to connect the Vesper to my older Raymarine C80 chart plotter so I can send GPS signal and AIS targets from the Vesper to the chart plotter. There's tons of information on baud rate and other settings, but the actual wiring is confusing. According to the Raymarine manual, it's NMEA interface has Input and output with -ve and + ve. The Vesper has NMEA TX and RX and A and B. It took me a long time to figure out A is + and B is - on the Vesper side. The Raymarine is fairly straight forward. I've read transmit from one device needs to go to reseive from another device and + goes to + / - goes to -. so I came up with the following wiring diagram (positions 3-6 are for the NMEA interface):



@bgary and @Marlin Prowell were discussing NMEA 0183 wiring over at the "New e-38 owner" thread (https://ericsonyachts.org/ie/threads/new-e38-owner-in-the-pnw.21018/) which got me thinking there's probably some good advice here. I haven't finished wiring it up yet. Does this look correct? If not, what am I missing?

 

[Marlin Prowell]

In NMEA 0183 networks, there are talkers and there are listeners. An example of a talker is a depth sounder or an anemometer. An example of a listener is a tiller pilot. A NMEA 0183 network, you typically connect one talker to one listener. Of course there are exceptions, but typically one talker connected to one listener. Each wire pair connecting a talker to a listener is a one-way conversation.

Some devices can be both, and in your case, both the C80 and the Cortex can be both talkers and listeners. In your diagram you have the C80 talker connected to the Cortex listener and vice versa. This is correct, but is it necessary?

These are two independent (one way) communication channels. You aren’t required to have both channels connected between your devices. In your use case, you want the Cortex to send AIS data to the C80 for display, so you should have the Cortex TX side connected to the C80 RX side. But, does the C80 have anything useful to tell the Cortex? I don’t think so. The C80 can transmit course correction information, but the Cortex doesn’t care about that. I think you can disconnect the C80 transmit/Cortex receive pair of wires. If you have a wheel pilot that understands NMEA 0183, then you might instead connect the C80 transmit pair to the wheel pilot.

There is one configuration setting you need to pay attention to. Typically NMEA 0183 networks transmit at 4800 baud, but this is too slow for the large volume of AIS data. NMEA 0183 has an alternate baud rate of 38,400 baud meant to handle AIS data. Your C80 can receive 38,400 data and the Cortex can transmit at 38,400 baud, but you must configure the NMEA connection in each device’s settings to do so.

As far as nomenclature, +ve means positive voltage, nothing more. With Raymarine notation, you need to read the additional text to discover the purpose of the NMEA wire. Standard NMEA 0183 notation is TX+ or TX A for one transmit wire and TX- or TX B for the other transmit wire. No additional explanatory text is necessary.

 

[Nick J]

That's great advice. I hadn't thought about that, but now you got the wheels turning. It looks like I may be able to bridge the TX (talker) pair from the Cortex and send the signal to the chart plotter, my old VHF, and the autopilot (for the wind steer function). I'm not sure how much I'd use it, but it would be fun to play around with. I'm using DIN rail blade disconnect terminals, so I can easily disconnect any devices that's giving me an issue. This is what I'm thinking of now:



I was reading the NMEA 0183 standard is based on RS-422 serial so it should be able to handle three listeners to 1 talker. The Cortex acts as a NMEA 2000 to NMEA 0183 bridge in both directions, so I would also be able to send course info from the chart plotter to the NMEA 2000 network.

 

[Marlin Prowell]

I like a good puzzle, and your network setup is a great one. I’ve been thinking about your revised wiring. Unfortunately, I don’t think it will work. You need to set the baud rate for the Cortex NMEA0183 TX lines to 38,400 to be able to transmit AIS information to the C80. The C80 can handle receiving 38,400 baud data, but I doubt that either the ICOM M504 or your autopilot can handle the high speed NMEA 0183 data. Most NMEA 0183 RX connections expect 4800 baud.

Perhaps instead you connect the auto pilot and M504 to the C80 TX output with the TX output set at 4800 baud. Everything that the C80 receives should also get repeated and sent out its TX output. But this raises other questions. Does the C80 try to send all the received AIS data out its TX lines at 4800 baud? If so, this would saturate the data output lines. Maybe it decides that if the C80 TX lines are set to 4800 baud, it doesn’t repeat AIS data. Maybe you can tell the C80 not to output any AIS data. So I looked at the C80 manual and down the rabbit hole I went.

The C80 manual lists the NMEA 0183 sentences it understands and also lists the sentences it transmits. The manual lists just three letter codes, so research is needed to figure out what each three letter code means. The C80 manual says you can turn off transmitting individual NMEA sentences, but again research is needed to know which ones to turn off to stop flooding the C80 TX output lines with AIS data.

Also in the C80 manual specifications section was the list of the the C80 connectors. Included in the list was SeaTalk2/NMEA2000. !?! Not many Raymarine devices have SeaTalk2 and I’ve always assumed that it was another proprietary SeaTalk protocol and cabling. Not so. Apparently it is NMEA2000 over a proprietary Raymarine cable. There is a Raymarine SeaTalk2 to SeaTalkNG cable, A06048, that you can use to make a NMEA 2000 adapter cable. Cut off the SeaTalkNG connector and attach a field installable male NMEA 2000 connector. Now you can connect your C80 directly to a standard NMEA 2000 network. The Cortex also has a NMEA 2000 connector, so the Cortex can send the AIS data to the C80 over the NMEA 2000 network and you don’t have the problem of NMEA 0183 baud rates and saturated data lines.

Maybe.

This eight year old post from Raymarine support says that the Raymarine E-series MFDs support NMEA2000 data on the SeaTalk2 connector except for AIS transceivers. Does that mean it cannot control the AIS transmitter, but can receive AIS data? I don’t know. It also says to update your device to the latest software, which is always a good idea. That post is eight years old, and perhaps things have changed. If you want to go this route, check with Raymarine support first and find out if your C-series MFD can receive AIS data over the SeaTalk2/NMEA2000 connector. Being able to move to a NMEA2000 network helps modernize your network and makes it easier to integrate other devices in the future.

Regardless of the path you choose, you should check with Raymarine support to find out if what you want to do is feasible.

Like I said, down the rabbit hole I went.

 

[Nick J]

Wow! That's extremely helpful. I was wondering about the baud rate, but I figured I would wire it up and play with the settings to see if I can get it to work. It's probably best to take a step back and list out my goals:

Current Equipment (off memory, so I could have missed, added or misrepresented something):

• Raymarine C80 chart plotter and radar - we only use this in fog where the radar is nice to have
• Raymarine ST40 (I think) depth (independently wired for redundancy and because I didn't want to glass in the hole after replacing the speed transducer with the B&G unit)
• Raymarine seatalk GPS (don't know the part number)
• B&G Triton display x 2
• B&G wireless wind
• B&G DST 810
• B&G ZG100 GPS antenna
• Vesper Cortex M1
• ICOM IM 504
• Raymarine seatlalk 1 to seatalkNG converter kit (not installed, see note below)

Long term:

• Replace the C80 chart plotter and radar with a modern unit - connect with NMEA 2000
• Replace Raymarine ST4000 wheel pilot with a below deck unit (this is a very long term goal)

Short Term

• remove the sea talk GPS unit on the rail and get GPS info from my B&G instruments or the Vesper Cortex
  • when I installed the B&G instruments, I tried to get the GPS signal from the B&G unit to the C80, but I couldn't get it to work, so I ended up just using it to power the Raymarine ST40 depth. I've removed it and direct connected the ST40 to a dedicated power circuit, but it's available to reinstall.
• Receive AIS from the CORTEX to the C80
• Provide GPS to the ICOM over NMEA 0183

Nice to have

• Wind date from NMEA 2000 to the auto pilot
• Course info from C80 to the auto pilot

I think I can accomplish everything on the list if I can get the NMEA 2000 to Seatalk NG cable and settings to work. That would allow me to set the baud rate from the Cortex to something the Auto Pilot and VHF can tolerate. Looks like I have some reading to do. too bad I just ordered a replacement Raymarine NMEA 0183 cable (those things are crazy expensive for what they are. Thank You!! I'll keep you updated on what I end up with.

 

[Marlin Prowell]

In this post, You have your ST4000+ connected via the Seatalk connector to the NMEA 2000 bus. You cannot do that.

Raymarine has four(!) versions of Seatalk, all different.

• Seatalk or Seatalk1, a three wire oblong connector
• Seatalk2, a five wire chunky connector
• SeatalkNG, a six wire M16-like connector
• SeatalkHS, a RJ45-like connector

Seatalk1 is a Raymarine proprietary network, incompatible with everything else. You need a gateway to connect your ST4000+ to the rest of your devices. Networks that are incompatible can be incompatible in their electrical connections, and also be incompatible in the data sentences they speak. A gateway will have connectors for the networks being bridged, but a gateway also knows how to translate between the two different data languages that the devices speak.

Here are two ideas.

Connect the C80 to the NMEA 2000 network as I mentioned above. Connect the ST4000+ Seatalk1 connector to the C80 Seatalk1 connector. The C80 likely acts as a gateway between Seatalk2 (NMEA2000) and Seatalk1, so any data sentences the C80 sees on the Seatalk2 connection will get translated and sent to the ST4000+ via the Seatalk1 cable.

The ST4000 is a Seatalk1 only device. The ST4000+ has connections for both Seatalk1 and NMEA 0183. Connect the C80 to the NMEA 2000 network as I mentioned above. This will let the C80 see all the good data on the NMEA 2000 bus. Connect the ST4000+ NMEA 0183 RX A and RX B to the NMEA 0183 TX A and TX B connections on the Vesper Cortex. I expect that the Cortex is a gateway between NMEA 0183 and NMEA 2000, though I have not verified it. This will let the ST4000+ see routing data from the C80 via the NMEA 2000 bus and translated by the Cortex.

 

[Nick J]

Raymarine makes a Seatalk 1 to SeatalkNG (NMEA 2000) converter:

SeaTalk NG and NMEA 2000 | Product | Raymarine

Cables and accessories for Raymarine chartplotters, autopilots, and instruments

www.raymarine.com

SeatlakNG is Raymarine's version of NMEA 2000. It uses the same CAN Bus protocol as NMEA 2000, but uses Raymarine proprietary connectors instead of M12 connectors. A slight oddity with SeatalkNG is their backbone cables are 6 wires instead of the standard 5 wire NMEA 2000 cables. The 6th wire is a yellow Seatalk 1 wire, but I can't see where it's used. I can verify the converter is working as advertised and it's passing wind data from my NMEA 2000 network to the ST4000+ autopilot. I did have to cut the red power connection between the converter and autopilot to stop the autopilot from back feeding my NMEA 2000 Network.

Before I remembered I had the converter from a previous failed attempt to bridge my old Raymarine stuff with the new B&G NMEA network, I was planning to connect the C80 Seatalk 2 port, but Raymarine has a lot of good post about the limited NMEA 2000 messages supported by he C80. The original intent of the Seatalk port was to gather engine data. GPS, AIS, and other instrumentation messages were never implemented on the C80. between the cost of Raymarine proprietary cables and the Raymarine blog posts, I don't think its worth testing myself.

I'm back to connecting the C80 to the Vesper Cortex through the NMEA 0183 port, but I'm still waiting for the cable to arrive. The only issue with this method is it limits what other NMEA 0183 devices I can connect to the Cortex because of the baud rate issue you mentioned above. I did read a post somewhere else detailing how to set the baud rate on the ICOM m504, but I wasn't able to find the setting on my unit.

 

[Marlin Prowell]

I did not catch that the Raymarine backbone device in your diagram that connects the ST4000+ to the NMEA 2000 bus was actually a gateway. It looks just like a regular SeatalkNG backbone but with an odd yellow connector. I thought it was only a backbone, but it is actually a gateway that translates Seatalk1 data to NMEA 2000 data and vice versa.

I’ll just say that trying to solve all this is a bit of an intractable problem. The C80 is the Gordian Knot at the center of it all. Replace it with a NMEA 2000 compatible chart plotter that also has NMEA 0183 connections and all these interconnection problems disappear.

 

[Nick J]

Totally agree. The c80 has run its cource. We only use ours for radar on foggy days. My main driver for connecting it to the rest of the network is eliminating the old GPS antenna by using the Cortex GPS. Everything else is just an interesting experiment until it's replaced with a modern unit. We use phones tablets and computers for navigation and those just got exponentially better with the addition of AIS and instrument data over the Cortex wifi connection.