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Thread: Adding Garmin (NMEA 2000) devices to a Raymarine (SeatalkNG) network

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    Contributing Partner Teranodon's Avatar
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    Adding Garmin (NMEA 2000) devices to a Raymarine (SeatalkNG) network

    When I installed a Raymarine EV-100 wheel autopilot, I had to set up a simple SeatalkNG data network to link all of the pieces together. Later, I acquired a Garmin EchoMap 54CV CHIRP chart plotter. I ran it in stand-alone mode on top of the pedestal, i.e., with nothing more than a 12V power connection. Finally, I got a Garmin 210 VHF radio. The radio picks up AIS signals, and can display the targets on the Echomap, but the two devices have to be connected via a Garmin NMEA 2000 network. I was going to put together the basic pieces for that, but then I thought: isn’t it kind of dumb to have two networks on one boat? So I did a bit of research and discovered that it would indeed be dumb. As it turns out, the “proprietary” data networks from companies such as Simrad, Raymarine and Garmin, are essentially identical and, in theory, interoperable. But they use different connectors. By doing some splicing and soldering, I was able to hang my two Garmin units on the existing SeatalkNG system, as follows.

    (Before going on, I apologize to the many Forum members who already know all this. In fact, it’s not such a big secret).

    The basic network architecture is simple. A single backbone runs through the boat. It consists of segments of cable that are joined by T-connectors. Each T-connector links to a device (sensor, chart potter, display, radio, etc.) with a “drop cable”. The backbone (and the drop cables) have four wires: signal high, signal low, +12V power, and power ground. At one place, 12V DC power has to be supplied to the backbone (again, using a T-connector). On each end of the backbone, one has to insert a termination resistor. That’s it. The only way in which the components from different manufacturers differ is in the connectors (sex, pin layout) that go on the T’s, the backbone and drop cables, and the terminators. There are special T’s that support several drop cables. Here is my new system:

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    The network includes 12V power, but only certain low-power devices can use it (for example, the display for the autopilot). The autopilot drive, the radio and the chart plotter all need separate power connections, each with a circuit breaker. Makes sense.

    Looking at the cables that came with my Raymarine units (autopilot, speed, depth, wind) and Garmin units (chart plotter, radio) I concluded that I needed to create “hybrid” drop cables with a female Garmin connector on one end, and a Raymarine female connector on the other. Regular Garmin drop cables are male/female. (NB. despite the best intentions, all connectors in this posting are cis-gendered).

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    I had to buy a couple of NMEA 2000 drop cables, and a SeatalkNG T-connector. In the end, I didn’t save much money by combining the two systems.

    I struggled for a couple of hours with the hybrid cable that just wouldn’t go down the ridiculous 1-inch Edson pedestal guard (I had to do the splicing in the quarterberth, underneath the pedestal). I put it all together and powered up with some trepidation. No worries! Now I have AIS targets all over the place, and alarms going off for a potential collision with every barge and ferry that approaches my marina.


    The manufacturers like to pretend that their proprietary networks are unique, and they want you to buy their hardware. I talked to the (normally helpful) Garmin technical assistance people, and they got very snippy when I asked about integrating their devices onto the Raymarine network. In general, there seems to be a lot of hype in this domain. Thus, company literature likes to grandiosely refer to the backbones as “transmission lines”. In reality, I suspect that they are far less than that. The rise times are too long, the propagation distances too short and, anyway, a pair of humble copper wires hardly qualifies. The vaunted termination resistors on each end of the backbone are probably there simply because that is what the drive circuits expect to see in, essentially, mundane DC operation.

    So the bottom line is that (except for some exotic devices) slicing and dicing of cables should work for any brand of NMEA 2000 compatible network. You can even buy the hybrid cables, but they come in fixed lengths which isn’t always what is needed.

    Last edited by Teranodon; 06-11-2018 at 11:33 PM.
    Stefan Michalowski
    Friday Harbor, WA
    1988 Ericson 34 "Talpa"

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    Quote Originally Posted by Teranodon View Post

    The manufacturers like to pretend that their proprietary networks are unique, and they want you to buy their hardware. I talked to the (normally helpful) Garmin technical assistance people, and they got very snippy when I asked about integrating their devices onto the Raymarine network. In general, there seems to be a lot of hype in this domain. Thus, company literature likes to grandiosely refer to the backbones as “transmission lines”. In reality, I suspect that they are far less than that. The rise times are too long, the propagation distances too short and, anyway, a pair of humble copper wires hardly qualifies. The vaunted termination resistors on each end of the backbone are probably there simply because that is what the drive circuits expect to see in, essentially, mundane DC operation.

    So the bottom line is that (except for some exotic devices) slicing and dicing of cables should work for any brand of NMEA 2000 compatible network. You can even buy the hybrid cables, but they come in fixed lengths which isn’t always what is needed.

    I had to do a lot of research when I purchased my new to me 1994 E380 due to it having older Raymarine chart plotter, instruments and I was adding the new EV-100 autopilot. In fact, depending on age, Raymarine can be proprietary. NMEA has gone through changes over the years. If you are working with NMEA 2000 then all should be good, as devices can talk and listen on the same bus and should all be talking at the same baud rate, sending out standard NMEA sentences. All you need to do is get your wires spliced correctly and you can make adapter cables, which I did on my previous boat. Termination resistors are important as to not have reflections I suspect.

    But if you are dealing with older Raymarine, with their original Seatalk (which can be like three different flavors of SeaTalk), then you can run into problems and it isn't just doing splicing. The very early Seatalk was a proprietary group of sentences on the bus, and the bit pattern was not standard, so the messages look like garbage to other devices. And the wiring was different. I found a website I think in Denmark that deals with all this and it was very helpful. People on the site built their own multiplexers to tie the old and new NMEA together.

    When you have NMEA 0183, then you are dealing with one way communications. You have a single talker and multiple listeners. You have to get all that worked out. And make sure the baud rate is correct. Like with VHF radios, they are listening for NMEA messages and expect NMEA 0183 at 4800 baud, where as most other devices are using 38400 baud. Then you need a multiplexer to join your VHF radio to your NMEA 0183 talker, which would be sending out say the GPS sentences that the VHF radio wants to see so it can send your coordinates when you press the DSC button. The multiplexers usually have multiple input and output ports that are configurable to different baud rates.

    And getting back to the older Raymarine NMEA, Raymarine sells a multiplexer that can tie the older Seatalk to the new Seatalk, so older instruments can output their NMEA sentences to the NMEA 2000 bus. Say the old ST50 wind instrument could put its data out onto the backbone.

    On my last boat, a CAL 33-2, I installed the Garmin Steady Cast heading sensor, Garmin Radar, Garmin 740s chart plotter and the EV-100 autopilot. This was all tied together on one NMEA 2000 backbone. Well, the radar tied directly to the 740s. But all the other gear was connected to the NMEA backbone. I fabricated a couple of adapter cables and bought one. As you said, very doable by the DIY as long as you have the pin outs and wire colors. I found a Lowrance NMEA starter kit on Amazon for a good price that contains a long backbone cable, some spur cables, power cable, T's and terminators. All for like $60. I took the backbone cable and spliced it to the backbone cable that came with the EV-100. Made a nice long backbone that then had T's of the generic type and they Raymarine type. I could then spur off to Garmin or Raymarine equipment, just making sure to come off the correct T. Saved some money using the Lowrance cables as to buy Raymarine or Garmin cables is quite expensive. Note that the Lowrance cables are compatible with Garmin. Not with Raymarine. But if you are only dealing with the EV-100, the cables included with the kit get the job done.

    Raymarine cables are unique in that the cable lock is at the T, not on the cable end. Raymarine touts this as a plus as the end of their cables is very small and will fit through a smaller hole. But, it also means that you must buy Raymarine connectors and cannot use any generic part which is usually much cheaper.
    Last edited by Leslie Newman; 06-13-2018 at 07:04 AM.
    Leslie Newman
    E-380 "Osprey"

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    Contributing Partner Slick470's Avatar
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    All of my instruments are B&G on a NMEA 2000 bus but I added a Raymarine Evo autopilot. I ended up using a Raymarine adapter cable on the end of my NMEA 2000 bus to tie in the autopilot. My installation was relatively simple since I didn't have to deal with the pedestal.

    From what I've found the big differences with the different manufacturers is what custom sentences that their devices input/output. For instance, my B&G chart plotter can control a B&G AP, but it won't control the Raymarine AP. I can see the devices on the network from each side of the system, and they can share and display data, but not control sentences.
    Andy H.
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    Controlling Ev-100 from Garmin

    I assumed my Garmin 741xs would be able to control the Raymarine EV-100, didnít buy the NMEA to Seatalkng cable yet. Does anyone know if it will work or not?
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    Contributing Partner Slick470's Avatar
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    Generally I think the answer is no, but you may luck out. I think that the problem is that the input/output sentences that each manufacturer uses to control the AP aren't standard NMEA 2000 sentences so one manufacturer's device might not recognize a command given though another device and ignore it as noise.

    This seems to be the case between my B&G Vulcan and my Raymarine Evo AP and was confirmed by another owner with the same setup with both manufacturers.

    I think the response they got was something like "why would you want to do that?" or "You should just buy one of our AP's/MFD/instruments". I would have been happy with a B&G AP, but they are much more expensive than the Ray Evo and they didn't have an above deck tiller option, which would add even more cost to go with a below deck ram.
    Andy H.
    1990 Ericson Olson 911S #149 Hawkeye
    Deale, Maryland
    Yanmar 2GM20F

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    Contributing Partner Teranodon's Avatar
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    Quote Originally Posted by Slick470 View Post
    Generally I think the answer is no, but you may luck out.
    This is my guess also. The variety of Garmin devices is bewildering, and compatibility is even more complex, even in their own product line. For example, I am vaguely thinking about getting a Garmin radar (the Minister of Finance is far from convinced that we need one). You would not believe the vast list of Garmin displays that do not support this or that radar model. Thus, your 741xs won't work with the Fantom model, but the 742 will. Even worse, I discovered that the Garmin VHF 210 will talk to the Echomap 54cv CHIRP, but not to the plain Echomap 54cv. And so on. It's maddening. Garmin should be able to do better.
    Stefan Michalowski
    Friday Harbor, WA
    1988 Ericson 34 "Talpa"

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    Cool Garmin + Evolution

    Quote Originally Posted by GrandpaSteve View Post
    I assumed my Garmin 741xs would be able to control the Raymarine EV-100, didnít buy the NMEA to Seatalkng cable yet. Does anyone know if it will work or not?
    I have a Garmin 7408 and a EV-100 Tiller on my Macgregor 26s. I built the cables using an NMEA end and cutting a seatalkng cable and wiring it to the end.

    The 7408 can deliver route information to the ev100, but it cannot control (engage auto or standby) the ev100. This may have changed in an update over the last year but I doubt it.

    Even with route information, once you have engaged track from the p70 you have to "OK" each waypoint change at the p70 before it will steer to the new track.

    Hope it helps!

    Sean

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    Moderator Christian Williams's Avatar
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    >>>>I apologize to the many Forum members who already know all this. In fact, itís not such a big secret

    Maybe not, but it is very useful to hear confirmed that cutting and splicing these proprietary cables can be done.

    It was with trepidation I first sliced off the end of a Garmin cable to make it fit through the binnacle guard tube. My splice was none too pretty, using household aluminum foil to imitate the original insulation. But it works fine, and on my depthfinder cable, too.

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    Quote Originally Posted by GrandpaSteve View Post
    I assumed my Garmin 741xs would be able to control the Raymarine EV-100, didnít buy the NMEA to Seatalkng cable yet. Does anyone know if it will work or not?
    My 740s on my CAL could not command my EV-100. All were tied together, and I suspect that the radar worked better having the heading sensor, but the EV-100 was not really recognized by my chart plotter as I remember.
    The EV-100 would steer dead nuts on though.
    Leslie Newman
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    Senior Moderator Loren Beach's Avatar
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    Electircal Several Bus Lines

    I upgraded the whole radar "system" a few years ago to a Lowrance 9" plotter and linked hi-def radar. The heading sensor was required to sync the chart and radar images on screen. This also allows the little boat icon to always point forward, even at rest.

    It's a good system IMHO, and one vary basic reason is that the plotter has a friction chip door and does NOT disturb our steering compass, just beneath it on the ss binnacle guard.

    This all uses a small-diameter cable "backbone" with several screw-in taps into it, mounted inside a cockpit lazaretto.

    I guess I am ok being associated with Ned Ludd (altho I do not attend the meetings and have not yet personally attacked a knitting mill).

    Our Raymarine wheel pilot is separate and also our still-working-fine Raymarine ST-60 instruments are all on their own separate antique bus as well.

    FWIW, and YMMV, we used to have a Garmin plotter. Poor software and poor firmware. While I have used and depended on their hand held GPS units for years, I consider their fixed-mount stuff to be too buggy to allow aboard. They also use only powerful permanent magnets for their chart chip doors, and have be kept 20 to 36 inches away from the compass. OK for power boats with wide dash boards, perhaps.
    Last edited by Loren Beach; 06-14-2018 at 06:54 AM.
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