A brief history of marine instrument networks
by Mark Jardine 25 Jun 13:30 UTC
Spirit Yacht 52' Oui Fling combining A+T BFD big colour display with an N2K processor © A+T Instruments
Interconnected electronic systems on yachts have been around since the 1980s and have become standard on yachts of all sizes. There are various ways to network sensors and devices, and to understand the advantages and disadvantages of each, it is useful to know the history of how the sector evolved.
One man who has been involved since the outset, and continues to develop at the cutting edge, is Hugh Agnew, the Cambridge-educated mathematician who is one of the founders of A+T Instruments in Lymington, so I spoke to him to find out more...
"Historically, for high end boats using B&G equipment used a serial bus called Fastnet, which has been with us from the late 80s until 2013, and is still a very widely used system because of the enormous number of legacy boats using it. It's very robust, well designed in the first place.
"Since the year 2000 the NMEA, the central organization for electronics, introduced NMEA 2000 or N2K which is very similar, in that it's a serial bus running faster. It's an industrial bus called CAN bus, with an overlay protocol dictated by NMEA. The problem is it tries to be all things to all men but has ended up with lots of crossover and compromises.
"The problem was that the protocol that the NMEA devised never thought of, and never could think of, all the devices that we put on systems like lower deflector percentage, daggerboard cant, and the myriad of other devices which are now on yachts. So, manufacturers invented private messages on N2K, which are proprietary to them, and other manufacturers had to puzzle out what these were.
"For example, in the load area, Diverse and Cyclops and everybody else copy and use each other's private sentences to try and send load data around, which becomes a mess logistically.
"N2K systems are vulnerable as any water in the cable, or any defective device on any part of a N2K cable, brings the whole lot down. Because they can, people connect N2K systems to everything: the underwater lighting, the black tanks, turning the audio on and off. So you could be trying to sail your boat across the Atlantic at night in the pitch black, true wind angle is the only thing standing between you and a standing gybe on a superyacht, and the audio system could crash it.
"So, N2K is quite a vulnerable system, has all sorts of length limitations, and the guide to fit it is enormously difficult. It was never intended for the purposes it is used for now.
"When we started A+T, Richard and I took the view that the long-term solution for the backbone, the network of a boat, should be Ethernet. It's incredibly fast, no problem with bandwidth, and just a single cable around the boat links everything together: the sensors, the displays, the processors.
"The processors can be distributed, which is what we do, so that the core brain is possibly located at a nav table, but at the base of the mast, there will be little interface boxes that deal with just the wind or depth.
"Being used throughout the IT Industry, there is an array of third-party equipment, free availability of cables, and you can use fibre-optic if you want to and you have virtually unlimited bandwidth.
"The most important thing about Ethernet is that if you cut the cable anywhere, all that happens is the data downstream of that cable goes - it doesn't affect anything else. Just as if a device on that system fails, it doesn't pull anything else down with it - just that device stops working. It's much more robust."
Ethernet was commercially introduced in 1980, first standardised in 1983, and refined to support higher bit rates over the years (the latest is 400 Gbit/s, which compares to the 250 kbit/s of N2K - over a millionfold order of magnitude greater).
Being a system which isn't marine in origin, but is used industrially, it is used throughout the internet. Therefore, all of the protocols have been worked out years before you implemented it in a marine environment.
There are a plethora of ways to monitor what is happening on Ethernet which means diagnosing issues becomes far easier, as Hugh explains:
"There's all sorts of software programs, such as Wireshark, to monitor what's going on. There are also hardware devices to check Ethernet connections.
"N2K, a serial device developed by a committee, is full of dark arts and unknowns. Ethernet is a completely open system, and everybody understands how to troubleshoot it, how to make it work."
As Hugh described earlier, Fastnet and N2K are commonly in use on existing yachts, so how do you make these compatible with Ethernet as a yacht transitions between systems?
"The A+T Sailing Processor is effectively completely multilingual, so our core brain uses Ethernet as the backbone, but it also speaks N2K, so it's got a port for that.
"It also speaks Fastnet, so that we can support boats that have got old systems on and indeed, we've got quite a few boats that are hybrid. I've got some old displays running on Fastnet, and then new displays, particularly big colour displays, are running on Ethernet. It's no problem at all, and it's also got interfaces for NMEA 0183."
So, switching to an A+T Sailing Processor, you can effectively integrate all of your legacy sensors, but get rid of a lot of the reliability issues you may have had, allowing you to gradually switch over sensors and displays over time.
"That's exactly right, and we're increasingly finding boats that fitted first generation N2K systems who are now absolutely fed up with the reliability issues and putting an A+T system with an Ethernet backbone in, but they can still run the plotters and sensors that they've got on board which were either analogue, NMEA 0183, or N2K."
For engineers, who may be called to a yacht on a regular basis with electronic reliability problems, where the yacht may not be in for a refit for 18-months or more, switching processors could solve problems in both the short and long term, thanks to A+T Instruments' technical knowhow.
"The reliability and support of the A+T systems is so good that the concept of having to change the whole thing slightly goes away. If you can put a hybrid system in, and if it's working, just leave it that way until such time as those other devices become end of life. A lot of our work is coming from that, but remember that it's not just the equipment, it's the support that counts. Once you've bought into an A+T processor, we will, by hook or by crook, sort out how it works with the rest of your system."
Ethernet provides huge advantages when it comes to remote diagnostics as Hugh explains:
"The biggest single tool is TeamViewer. I've been on two TeamViewer sessions this morning so we can, to all extent and purposes, be as if we were on the boat anywhere in the world. All we need is a captain or engineer standing there with a WhatsApp, which is easy now with Starlink. We can extend to helping them through the menus on a Zeus plotter or a Raymarine plotter to find the source of data that's coming from the processor. We can support non-A+T equipment, providing it's in an A+T equipped boat.
With the A+T team's depth of knowledge of instruments, esoteric issues can be identified and diagnosed in what is a hugely complex field:
"It's a whole spectrum. You learn about things that happen often, but there can be ones that are a bit harder than we thought. There's a whole gamut of things that we look at, but when we analysed a few years of support calls, only a very small proportion were actually about defective equipment. It's nearly always about compatibility, configuration or troubleshooting various pieces of equipment that are connected to one another. We have five people here that have twenty to thirty years of knowledge, each of different equipment.
This led me to the question of whether there was any substitute in a technology company for engineers who know their stuff. To which Hugh answered in a typically amusing style:
"It was always thought that if you put enough monkeys in front of enough typewriters that they would eventually type the entire works of Shakespeare. The internet has proved that this is not the case. It is inconceivable that these systems in our lifetimes, and probably our children's lifetimes, could ever be so automated that they never would need any understanding."
A+T make many highly accurate sensors themselves, such as their extraordinary 500 series Wind Sensors, but are also pragmatic about other manufacturers' sensors and instruments on the market, in specialised areas, which they must then work with.
"It's a really interesting question, and in fact, we are working on two new builds at the moment where we are advising on a lot of equipment that is outside of our own supply, because we just got such a depth of experience on race boats and super yachts.
"For instance, at the low end for a conventional magnetic compass, at the moment we're recommending a Lars Thrane LT-500, as they make an excellent, small magnetic compass, so we nearly always specify that.
"GPS compasses, that is a compass that derives its heading from the GPS constellation, are getting relatively less expensive now, and that gives you an absolute, true heading. It's not very safe on its own, as if the GPS went down you'd have no heading, so you probably would want a magnetic compass as well, but for race yacht instruments it's a big step forward on a magnetic compass, and it doesn't have the deviation or variation issues.
"We're also seeing a lot of boats now putting a fibre optic gyrocompass on, because the price of those has dropped, thanks to companies like iXblue, and a new Australian company called Boreas. At least ten A+T boats are now running fibre optic, True North seeking gyro compasses.
"In the wind sensor area, as you know, we are really frustrated with the one options on the market, so we've built our own range of wind sensors, which are faster response, more accurate and more robust than anything else on the market and more robust."
"We're doing a lot more in the load cell area, because loads are now being measured on lots of boats, and there's a myriad of companies now, all with different angles on the offerings there. Cyclops has emerged over the last few years, concentrating primarily in the small boat area and wireless, but starting to step up into the big boat area. They're doing the wired load cells on the new Royal Huisman-built Aquarius. Then you've got Diverse, who have probably owned the marine load cell space for a long time, and then in the last year or two, we've seen Southern Spars entering the space with a system called Synapse, which is really oriented towards measuring the loads in rigging."
I asked off-hand whether A+T had even met a sensor they couldn't integrate with and got a very definite answer:
"No, and here's the reason why. Our highest end processor is called the ATP X, which takes all the proven hardware of the A+T Sailing Processor and adds a layer of user-programmable Node-RED software on top of it, which can read anything from any interface port and device. It doesn't matter if it's binary or ASCII, we can bit bash it, turn it into useful data, calibrate it, and export it into the processor's calculations. We can write custom code to do absolutely anything."