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ContinuousWave: Small Boat Electrical
NMEA-0183: Standard Connector
|Author||Topic: NMEA-0183: Standard Connector|
posted 12-23-2011 08:35 AM ET (US)
The NMEA 0183 connector discussions have been very useful. As a result of reading them and based upon my personal klutzy method of simply making these connections via a terminal strip I've reached a conclusion.
Those VHF radio manufacturers who have opted not to have an NMEA 2000 compliant product should at least provide a standard connector for the 0183 conductors provided for data exchange with a chart plotter or GPS map. If the plotter manufacturers would provide a standard receptacle this business would be so simple even I could do it.
Thanks for the opportunity to whine.
posted 12-23-2011 09:47 AM ET (US)
The manufacturers and NMEA have not been cooperating very well together on connectors. If you notice, just about every electronic device on a boat has a different power connector, yet they all run from 12-VDC. Why not adopt a standard power connector?
In NMEA-2000 the NMEA standard proposed a connector, but the manufacturers ignored it in the initial products they produced, then they adopted it--for a while--then they moved away from it. There is a standard connector specification for NMEA-2000 but we still have manufacturers not adhering to the standard.
In NMEA-0183 there never was a standard for the connector. Some devices don't have connectors at all; they just furnish bare wires in a cable.
Even wire insulation color is not standardized. Most other boat wiring follows a recommended practice (from the ABYC) for wire insulation color. NMEA-0183 wiring is all over the color chart for using color-coded insulation. There is no standard at all.
NMEA and the manufacturers even failed to agree on the names of signals. There is no consistency in naming of the signals across various manufacturers. Some call it TX, others "Talkers", others "sender" and still other "transmitter." And then there's "listeners", "receivers", RX, and so on.
And NMEA could not get manufacturers to even use the same type of electronics. Some use differential inputs and outputs, some use single-ended, and some use a combination.
It is no wonder that the average boater--who is not an electronic technician nor a serial data communication expert--can't connect devices using NMEA-0183 very easily or successfully.
A standard connector, with a standard pin-out, with standard wire colors, with standard signal names--they all would make interfacing devices much easier. That's my rant.
posted 12-23-2011 09:14 PM ET (US)
NMEA has also been less than user-friendly at the standard process. They operate on a model that comes from the 1950's--not a modern model. NMEA creates standards and they would like to sell them for about $2,500 a copy, mainly to a few industry members--big electronics firms making marine electronics.
Even if I bought a copy for myself I could not disclose the information contained in them to my readers. This is the sort of secret-society model of doing business that used to work in the 1950's--it does not work very well in 2012.
I understand that NMEA wants to generate income to sustain itself. They have a few people on their staff who would like to make their living being the employees of NMEA, and the organization needs to generate some income to sustain itself. However, as we have seen in the modern world with the internet and truly open standards, progress toward global cooperation and interoperation is not aided when it costs individuals $2,500 to find out what the standard is supposed to say, and then to pledge to keep it a secret once they join the society. NMEA would be much farther ahead--and so would marine electronics--if they sold their standards for $5 a copy to a million people instead of the 100 companies that pay the $2,500 fee.
NMEA has not done a very good job with providing marine electronics with a standard. We are still working on the NMEA-2000 protocol getting a foothold in marine electronics, and it is already almost 2012. Using open standards the HTML protocol has come to totally dominate global communications in far less time. Imagine what marine electronics might be like if NMEA did not try to act as the guardian of information and sell it at $2,500 per copy!
Imagine if the personal computer worked like NMEA. You'd buy a mouse and then you'd have to figure out how to wire it to your computer, using various wire colors, no standard connectors, and every wire would be called a different name by each mouse maker. If you wanted to get the details of the interface you'd have to buy them at a cost of $2,500. That's today's marine electronics using the NMEA standard.
posted 12-24-2011 07:19 PM ET (US)
I have to wonder if an additional reason companies do not adopt the recommendations is that they like the idea of advertising they can connect via a standard, but frown on the idea that you can connect to a competitor’s equipment. After all, if you commit to company x's GPS, I am sure they would like to encourage you to purchase their sounder or autopilot and not company y's sounder/pilot.
It certainly can influence the decision making process in purchasing follow-up equipment. Few people possess the technical background to make indirectly compatible devices talk to each other. Although I suspect I could (though I have not) I would be hesitant to try because if I could not get them to talk to each other, it is unlikely a dealer is going to accept a modified used electronic device under their return policies? Most places won't accept an electronic device for return once it is opened, let alone modified.
posted 12-25-2011 03:11 PM ET (US)
The fallacy there is that it's just about as hard to connect
two devices from the same manufacturer.
Given that the USCG is concerned about the number of DSC
posted 12-26-2011 03:19 PM ET (US)
Even if a boater over comes the obstacles put in his way by NMEA and the lack of clear standards for interconnecting devices, and the boater manages to make proper electrical connection between devices, we still have more problems to be solved. We now have the devices talking to each other, but what should they say?
In the case of a GPS receiver there can't be all that much data it can offer. There is the position, the time, and perhaps the velocity. In current NMEA standards there are several possible sentences which can be sent. It seems hard to believe that in the modern world that a GPS receiver couldn't send almost all the data mentioned above in one sentence.
I have interconnected devices and found that listener A wants to hear a particular NMEA sentence from the GPS receiver, while listener B wants another. It shouldn't be this complicated. Having six different sentences just provides more chances for things to not work well together.
Here is a bit of a rant about what's wrong with NMEA sentences related to GPS
along with a suggestion of a remedy.
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