Originally Posted by Sir Rondo Normal
the question is, which is the better way to go, convert the older 0183 gear to n2k or convert the n2k gear to 0183?
From a highly technical standpoint....if it ain't broke don't fix it.
NMEA-0183 is a point to point serial
line protocol. Connecting many devices to many other devices is a hassle requiring a multiplexer: expensive if you'e buying
one. Frequently you can get away with connecting many devices to one central chart plotter but these tend to come with fewer NMEA-0183 interfaces on than they once did: Modern Raymarine
plotters have far fewer NMEA-0183 options than my 4 years old C90W for example.
NMEA-2000 is a better idea, bus oriented and many-to-many but it's still 80s technology and you still need ethernet to run radar
and sonar images
around the boat. You've already made the investment in a backbone. Connecting new stuff to that rather than running 4 NMEA-0183 wires makes sense.
The apparent resurgence of NMEA-0183 in software
applications is down to the licensing model the NMEA uses for their protocols. Unlike Internet
protocols which are published and "open" to encourage interoperability and innovation, the NMEA is an operation from a different industry and time which requires users of its protocols to license
them at a cost and doesn't allow them to be used in open source software
The contents of NMEA-0183 was determined by various methods including reverse engineering and widely published due in a large part to the efforts of open source advocate Eric Raymond. Although I don't understand the complexities of US litigation culture, my understanding is that the fact that it is "out there" makes pursuing people for "stealing" it tricky. NMEA-2000 on the other hand is still "closed" (although you'll find various projects which have partially decoded it), costs thousands of dollars to license
, and a can controller is slightly less simple to add to a computer than a serial
connection. Consequently when software, particularly open source software, uses the upper layers of an NMEA protocol over Internet
Protocol (over wifi
or ethernet) they chose NMEA-0183.
The question is what's coming next. We were supposed to be seeing NMEA OneNet (the new ethernet-based protocol) by now but it hasn't materialised and has all gone very quiet. Word on the street is that marine electronics
companies can't get their heads round IPv6 but that's just gossip. SignalK is being touted as the open source alternative for web applications but in its current
form it's hugely inefficient and inappropriate for an NMEA-replacement in embedded devices. The focus seems to be on using NMEA protocols from device to a server, building the SignalK data model on said server and using SignalK to feed end-user applications. Consequently it doesn't solve your "what do I connect my devices with?" problem.
Once again: If it ain't broke, don't fix it. You have an N2K backbone. You have a converter. It will probably be easiest to connect new stuff to N2K if the device you want at the price
point you can afford has an N2K interface. Personally I still have 25 year old seatalk
instruments. They work. When I can replace it all with a single
piece of UTP I'll think about it.