*THE HULL TRUTH is the world's largest FREE network for the discussion of Boating & Fishing. Whether you're researching a new boat, or are a seasoned Captain, you'll find The Hull Truth Boating & Fishing Message Forum contains a wealth of information from Boaters and Sportfishermen around the world.
Welcome to the updated THT!
If you are having trouble signing in, please email feedback@thehulltruth.com with your username and we will help you. We thank you for your patience as we help you access the new site!
Random Quote: "You can't know anything about anything, without knowing at least something about everything."
NMEA 0183 is the spec for the most popular communication protocol for marine electronics for the past few years. NMEA 2000 is a newer spec that has more capabilities.
I know that a NMEA 0183 device cannot interpret NMEA 2000 data, I'm not sure if NMEA 0183 data can be interpreted by an NMEA 2000 device.
As far as I can tell, you cannot wire a NMEA-0183 serial port directly to an NMEA-2000 bus. There are several reasons for this:
--NMEA-2000 is a bi-directional data bus; NMEA-0183 is not bi-directional. A NEMA-0183 device has separate send and receive interfaces.
--the electrical signal levels are probably not compatible
--the protocols of the data transmission are probably not compatible
I have to say "probably not compatible" because I do not have the full information about either standard. Although NMEA likes to promote these as open standards, obtaining information about them is very expensive. I have not invested the several thousands of dollars needed to purchase the information.
Some companies are advertising protocol convertors which will bridge between NMEA-2000 buses and NMEA-0183 devices. Unfortunately, using such a convertor bridge will probably not be attractive due to the cost and complexity of configuration.
LOWRANCE is a leading manufacturer of devices which support the NMEA-2000 protocol, so it should not be difficult to select one of their products which is designed to operate on a NEMA-2000 network.
Each requires it's own wiring. You can't plug a device using one into another. Many chartplotters will support both. But at the sensor end, and along the cabling back to the display, you can't plug one into the other's setup.
What's in your boat now and what are you interested in adding/changing?
__________________ -Bill Kearney, 34' Four Winns 348 Vista
jhebert - 4/26/2006 11:45 PM
Yes. Just like your telephone. Bell engineers worked out how to do this back in the 1870's.
Which, technically, is does not use a single wire. Nor do NMEA-0183 or NMEA-2000. They both use a transmit and receive line. How they use it and what's on those lines is different between the two standards. Needs have grown and the specs have grown to attempt to accomodate them. Regular -0183 works fine for most simple data needs. But when you start getting into live engine data and other higher-speed sources, along with devices that want to interact bi-directionally, using -2000 is a better solution.
Nothing uses a single wire; it is just sometimes the second wire is the chassis or the earth. You always need two wires in a electrical circuit.
Actually my analogy to the telephone line is an astoundingly accurate one. The Bell Telephone system operates with a 2-wire balanced transmission line that operates at about 600-ohm impedance. The NMEA-2000 data bus uses a 2-wire balanced transmission line at 200-ohm impedance. There is no separation of transmit and receive data. All senders and all receivers connect to the transmission line and transmit or listen as appropriate. This is exactly how your telephone system works, too.
The Bell System carries the power (-48 V) on the transmission line, but NMEA-2000 uses a separate pair of wires to carry the power. That is why there are two pairs (four wires) in a NMEA-2000 bus. One pair for data; one pair for power.
Of course, NMEA-2000 uses digital signaling. The receivers listen with a high impedance; the transmitters just swing the voltage on the bus up and down as needed to transmit their data. But the whole process occurs on the same bus.
In complete contrast, NMEA-0183 uses entirely separate receive and transmit lines to exchange data. Each device has a separate transmit output circuit and a separate receive input circuit. Sometimes these are implemented with differential (two balanced wires) and sometimes with single-ended circuitry (single wire referenced to a common chassis or ground).
This is the fundamental difference: in NMEA-2000 over 100 devices can be connected to the bus. In NMEA-0183 there can only be one sender on a circuit. There may be two or three receivers on a circuit, but that is about as far as you can stretch it without adding some buffering.
So again, to repeat my initial advice, you should not expect to be able to connect a NMEA-0183 device to a NMEA-2000 bus. I have tried to explain why, but, even if you don't follow the explanation, I don't believe that changes my answer.
NMEA 2000 and NMEA 0183 
