NMEA 0183

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NMEA 0183

The National Marine Electronics Association (NMEA) is a US-based marine electronics trade organisation setting standards of communication between marine electronics.

NMEA 0183 is a combined electrical and data specification for communication between marine electronics such as echo sounder, sonars, anemometer, gyrocompass, autopilot, GPS receivers and many other types of instruments. It has been defined by, and is controlled by, the National Marine Electronics Association. It is slowly being phased out in favour of the newer NMEA 2000 standard, however many common devices support only NMEA 0183 and not NMEA 2000.

Introduction

The NMEA 0183 standard uses a simple ASCII, serial communications protocol that defines how data are transmitted in a "sentence" from one "talker" to multiple "listeners" at a time. Through the use of intermediate expanders, a talker can have a unidirectional conversation with a nearly unlimited number of listeners, and using multiplexers, multiple sensors can talk to a single computer port.

At the application layer, the standard also defines the contents of each sentence (message) type, so that all listeners can parse messages accurately.

Electrically most implementations of NMEA 0183 are functionally identical to a serial port running RS-232 (or EIA-232) which means that the protocol can be driven by a PC or laptop computer which normally has one or more serial ports and/or USB ports which can have serial to USB adapters attached.

Protocol Description

  • Each message's starting character is a dollar sign.
  • The next five characters identify the talker (two characters) and the type of message (three characters).
  • All data fields that follow are comma-delimited.
  • Where data is unavailable, the corresponding field remains blank.
  • There is an asterisk and checksum at the end of the message.
  • <CR><LF> ends the message.

The complete NMEA standard is proprietary and must be purchased from the NMEA at a cost of around US$250 as of June 2013. However, much of it has been reverse-engineered from public sources.

The best available public source for the NMEA 0183 protocol is NMEA Revealed by Eric S. Raymond.

Implementation on Board

Talkers

Listeners

Multiplexers

Wiring

Forum Discussions

List links to discussion threads on partnering forums. (see link for requirements)

External Links

References & Publications

Personal Notes

Personal experiences?


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