What it is and how it works.

What is is and how it works.

NMEA 0183 (National Marine Electronics Association 0183) is a standard communication protocol used in the marine industry for interfacing and exchanging data between various marine electronic devices and systems on boats and ships. It provides a common language for devices from different manufacturers to communicate with each other, enabling seamless integration of navigation, communication, and entertainment systems onboard vessels.



Here are some key points about NMEA 0183:

  1. Serial Communication: NMEA 0183 uses serial communication to transmit data between devices. It typically operates over RS-422 or RS-232 serial connections, using standard voltage levels and signaling protocols. This allows for simple, point-to-point or point-to-multipoint connections between devices.

  2. Message Format: NMEA 0183 defines a set of standardized message formats for transmitting different types of data, such as GPS position, speed, heading, depth, wind speed, and more. These messages are formatted as ASCII text strings, with specific data fields separated by commas and enclosed within dollar sign ($) and carriage return/line feed characters.

  3. Data Sentences: Each NMEA 0183 message is referred to as a “sentence,” and each sentence begins with a two-letter “talker identifier” that specifies the type of device transmitting the message (e.g., GP for GPS receiver, AP for autopilot, MW for wind sensor). The sentence is followed by a three-letter “sentence identifier” that indicates the type of data being transmitted (e.g., GGA for GPS position data, RMC for recommended minimum navigation information).

  4. Point-to-Point Connections: NMEA 0183 devices are typically connected in a daisy-chain or star network topology, with one device acting as a “talker” that transmits data and one or more devices acting as “listeners” that receive and process the data. This allows for simple, direct connections between devices without the need for complex network configurations.

  5. Baud Rate and Voltage Levels: NMEA 0183 devices typically operate at baud rates of 4800 or 9600 bits per second (bps), although higher baud rates are also supported for faster data transmission. Voltage levels for RS-422 connections are typically +/- 5V, while RS-232 connections use voltage levels of +/- 12V.

  6. Limitations: While NMEA 0183 is widely used and relatively simple to implement, it has some limitations compared to newer standards such as NMEA 2000. These include slower data transfer rates, limited device compatibility, and the need for separate wiring for each device connection. Additionally, NMEA 0183 networks can become complex and difficult to manage as the number of connected devices increases.

Despite its limitations, NMEA 0183 remains a popular and widely supported communication protocol in the marine industry, particularly for smaller vessels and older systems where compatibility with existing equipment is important. It continues to be used in a wide range of marine electronic devices, including GPS receivers, chartplotters, autopilots, depth sounders, and AIS transponders.