Yacht Devices NMEA 0183 User Manual - II. Nmea Basics

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II. NMEA Basics

This section describes the basics of NMEA 0183 and NMEA 2000 networks. We are recommend getting 

familiar with this section before connecting the Device.

These networks are very different at the electrical and software levels. NMEA 0183 also has traveled  

a long evolutionary path, but thanks to its simplicity and cheapness, it is still very popular and widely used.

1.  NMEA 0183

The default speed of a NMEA 0183 interface is 4800 baud. A high-speed interface is 38400 baud  

and was designed especially for AIS, but usually chart plotters and instrument displays allow any data  

(not only AIS) on a high-speed port. On a chart plotter, port speed can be configured in settings.

NMEA 0183 uses different wires for talking (transmitting, TX) and listening (receiving, RX) data. One 

talker can be connected to multiple listeners, but a listener can have only one talker connected. Special 

devices called “multiplexers” are used to join the output of multiple talkers to a single stream.

Figure 1. (a) RS-232 and (b) RS-422