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Introduction
The MiniPlex-3 series NMEA multiplexers enable connection of multiple NMEA 0183/2000 devices and a
host device like a PC, a laptop or a tablet. All models share the same number of NMEA ports and feature
set. They differ in host interface type, the interface that talks to the computer. Some models also have
an NMEA 2000 interface.
This manual covers all models of the MiniPlex-3 series. There is a chapter for each type of host port. The
remaining part of the manual covers NMEA 0183 and NMEA 2000 connections and configuration, which
are the same for all models.
NMEA 0183
The National Marine Electronics Association (www.nmea.org) has defined a communication protocol called
NMEA 0183, which enables navigation instruments and devices to exchange data with each other.
Using the NMEA 0183 protocol, an electronic compass can send a heading to a radar to enable a north-up
display. Similarly, a GPS can send a course to steer, cross-track error and other related information to an
autopilot to steer a boat to a set waypoint in the GPS.
NMEA 0183 Sentences
The NMEA 0183 protocol defines human-readable text sentences with a strictly defined format. These
sentences can be seen in MPXConfig3, in the top half of the window, and look like the sentences below:
$GPGGA,143357.999,5301.0061,N,00635.5479,E,1,06,1.9,90.0,M,,,,0000*39
$GPGLL,5301.0061,N,00635.5479,E,143357.999,A*22
$HEHDT,67.0,T*1E
A receiving device or software application will know that a sentence starting with $GPGLL originates from
a GPS (hence the GP at the beginning of the sentence) and that it contains the geographic longitude and
latitude (GLL). The $GPGLL part in this example is called the address field of a sentence.
Talkers and Listeners
The NMEA 0183 standard defines talkers and listeners. A device that sends information is a talker and a
device that receives information is a listener. When connected to each other, the talker sends information
to the listener.
Communication using the NMEA 0183 protocol involves at least one talker
sending data to one listener. Figure 1 on the right shows such a minimal
system: a gyrocompass sends heading data to a radar.
It is important to know that a talker or listener port is named after its
function, not after what it is connected to. So, a talker port transmits
information, and it is connected to a listener port which receives information. This might be confusing at
times so further in this manual we will use the terms input and output instead of listener and talker port
respectively.
The NMEA 0183 standard specifies that an output should have enough driving capacity to talk to four
listeners. This is as easy to achieve as telling a story to an audience of four people; the only requirement
is to talk loud enough.
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