Actisense
®
Page 4© 2007 Active Research Limited
Important Notices
This Actisense document is for informational purposes
only, and to the best of our knowledge, the information
contained within is accurate and true. Any use of the
information contained within this document is solely at the
user’s own risk.
No responsibility will be accepted for any personal injury
or damage to a boat or its connected equipment resulting
directly or indirectly from information contained within.
Navigational equipment used on board a boat can be
critical to the safe passage of the vessel, so if in doubt,
contact an expert equipment installer before making any
modications to your current system.
Unfortunately, we cannot published the entire NMEA 0183
standard here, as it is copyrighted by NMEA. A full copy of
this standard is available for purchase at the NMEA web
site - see the NMEA contact details at end of document.
We would recommend anyone designing equipment for
connection to an NMEA 0183 network to obtain an ofcial
copy.
Notices
When using this document, keep the following in mind:
The information contained in this document and any
specications thereof may be changed without prior notice.
To obtain up-to-date information, contact Active Research
Limited (refer to the Contact Information section) or visit
the Actisense website (www.actisense.com).
Active Research Limited will not be liable for infringement
of copyright, industrial property right, or other rights of a
third party caused by the use of information or drawings
described in this document.
All rights are reserved: The contents of this document may
not be transferred or copied without the expressed written
permission of Active Research Limited.
Feedback!
This document has been produced from some of the
knowledge and experience gained by Actisense from
many years of experience in NMEA interfacing.
Please report any errors, omissions or inaccuracies
directly to Actisense - we intend this document to be
a useful resource tool to installers new to NMEA 0183
and inevitably we may have missed out the vital piece
of information that they may have required to achieve a
working NMEA 0183 system.
NMEA 0183 Introduction
The National Marine Electronics Association (NMEA)
developed a standard over 20 years ago that denes the
interface between various pieces of marine electronic
equipment and navigational computers, allowing them to
talk together and share vital information.
The NMEA 0183 standard slowly became the common
method by which marine electronics devices could
talk to one another. The standard species both the
electrical connections that make up an NMEA system,
the communications method of transmitting the data, and
the format of the data sentences that carry the NMEA
information.
The NMEA 0183 standard is a purely digital data
transmission scheme, using ‘1’s and ‘0’s in a binary format,
to communicate a digital representation of the required
information (depth, speed etc.) to a connected device.
The need for NMEA 0183 evolved from the earlier “NMEA
0180” and “NMEA 0182” standards. Because they differ in
baud rate and transmission parameters from NMEA 0183,
they are completely incompatible with NMEA 0183.
Similarly, the new “NMEA 2000” standard is totally
different, and the two networks cannot be mixed without
using a special gateway device to convert between the
two standards (the new Actisense NMEA 2000 Gateway).
The basics
The NMEA standard denes the electrical signalling, data
protocol and sentence formats for a 4800 baud serial data
bus.
NMEA data is transmitted from an information source such
as a GPS, depth sounder, or gyro compass etc. These
data sending devices are called “Talkers”.
Equipment receiving this information such as a chart-
plotter, radar, PC or NMEA display is called a “Listener”.
Each NMEA 0183 data bus shall have only a single talker
but may have many listeners. The talker section of this
document explains why this is the case.
