Actisense NSW-1-B User Manual
NMEA Autoswitch
NSW-1-B
User Manual
Issue 1.30
Automatic source prioritisation interface for use with the NMEA
0183 standard. Automatic selection of one NMEA data source from
multiple marine electronic devices / instruments
Personal computer (RS232) interface to NMEA 0183 standards
NMEA Autoswitch - NSW-1-B
Contents
Important Notices 4
Notices 4
Foreword 4
Introduction 4
General features 5
4 NMEA 0183 data input ports 5
An NMEA 0183 autoswitched data output port 5
A PC compatible RS-232 bi-directional port 5
Technical features 5
Software updates 5
Connecting devices together 6
The basics 6
The NMEA signals 6
The different NMEA standards 6
Connections 7
Connecting to NMEA devices 8
NMEA 0183 Inputs 8
NMEA 0183 Output 8
Other Connections 9
Connecting to a Personal Computer 9
Connecting to the battery supply 9
Troubleshooting guide 10
Diagnostic LED 10
Specifications 11
Company Information 12
Page 3© 2005 Active Research Limited
Actisense™
Important Notices
The Actisense™ NMEA Autoswitch (NSW-1) is intended
for use in a marine environment, primarily for below deck
use. If the NMEA Autoswitch (NSW-1) is to be used in a
more severe environment, such use may be considered
misuse under the seller’s warranty.
The Actisense™ NMEA Autoswitch (NSW-1) has been
certified to comply with the European directive for ElectroMagnetic Compatibility (EN60945), and is appropriately CE
marked. Operation of the unit should be in conjunction with
appropriate CE approved shielded connectors and cabling
used in accordance with the CE directive EN60945. Any
EMC related issues should be reported to Active Research
immediately to allow the company to rectify or resolve
EMC related problems in accordance with its obligations
under EN60945.
If the unit is connected such that compliance failure occurs
beyond the company’s control, the company shall not be
held responsible for compliance failure until suitable EMC
guidelines for connection are seen to have been taken.
Notices
When using this document, keep the following in mind:
The products described in this manual and the specifications
thereof may be changed without prior notice. To obtain upto-date information and/or specifications, contact Active
Research Limited 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 manual.
All rights are reserved: The contents of this manual may
not be transferred or copied without the expressed written
permission of Active Research Limited.
Active Research Limited will not be held responsible for
any damage to the user that may result from accidents
or any other reasons during operation of the user’s unit
according to this document.
As part of the autoswitch algorithm, the NSW-1 does
validate the NMEA sentence checksum and deletes/blocks
any sentences that fail this check. In addition, the NSW-1
also reads specific status indicators within particular NMEA
sentences in order to validate the input data stream as
a whole. However, the electronic device(s) supplying the
NSW-1 with NMEA data retain(s) the sole responsibility for
the NMEA data’s validity.
Foreword
Actisense™ recognises that instructions are often
skipped, so we have aimed to write this document in an
informative, yet direct manner that will aid the user. We
have tried to cover all the points a typical user may need
to know. Please read all sections before installing and
using the Actisense™ NMEA Autoswitch product and any
related software programs.
Introduction
The Actisense™ NMEA Autoswitch (NSW-1) has been
designed to automatically select the highest priority device
from up to 4 connected input devices. This creates a system
capable of automatically selecting the next priority device
if the higher priority device fails for one of three reasons: a
complete failure to send any NMEA data, an invalid NMEA
sentence checksum, or if the validity flag(s) contained
within the received NMEA sentence indicate that this data
is not valid and should only be used with caution.
The unique Actisense™ NMEA Autoswitch product has
evolved out of the requirement to solve two fundamental
problems with the existing marine industry NMEA 0183
communications standard.
The NMEA 0183 standard allows any suitably designed
marine electronic device to share its gathered information
with any other device on a vessel. Unfortunately, there
is one very large drawback with this standard - only one
device on a connected network can actually send data
(a single talker), with multiple devices (determined by
the current limit of the sending unit) listening to that data
(multiple listeners).
Secondly, for systems that have multiple NMEA devices of
an identical type (e.g. two GPS’s or two depth sounders),
automatic selection of the highest priority device is normally
a vital requirement. However, the NMEA 0183 standard
has no method of automatically switching between different
devices, so this requirement is usually fulfilled with a
manual changeover switch: not a very good solution, but
the only one available until now.
The Actisense™ NMEA Autoswitch solves both of
these problems by allowing up to 4 input devices/talkers,
connected through galvanic opto-isolated inputs, to be
analysed and the highest priority device’s NMEA data
always switched to a single output.
Full information on the complete Actisense™ product
range can be found on the Actisense™ website.
Page 4© 2005 Active Research Limited
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