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NMEA/Autopilot Output from Maptech Navigation Computers

Created: 09/15/2006
Modified: 01/11/2007

TOPIC

Wiring instructions, required parts, etc.


DISCUSSION

Introduction
The NMEA/Autopilot Output from Maptech Navigation Computers is designed to pass through heading, position, and other navigation data from the GPS and computer to other NMEA devices (such as an Autopilot.) This document explains the conditions under which this pass through will take place, what NMEA sentences are passed through, and how to make the appropriate connections.


Pass-through from the GPS
So long as the GPS is powered on and connected properly while the chart plotting software is in use, streaming NMEA data from the GPS will be passed through to the NMEA/Autopilot output on the Navigation Computer. In most installations, this will consist exclusively of the RMC NMEA sentence. Please note that the chart plotting software must be running in order to guarantee this pass-through. Most navigation computers are configured to pass data through, regardless of the use of the chart plotter - however this connection is not always present. For specifics, please see the "connections" section for each type of Navigation Computer, below.


Following A Route
Once the chart plotting software is started and a route is being followed, additional sentences (designed for steering an Autopilot) are added to the streaming output. As of version 3.02 of the chart plotting software, these NMEA sentences are: APB, BWR, VTG, and BWC.

Please note that these sentences will not appear in the NMEA output unless the operator of the Navigation Computer has elected to follow a route. This can be an existing, stored route, or an "Instant Waypoint." Regardless, RMC will always be passed through from the GPS, so long as the GPS is receiving a valid fix and connected properly and the chart plotting software is in use.


Making the Connections
Maptech Navigation Computers consist of three "Types." If you are unsure as to the type of Navigation Computer installed on your vessel, please refer to this technical document.

Connections: Type I
The connections to and from a Type I Navigation Computer go through a "cable kit" that consists of 1 connection to the computer, 2 connections to the power supply, 1 connection to the power source, and one to the autopilot. Refer to the following diagram for details.
TYPEI_HOOKUPS.JPG

The Black autopilot wire is NMEA Negative (-) and the White wire is NMEA Positive (+). These transmit the NMEA data to the Autopilot not only when the chart plotting software is in use, but also pass through the GPS signal when the plotting software is not in use.

Connections: Type II
The Autopilot connection on a Type II Navigation Computer is made through the "power supply." Maptech part 105-0204 is the cable that connects to the power supply and ends in 3 wires: red, black, and white. The Black autopilot wire (connected to pin 3 on the power supply) is NMEA Negative (-) and the White wire (connected to pin 4 on the power supply) is NMEA Positive (+). These transmit the NMEA data to the Autopilot not only when the chart plotting software is in use, but also pass through the GPS signal when the plotting software is not in use. The red wire is not used and should not be connected.

Connections: Model 300
The Autopilot connection on a Model 300 (312 or 315) Navigation Computer is made via a DB9 connector located on the bottom of the display. It has an orange label which indicates: "NMEA I/O - AutoPilot." Maptech parts 305-0204 (6 ft.,) 305-0205 (30 ft.,) and 305-0206 (60 ft.,) are used to interface with this connector. Please note that this is not a "standard" DB9 connection - instead, an alternative pin out is used.

The Autopilot cable terminates in 4 wires. Depending on the revision of the cable, it will be terminated as follows:

OLDER STYLE:
Old style cables end with 4 wires: Black, Red, Blue (or Green), and White. The Black autopilot wire (connected to pin 1 on the DB9 connector) is NMEA Negative (-) and the White wire (connected to pin 4 on the DB9 connector) is NMEA Positive (+). These transmit the NMEA data to the Autopilot only when the chart plotting software is in use. The other two wires (Red, NMEA +, pin 2; and Blue/Green, NMEA -, pin 3) allow NMEA data to be transmitted back to the Navigation Computer. Other devices, such as an electronic compass, can be connected to the Autopilot with its data passed back to the Navigation Computer through the Red and Blue/Green connections. However, it is strongly recommended that a General I/O Cable (described below) is used if this function is desired.

NEWER STYLE:
New style cables end with 4 wires: Black and White (paired together with a White shielding), and Black and Red (paired together with a Red shielding.) The Black and White pair is the NMEA output to the Autopilot. In this pairing, the Black autopilot wire (connected to pin 1 on the DB9 connector) is NMEA Negative (-) and the White wire (connected to pin 4 on the DB9 connector) is NMEA Positive (+). These transmit the NMEA data to the Autopilot not only when the chart plotting software is in use, but also pass through the GPS signal (RMC strings, only) and Depth readings when the plotting software is not in use. The Black and Red pair is the NMEA input from the Autopilot. In this pairing, the wires (Red, NMEA +, pin 2; and Black, NMEA -, pin 3) allow NMEA data to be transmitted back to the Navigation Computer. Other devices, such as an electronic compass, can be connected to the Autopilot with its data passed back to the Navigation Computer through the Red and Black connections. However, it is strongly recommended that a General I/O Cable (described below) is used if this function is desired.

Connections: Accessories (General I/O Cable)
On Model 300 installations, use a General I/O Cable to interface other devices (such as an electronic compass) to the navigation computer. This cable has a White sleeve and is available in 6ft (Maptech Part 305-0224), 30ft (305-0225), and 60ft (305-0226) lengths. When installing this cable, be sure to set the appropriate entries in the NavPanel's PROFile settings to match the COM Port chosen for input of external accessories.

Please note that a General I/O Cable *must* be used when receiving compass headings via a Raymarine autopilot. Otherwise, the high speed of the data provided will interfere with the ability to decode the rest of the NMEA devices (such as GPS and Depth.)


Related Technical Documents:
- Determining Type by Serial Number
- Model 312 Navigation Computer - Hardware drawings, templates, etc. for Sea Ray Navigator
- Model 312 Navigation Computer - Hardware drawings, templates, etc. for i3 Navigator
- Model 300 (312 & 315) Autopilot Cable Installation Instructions
- Model 300 (312 & 315) COM Port I/O High Speed Compass Input Cable - Installation Guide
- Type II Navigation Computer - Installation Guide
- Type I Navigation Computer - Owner's Manual





 


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