NMEA 2000

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NMEA 2000 is a type of network for data transmission that is mainly used in the shipping industry. In NMEA networks, data is transmitted between different navigation devices or several navigation devices are combined to form a network ( GPS , depth gauge, log , anemometer, compass, autopilot). It can also be used to transmit control and monitoring data from the ship's command (power generator, ship's engine, control, fire alarm, etc.).

history

NMEA 2000 was developed in 2000 by the NMEA standards organization as the successor to NMEA 0183 . NMEA 2000 is an extension of SAE J1939 , which is used in the commercial vehicle sector and is based on the Controller Area Network (CAN) developed by Bosch and Intel .

Features and configuration

NMEA 2000 is a network system (NMEA 0183 is only an interface and does not support network functions). Up to 50 devices can be integrated and simultaneously senders and receivers. They communicate at 250 kbit / s (50 times faster than NMEA 0183) over a distance of up to 200 meters. 100 data records can be transferred simultaneously. NMEA 2000 configures itself. Neither a setup nor a central control unit is required. The system differentiates between security-relevant data and ordinary data. Failed devices have no disruptive influence on the overall system.

Most devices that are equipped with a NMEA 2000 interface go through a standardized test process and are "NMEA 2000 certified".

interface

typical NMEA 2000 network

The devices are connected with a 4-core shielded cable. Two twisted wires are used for the power supply, two twisted wires transmit the data, the braided shield is the grounding. If more than two devices are connected, a "T-piece" is inserted at any point in the cable for each additional device and the device is connected to it. The free cable ends are terminated with a terminal resistor, which connects the two signal lines (121 Ω, 1%, 250 mW). The maximum distance between two T-pieces is 100 m, the maximum cable length between T-piece and device (branch cable) is 6 m.

The plugs are not standardized. Each manufacturer uses different plugs, and some even have different plugs for different devices. The plugs are connected to the cables in a waterproof manner and are mostly sold as complete cable sets, but loose MicroC plugs are available.

colour Surname tension function
White CAN_High +2.5V signal
blue CAN_Low −2.5 V signal
metallic earth - shielding
red V + +12 V Power supply
black V− 0 V Power supply
exam
The network is correctly connected when the resistance between the two signal lines (white and blue) is between 50 and 60 ohms when the power supply is interrupted.
Power supply
The power supply usually only serves to supply display instruments and measuring instruments with low power consumption (anemometer, GPS, etc.). Larger electricity consumers are fed by their own power supply (chart plotter, depth gauge, autopilot, radar, etc.).
Dimensions
The cable system is usually not connected to the ship's earth so that insulation faults can be detected via an earth fault indicator before damage can occur in the power grid. The exception are smaller boats, where the neutral conductor is often connected to the hull directly at the power supply with a copper tape. If several power supplies are used, only one may be connected to ground; the 12 V line between the power supplies must then be interrupted.

Manufacturer

The most important manufacturers who use NMEA 2000 in their own devices are: Furuno , Garmin , Lowrance , Navico , Raymarine , Simrad and B&G . The largest cable suppliers are Maretron and Molex , connectors come from Turck and Amphenol-Air LB. Some manufacturers use their own connectors and are not NMEA 2000 certified. That is why the bus systems SimNet ( Simrad / Navico ) and SeaTalk NG ( Raymarine ) are called, but Simrad now also mainly uses the 5-pin MicroC connector that has become the de facto standard. With the appropriate adapter cables, however, they are largely compatible with NMEA 2000.

Group number parameter (PGN)

In the NMEA 2000 standard, data is assigned to a group number.

Network management
PGN Data
Acknowledgment basic
Acknowledgment group function
Address claim
Address, Commanded
Configuration information
Command group function
126996 Product information
Proprietary, Addressed
Proprietary, Global
126464 Received PGN List Group Function
059904 Request, basic
126208 Request group function
Transport Protocol, Connection Management
Transport Protocol, Data Transfer
126464 Transmitted PGN List Group Function
Application Data
PGN Data
127257 Attitude
129302 Battery status
129302 Bearing and distance between two marks
127501 Binary Switch Bank Status
129026 COG & SOG, Rapid Update
129283 Cross track error
130322 Current station data
date
129549 DGNSS Corrections
130577 Direction data
128275 Distance log
DSC call information
127489 Engine parameters, dynamic
127488 Engine parameters, rapid update
127497 Engine parameters, static
130311 Environmental parameters
127505 Fluid level
129556 GLONASS Almanac Data
129538 GNSS control status
129550 GNSS Differential Correction Receiver Interface
129551 GNSS Differential Correction Receiver Signal
129539 GNSS DOPs
129029 GNSS position data
129547 GNSS pseudorange error statistics
129542 GNSS pseudorange noise statistics
129545 GNSS RAIM output
129546 GNSS RAIM Settings
129540 GNSS Sats in View
129541 GPS Almanac Data Heading / Track Control
130053 Loran-C Range Data
130054 Loran-C Signal Data
130052 Loran-C TD Data
130323 Meteorological Station Data
130324 Moored Buoy Station Data
129284 Navigation data
129025 Position, rapid update
129799 Radio Frequency / Mode / Power
127245 Rudder
130321 Salinity Station Data
129291 Set & Drift, Rapid Update
130576 Small craft status
128259 speed
127502 Switch bank control
126992 System time
130320 Tide Station Data
126992 Time & Date
129301 Time to / from Mark
128520 Tracked target data
127493 Transmission parameters, dynamic
Trip parameters, small craft
129045 User date settings
127250 Vessel heading
130578 Vessel Speed ​​Components
128267 Water depth
130306 Wind data

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