NMEA 2000

NMEA 2000 is a network for data transmission and is mainly used in shipping. This data between different navigation devices are transmitted or multiple navigation equipment to a network together (GPS, depth sounder, log, wind gauge, compass, autopilot ). Also, control and monitoring of navigational data can be transmitted with it ( power generator, marine engine, control, fire alarm, etc ).

History

NMEA 2000 was developed in 2000 by the NMEA organization, as the successor to NMEA 0183rd NMEA 2000 is an extension of SAE J1939, which is used in commercial vehicles and is based on CAN (Intel, Bosch).

Properties and Configuration

NMEA 2000 is a network system (NMEA 0183 is only an interface and does not support network function). Up to 50 devices can be integrated and transmitter and receiver simultaneously. They communicate with 250 kbits (50 times faster than NMEA 0183 ) over a distance of up to 200 meters. 100 records can be transmitted simultaneously. NMEA 2000 configures itself Neither setup nor a central control unit are required. The system distinguishes between safety-related data and ordinary data. Unusual devices have no adverse effect on the overall system.

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

Interface

The devices are connected to a 4-wire shielded cable. Two twisted wires are used for power supply, two twisted wires transmit the data, the braided shield is ground. If more than two devices are connected, a "tee " at any point shall be inserted in the cable for each additional device and connected the device to it. The free cable ends are terminated with a pull-up resistor, it connects the two signal lines (121 Ω, 1%, 250 mW). The maximum distance between two tees is 100 m, the maximum cable length between the tee and the device ( drop cable ) is 6 m.

The plugs are not standardized. Each manufacturer uses different plug, some even have different plugs for different devices. The connectors are waterproof connected to the cables and are sold only as complete sets of cables.

Manufacturer

Major manufacturers, use the NMEA 2000 on some devices are: Furuno, Garmin, Lowrance, Navico, Raymarine, Simrad. Largest cable suppliers are Maretron and Molex connector coming from Turck and Amphenol-Air LB. Some manufacturers use their own connectors and are not NMEA 2000 certified. Therefore, the bus SimNet ( Simrad / Navico ) and SeaTalk NG ( Raymarine) called. With appropriate adapter cables but they are largely compatible with NMEA 2000.

Parameter group number (PGN )

Data are assigned to the NMEA -2000 standard a group number.