NMEA 2000 Interface

Last Updated on Friday, 11 June 2010 13:38 Written by Alison Little Wednesday, 12 May 2010 14:04

NMEA 2000 is a combined electrical and data specification for a marine data communication network between marine electronic devices such as depth finders, chart plotters, navigation instruments, and engines. It has been defined by, and is controlled by, the US based National Marine Electronics Association (NMEA) and is the successor to NMEA 0183.

NMEA 2000 connects devices using Controller Area Network (CAN) technology originally developed for the auto industry. It is based on the SAE J1939 high-level protocol, but defines its own messages. NMEA 2000 devices and J1939 devices can be made to co-exist on the same physical network.

The NMEA 2000 interface is supported by Ship Sim 3, AUV Sim, Airship Sim and by the RCW operator front-end software. The software outputs onto a NMEA 2000 bus using the NMEA 2000 specification 1.3 messages (PGNs). Data can also be received from the bus. The interface can be configured to enable and disable transmission and receipt of sentences and to set the transmission interval; individual sentences may be configured to include or remove information from the sentence.

Some messages can be used to report values or set demanded values, for example, PGN 127245 - Rudder, may be used to report rudder position or it may be used to set a rudder demand. It cannot do both simultaneously. The NMEA2000 interface therefore offer 2 modes: Command or Feedback. Most messages have only a single mode (Default). For navigational data sentences, the user is given the option of selecting the sensor whose data is used in the sentence,

Interfacing to a NMEA 2000 CAN Bus requires the use of a CAN Bus adaptor device. Only the EasySync USB2-F-7001 USB CAN Bus adaptor is supported at this time. This connects to the host PC via a USB connection and into a standard NMEA 2000 bus via a CAN cable (9-pin). Other CAN devices may be supported on request.

The CAN Bus 'snoop' facility which allows the user to view the information on the devices attached to the CAN Bus network.