NMEA 2000

Last updated

NMEA 2000, abbreviated to NMEA2k or N2K and standardized as IEC 61162-3, is a plug-and-play communications standard used for connecting marine sensors and display units within ships and boats. Communication runs at 250 kilobits-per-second and allows any sensor to talk to any display unit or other device compatible with NMEA 2000 protocols.

Contents

Details

Electrically, NMEA 2000 is compatible with the Controller Area Network ("CAN Bus") used on road vehicles and fuel engines. The higher-level protocol format is based on SAE J1939, with specific messages for the marine environment. Raymarine SeaTalk 2, Raymarine SeaTalkNG, Simrad Simnet, and Furuno CAN are rebranded implementations of NMEA 2000, though may use physical connectors different from the standardised DeviceNet 5-pin A-coded M12 screw connector, all of which are electrically compatible and can be directly connected.

The protocol is used to create a network of electronic devices—chiefly marine instruments—on a boat. Various instruments that meet the NMEA 2000 standard are connected to one central cable, known as a backbone. The backbone powers each instrument and relays data among all of the instruments on the network. This allows one display unit to show many different types of information. It also allows the instruments to work together, since they share data. NMEA 2000 is meant to be "plug and play" to allow devices made by different manufacturers to communicate with each other.

Examples of marine electronics devices to include in a network are GPS receivers, auto pilots, wind instruments, depth sounders, navigation instruments, engine instruments, and nautical chart plotters. The interconnectivity among instruments in the network allows, for example, the GPS receiver to correct the course that the autopilot is steering.

History

The NMEA 2000 standard was defined by, and is controlled by, the US-based National Marine Electronics Association (NMEA). Although the NMEA divulges some information regarding the standard, it claims copyright over the standard and thus its full contents are not publicly available. For example, the NMEA publicizes which messages exist and which fields they contain, but they do not disclose how to interpret the values contained in those fields. However, enthusiasts are slowly making progress in discovering these PGN definitions. [1]

Functionality

NMEA 2000 connects devices using Controller Area Network (CAN) technology originally developed for the auto industry. NMEA 2000 is based on the SAE J1939 high-level protocol, but defines its own messages. [2] [3] NMEA 2000 devices and J1939 devices can be made to co-exist on the same physical network. [4]

NMEA 2000 (IEC 61162-3) can be considered a successor to the NMEA 0183 (IEC 61162-1) serial data bus standard. [5] It has a significantly higher data rate (250k bits/second vs. 4800 bits/second for NMEA 0183). It uses a compact binary message format as opposed to the ASCII serial communications protocol used by NMEA 0183. Another improvement is that NMEA 2000 supports a disciplined multiple-talker, multiple-listener data network whereas NMEA 0183 requires a single-talker, multiple-listener (simplex) serial communications protocol.

Network construction

The NMEA 2000 network, like the SAE J1939 network on which it is based, is organized around a bus topology, and requires a single 120Ω termination resistor at each end of the bus. (The resistors are in parallel, so a properly terminated bus should have a total resistance of 60Ω). The maximum distance for any device from the bus is six metres. The maximum backbone cable length is 250 meters (820 feet) with Mini cable backbone or 100 meters (328 feet) with Micro cable backbone [3]

Typical NMEA 2000 Network Installation NMEA2000 Modified motor yacht.jpg
Typical NMEA 2000 Network Installation

Cabling and interconnect

The only cabling standard approved by the NMEA for use with NMEA 2000 networks is the DeviceNet cabling standard, which is controlled by the Open DeviceNet Vendors Association. Such cabling systems are permitted to be labeled "NMEA 2000 Approved". The DeviceNet standard defines levels of shielding, conductor size, weather resistance, and flexibility which are not necessarily met by other cabling solutions marketed as "NMEA 2000" compatible. [2] [3]

There are two sizes of cabling defined by the DeviceNet/NMEA 2000 standard. The larger of the two sizes is denoted as "Mini" (or alternatively, "Thick") cable, and is rated to carry up to 8 Amperes of power supply current. The smaller of the two sizes is denoted as "Micro" (or alternatively, "Thin") cable using the M12 5-pin barrel connector specified in IEC 61076-2-101, and is rated to carry up to 3 Amperes of power supply current.

Mini cable is primarily used as a "backbone" (or "trunk") for networks on larger vessels (typically with lengths of 20 m and above), with Micro cable used for connections between the network backbone and the individual components. Networks on smaller vessels often are constructed entirely of Micro cable and connectors.

An NMEA 2000 network is not electrically compatible with an NMEA 0183 network, and so an interface device is required to send messages between devices on the different types of network. An adapter is also required if NMEA 2000 messages are to be received by or transmitted from a PC.

NMEA-2000 cabling components incl. power-T N2K-CABLING.jpg
NMEA-2000 cabling components incl. power-T

Message format and parameter group numbers (PGNs)

In accordance with the SAE J1939 protocol, NMEA 2000 messages are sent as packets that consist of a header followed by (typically) 8 bytes of data. The header for a message specifies the transmitting device, the device to which the message was sent (which may be all devices), the message priority, and the PGN (Parameter Group Number). The PGN indicates which message is being sent, and thus how the data bytes should be interpreted to determine the values of the data fields that the message contains. [2]

Device certification

Devices go through a certification process overseen by the NMEA, and are permitted to display the "NMEA 2000 Certified" logo once they have completed the certification process. The certification process does not guarantee data content, that is the responsibility of the manufacturers. However, the certification process does assure that products from different manufacturers exchange data in a compatible way and that they can coexist on a network. [6]

NMEA 2000 and proprietary networks

Several manufacturers, including Simrad, Raymarine, Stowe, and BRP, have their own proprietary networks that are compatible with or akin to NMEA 2000. Simrad's is called SimNet, Raymarine's is called SeaTalk NG, Stowe's is called Dataline 2000, and BRP's is called CZone. Some of these, such as SimNet and Seatalk NG, are a standard NMEA 2000 network but use non-standard connectors and cabling; adapters are available to convert to standard NMEA 2000 connectors, or the user can simply remove the connector and make a direct connection. [7]

Trademarks

The term "NMEA 2000" is a registered trademark of the National Marine Electronics Association. Devices which are not "NMEA 2000 Certified" may not legally use the NMEA 2000 trademark in their advertising.

Manufacturers

The following are some of the companies that have registered with the NMEA for the purpose of producing NMEA 2000 certified products: [8]

See also

Related standards

Safety Standards using NMEA 2000

Misspellings

[14]

Related Research Articles

<span class="mw-page-title-main">USB</span> Standard for computer data connections

Universal Serial Bus (USB) is an industry standard that allows data exchange and delivery of power between many types of electronics. It specifies its architecture, in particular its physical interface, and communication protocols for data transfer and power delivery to and from hosts, such as personal computers, to and from peripheral devices, e.g. displays, keyboards, and mass storage devices, and to and from intermediate hubs, which multiply the number of a host's ports.

<span class="mw-page-title-main">GPIB</span> General Purpose Interface Bus (GPIB) specification

IEEE 488, also known as HP-IB and generically as GPIB, is a short-range digital communications 8-bit parallel multi-master interface bus specification developed by Hewlett-Packard. It subsequently became the subject of several standards.

NMEA 0183 is a combined electrical and data specification for communication between marine electronics such as echo sounder, sonars, anemometer, gyrocompass, autopilot, GPS receivers and many other types of instruments. It has been defined and is controlled by the National Marine Electronics Association (NMEA). It replaces the earlier NMEA 0180 and NMEA 0182 standards. In leisure marine applications, it is slowly being phased out in favor of the newer NMEA 2000 standard, though NMEA 0183 remains the norm in commercial shipping.

<span class="mw-page-title-main">CAN bus</span> Standard for serial communication between devices without host computer

A controller area network (CAN) is a vehicle bus standard designed to enable efficient communication primarily between electronic control units (ECUs). Originally developed to reduce the complexity and cost of electrical wiring in automobiles through multiplexing, the CAN bus protocol has since been adopted in various other contexts. This broadcast-based, message-oriented protocol ensures data integrity and prioritization through a process called arbitration, allowing the highest priority device to continue transmitting if multiple devices attempt to send data simultaneously, while others back off. Its reliability is enhanced by differential signaling, which mitigates electrical noise. Common versions of the CAN protocol include CAN 2.0, CAN FD, and CAN XL which vary in their data rate capabilities and maximum data payload sizes.

A vehicle bus is a specialized internal communications network that interconnects components inside a vehicle. In electronics, a bus is simply a device that connects multiple electrical or electronic devices together. Special requirements for vehicle control such as assurance of message delivery, of non-conflicting messages, of minimum time of delivery, of low cost, and of EMF noise resilience, as well as redundant routing and other characteristics mandate the use of less common networking protocols. Protocols include Controller Area Network (CAN), Local Interconnect Network (LIN) and others. Conventional computer networking technologies are rarely used, except in aircraft, where implementations of the ARINC 664 such as the Avionics Full-Duplex Switched Ethernet are used. Aircraft that use AFDX include the B787, the A400M and the A380. Trains commonly use Ethernet Consist Network (ECN). All cars sold in the United States since 1996 are required to have an On-Board Diagnostics connector, for access to the car's electronic controllers.

Society of Automotive Engineers standard SAE J1939 is the vehicle bus recommended practice used for communication and diagnostics among vehicle components. Originating in the car and heavy-duty truck industry in the United States, it is now widely used in other parts of the world.

RV-C is a communications protocol based on the Controller Area Network bus. The protocol is used in recreation vehicles to allow house and chassis components to communicate. RV-C is used for control, coordination, and diagnostics, in a multi-vendor environment.

A fieldbus is a member of a family of industrial digital communication networks used for real-time distributed control. Fieldbus profiles are standardized by the International Electrotechnical Commission (IEC) as IEC 61784/61158.

<span class="mw-page-title-main">ISO 11783</span> Computer network protocol

ISO 11783, known as Tractors and machinery for agriculture and forestry—Serial control and communications data network is a communication protocol for the agriculture industry based on, and harmonized with, the SAE J1939 protocol.

DeviceNet is a network protocol used in the automation industry to interconnect control devices for data exchange. It utilizes the Common Industrial Protocol over a Controller Area Network media layer and defines an application layer to cover a range of device profiles. Typical applications include information exchange, safety devices, and large I/O control networks.

Raymarine is a manufacturer and major supplier of electronic equipment for marine use. The company targets both recreational and light commercial markets with their products, which include:

The National Marine Electronics Association (NMEA) is a US-based marine electronics trade organization setting standards of communication between marine electronics.

Society of Automotive Engineers standard SAE J1708 is a standard used for serial communications between ECUs on a heavy duty vehicle and also between a computer and the vehicle. With respect to Open System Interconnection model (OSI), J1708 defines the physical layer. Common higher layer protocols that operate on top of J1708 are SAE J1587 and SAE J1922. The protocol is maintained by SAE International.

Marine electronics refers to electronics devices designed and classed for use in the marine environment on board ships and yachts where even a small amount of salt water can destroy some electronics devices. Therefore, the majority of these types of devices are either water resistant or waterproof.

The train communication network (TCN) is a hierarchical combination of two fieldbus for data transmission within trains. It consists of the Multifunction Vehicle Bus (MVB) inside each vehicle and of the Wire Train Bus (WTB) to connect the different vehicles. The TCN components have been standardized in IEC 61375.

IEC 61162 is a collection of IEC standards for "Digital interfaces for navigational equipment within a ship".

<span class="mw-page-title-main">USB-C</span> 24-pin USB connector system

USB-C, or USB Type-C, is a 24-pin connector that supersedes previous USB connectors and can carry audio, video and other data, e.g., to drive multiple displays or to store a backup to an external drive. It can also provide and receive power, such as powering a laptop or a mobile phone. It is applied not only by USB technology, but also by other protocols, including Thunderbolt, PCIe, HDMI, DisplayPort, and others. It is extensible to support future standards.

The initial versions of the USB standard specified connectors that were easy to use and that would have acceptable life spans; revisions of the standard added smaller connectors useful for compact portable devices. Higher-speed development of the USB standard gave rise to another family of connectors to permit additional data paths. All versions of USB specify cable properties; version 3.x cables include additional data paths. The USB standard included power supply to peripheral devices; modern versions of the standard extend the power delivery limits for battery charging and devices requiring up to 240 watts. USB has been selected as the standard charging format for many mobile phones, reducing the proliferation of proprietary chargers.

The GB/T charging standard is a set of GB/T standards, primarily in the GB/T 20234 family, for electric vehicle AC and DC fast charging used in China. The standards were revised and updated most recently in 2015 by the Standardization Administration of China. The term is an abbreviation of 国标推荐 (guóbiāo/tuījiàn), translated as "recommended/voluntary national standard".

References

  1. ↑ "Canboat". GitHub . 28 September 2021.
  2. 1 2 3 "NMEA 2000® explained white paper" (PDF). Archived from the original (PDF) on 2021-05-06. Retrieved 2021-05-24.
  3. 1 2 3 "Maretron NMEA 2000®Network Installation Guide" (PDF). Retrieved 2021-05-24.
  4. ↑ Bartlett Tim. Power & Motoryacht (ed.). "A Breakdown of Protocol: how boats' systems converse". Power & Motoryacht January 2012 issue. Retrieved 2015-09-25.
  5. ↑ boatprojects.blogspot.com, ed. (4 December 2012). "Beginners guide to Nmea 2000, Nmea 0183, and bridging" . Retrieved 2015-09-25.
  6. ↑ "NMEA 2000® Certification Process Overview and License Agreement" (PDF). Archived from the original (PDF) on 2016-04-09. Retrieved 2017-06-23.
  7. ↑ N2K, cable mixing not a big woop, Panbo, Feb 2008
  8. ↑ "NMEA registratered manufacturers" . Retrieved 2023-04-01.
  9. ↑ Actisense website
  10. ↑ "NMEA 2000® Brad® Micro-Change® (M12) and Brad® Mini-Change® Cables and Connectors" . Retrieved 2013-11-30.
  11. ↑ "Hemisphere GNSS Marine Products" . Retrieved 2015-01-26.
  12. ↑ "Warwick Control Technologies Marine Kit" . Retrieved 2018-04-27.
  13. ↑ "Böning Website" . Retrieved 2024-01-12.
  14. ↑ "NMEA 2000/0183 Bi-directional Gateway + WiFi". Quark-elec NMEA 2000/0183 Bi-directional Gateway.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.