Networking Marine Instruments: – 04 | NMEA 0183 to NMEA 2000 Conversion

Networking Marine Electronics

• Networking Marine Instruments: – 01 | Introduction
• Networking Marine Instruments: – 02 | NMEA 2000
• Networking Marine Instruments: – 03 | NMEA 0183
• Networking Marine Instruments: – 04 | NMEA 0183 to NMEA 2000 Conversion
• Networking Marine Instruments: – 05 | Connecting NMEA networks to a PC
• Networking Marine Instruments: – 06 | Marine Electronics Installation Guide
• Networking Marine Instruments: – 07 | Integrating Analogue Sensors
• Networking Marine Instruments: – 08 | Power Management and Network Reliability

Navigating NMEA 0183 to NMEA 2000 Network Connections

Most modern electronics devices for the marine market come with a NMEA 2000 (N2k) network interface. Along with navigation instruments, devices such as light switches, battery monitors, the sound system, intruder alarms, engine controls, etc., can all have N2k interfaces. Legacy products or those designed primarily for the commercial shipping market may only have NMEA 0183 interfaces.

Understanding NMEA 0183 to NMEA 2000 conversion is essential for integrating newer devices with older ones in the marine environment.

The method that these device interfaces use to communicate is very different at both the physical and software levels. NMEA 0183 is an older standard that uses a simple serial data protocol to communicate between marine electronics. It operates at a slower data rate and typically connects devices in a point-to-point configuration.

On the other hand, NMEA 2000 is a newer, more robust standard that allows for higher data rates and a more complex network topology. It uses a Controller Area Network (CAN) protocol, enabling multiple devices to communicate on a single network. For more information, see the previous articles in this series:

Part 2: Introduction to the parts of a NMEA2000 network

Part 3: Introduction to NMEA0183 networks

A little more background

NMEA 0183 communicates using human-readable sentences, which can be viewed on a simple serial terminal app (a good one is Coolterm). For example, a sentence could look like this:

⁠$GPGGA,123519,4807.038,N,01131.000,E,1,08,0.9,545.4,M,46.9,M,,*47

$GP shows that the sentence originates from a GPS receiver, the sentence name is GGA (Global Positioning System Fix Data) and includes time, position and quality of fix data.

                                                     11
       1         2       3 4        5 6 7  8   9  10 |  12 13  14   15
       |         |       | |        | | |  |   |   | |   | |   |    |
 $--GA,hhmmss.ss,ddmm.mm,a,ddmm.mm,a,x,xx,x.x,x.x,M,x.x,M,x.x,xxxx*hh<CR><LF>

N2k uses a framed binary data format. Let’s say that it is not human-readable and can’t be sent in a serial format, and requires specialist software to analyse. The N2k version of NMEA 0183 sentences are known as Parameter Group Numbers (PGNs). Each PGN contains specific data fields and is identified by a unique identifier, for example:

PGN 129029 – GNSS Position Data: This PGN contains the position data from the Global Navigation Satellite System (GNSS), including latitude, longitude, altitude, and position accuracy.

The Need for Conversion

Given the differences between NMEA 0183 and NMEA 2000, conversion between the two standards is often necessary when integrating older and newer devices. This conversion ensures that data can be shared across the network, allowing all devices to function harmoniously.

Conversion Methods

1. Using a Converter Device: The most straightforward method to convert between NMEA 0183 and NMEA 2000 is to use a dedicated converter device. This method will be covered in this article.
2. Via a Multiplexer: Some multiplexers have NMEA and 0183 interfaces and can be used as gateway devices.
3. Software Solutions: Some computer navigation applications support both NMEA 0183 and NMEA 2000 data streams and can be used to transfer data from one network to another. Interfacing with PC software will be the subject of the next article in this series. 

Using a Converter Device

A converter (often called a gateway) device is designed to translate data between NMEA 0183 and NMEA 2000 standards, ensuring compatibility and seamless communication between the two formats.

Selection

When selecting a converter device, it’s essential to ensure that it supports the specific data sentences used by your devices. Different converters will have varying capabilities, so it’s crucial to choose one that meets your specific needs. Converters are available as bi-directional or unidirectional. Unidirectional devices are typically cheaper and easier to install. 

Other considerations

• How waterproof does it need to be? Check the IP ratings.
• Type of connectors available: Do you need a Raymarine Seatalk^ng plug, for example?
• Type of NMEA 0183 connections: Does it have built-in terminal blocks or bare cable ends?

Installation

1. Securely mount the unit:
   • Mount the unit in a clean, dry place, and put drip loops in the cables.
   • All cables should be secured at a minimum of every 400mm to prevent cable damage due to movement and vibration.
2. Connect NMEA 0183 Devices
   • Identify the NMEA 0183 output from your device; refer to the manual.
   • If you need to extend cables, use one twisted pair, screened cable with about 0.5²mm conductors.
   • Connect the NME 0183 network output to the corresponding input on the converter device. Pay attention to getting the wires correctly matched (TX+ to RX+, TX- to RX-).
   • Double-check the wiring colour codes and for secure connections to avoid data transmission issues.
3. Connect NMEA 2000 Network:
   • Usually, this will be as simple as inserting a Tee connector into the backbone and hooking up the converter with a drop cable.

Configuration:

Data Sentences

Configure the converter to recognise and translate the specific NMEA 0183 sentences used by your devices. This may involve setting baud rates and selecting the appropriate data fields.

Network Settings

Configure the NMEA 2000 network settings to ensure proper communication between devices. This may include setting device addresses and ensuring compatibility with other networked devices. The procedure for changing addresses (instance numbers) varies among manufacturers and may be possible from your plotter or Multi-functional Display (MFD), or you may need to use specialist software.

The software is typically available as a free download from the manufacturer’s website. Some devices are configured using dip switches, which can be nice or limiting depending on your computer skills.

Avoiding data loops

A data loop describes the situation where information from one source is retransmitted by a second source, which then, if it appears at the input of the second source again, can be transmitted once more. This can result in severe network congestion. On NMEA 0183, this can easily happen when a multiplexer is used.

One way to avoid data loops between networks is to use a unidirectional device, such as those available from Quarc-elec, and not feed data back into your NMEA 0183 multiplexer from the converter.

Avoiding network overload

It is essential to avoid flooding a network with too much data. Typically, this occurs when translating from N2k to NMEA 0183 networks due to the amount of data that is present on the N2k network and possibly its update rate.

Consider a N2k network with a heading sensor attached, updating at 10Hz (10 times a second). If the heading sensor is a GPS compass, the data being transmitted at 10Hz may also include position, time, constellation data, rate of turn (ROT), position accuracy, roll, pitch and yaw information. If all of that data gets sent to the NMEA 0183 network, congestion is likely to occur, most likely in the form of corrupt or lost sentences. 

To avoid network overload, use the menus on your devices or the configuration software to turn off unused data sources or to prevent them from being repeated from one network to another.

Conclusion

By using a converter or gateway device, you can effectively bridge the gap between NMEA 0183 and NMEA 2000 networks, allowing for seamless communication and integration of marine electronics on your vessel. Beware of data loops and of flooding the NMEA 0183 network with unnecessary data.

Here are some converter/gateway devices that can help you interface between NMEA 0183 and NMEA 2000 networks:

I have included a ShipModul device in this table; it is significantly more expensive than the other devices, but it is a multiplexer/gateway device that supports NMEA 0183, NMEA 2000, and WiFi.

Image	Maker	Model	Galvanic Isolation	Configuration method	Ordering from New Zealand	Global price in USD
	Yacht Devices	YDNG-03N	yes	Free software Can Log Viewer OR text editor and micro SD card reader	From: Yacht Devices Australia $385.00 AUD	$189
	Actisense	NGX-1	yes	Free Software Actisense Toolkit	From: Marine Deals $549 NZD	$232
	Digital Yacht	iKonvert	yes	Dip switches	From: Marine Deals $379 NZD	$203
	Quark-elec	QK-AS01 Uni-directional 0183 to N2k	yes	Plug n play		$138
	Quark-elec	QK-AS00 Uni-directional N2k to 0183	yes	Plug n play		$138
	ShipModul	MiniPlex-3Wi-N2K	yes	Free software MPXConfig3	From: Marine Deals $839 NZD	$410

Recommended Books

There are very few books that cover marine electronics, but a few include some information alongside electrical information. These two are both good.

• Charlie Wing’s “Boatowners Illustrated Electrical Handbook” is excellent.

• Nigel Calder’s “Boatowners Mechanical Electrical Handbook” is not as good on the electrical and electronics side, but it is still a great reference to have aboard.

Note: These are Amazon associate links. If you buy via these links, it won’t cost you more, but I’ll get a small fee that helps me to maintain the site and put more time into generating content. Thank you.

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