Understand different protocols - SeaTalk1 & SeaTalkNG

In the marine industry, there are a number of different data formats and protocols that are used. The purpose of this article is to help clarify the common ones!
When working with marine electronics there are four common data formats that you will hear about. These är;

• SeaTalk1
• SeaTalkNG
• NMEA 0183
• NMEA 2000

So, what are these, and what do they mean when you install devices on your boat?

SeaTalk1
There is a common misconception that SeaTalk1 (ST1) is NMEA 0183, but it ä not the case. SeaTalk 1 is a proprietary system designed by Raymarine. Even if they both work on a serial data protocol, NMEA 0183 and ST1 share no other similarities.

SeaTalk uses 3 wires as a connection method, which are paralleled across all devices. The 3 wires are as follows;

• 12V Supply
• GND / Common Supply
• Data (serial)

Since both messages and wiring are different from NMEA 0183, they are not directly compatible, but it is possible to use an ST1 to NMEA 0183 converter. SeaTalk1 units are still common on boats, and while some of them work on its own ST1 network where the devices are interconnected and communicate bi-directionally, others work together with a 0183 converter.

Unfortunately, there is no direct conversion between ST1 and NMEA 2000, so ; the process would require an ST1 to NMEA0183 gateway and then the Actisense NGW-1 bidirectional conversion gateway to convert this to NMEA 2000.




NGW-1-STNG NMEA 2000 Gateway (SeaTalk NG)

NMEA 0183
NMEA 0183 is the non-proprietary "standard" message format and protocol for most marine electronics manufactured prior to NMEA 2000. There are two; types of NMEA 0183 – "old" (version 1.5) and a current version (2.0+) Version 1.5 uses RS232 device specification for connection, and the current protocol uses RS422 (differential). The principle between the RS232 and RS422 versions is the same, and the data is almost identical.

The biggest change between v1.5 and v2.0+ data is is the addition of checksums on The NMEA 0183 sentences. Before 2.0+ it was not mandatory to have a checksum at the end of the sentence, but this was changed when 2.0 was implemented.
Usually this does not cause too much conflict between NMEA 0183 units, but it can there are some problems in specific scenarios. For example, if the speaker is v1.5 and the listener is v2.0+ and only treats sentences as valid if they contain a checksum, it will ignore the v1.5 speaker.

NMEA 0183 v2.0+ Differential units use a 4-wire connection with a transmit and receive pair, usually marked "+/A" and "–/B" or "Tx" and "Rx" . The protocol uses ASCII Serial, and has low speed and works at 4800bit/sec.
Converting NMEA 0183 to NMEA 2000 is a very simple process with a conversion gateway which is NGW-1. It is also possible to convert NMEA 2000 to NMEA 0183 with our gateway.




SeaTalkNG & NMEA 2000
NMEA 2000 is the successor to NMEA 0183, which works on; a binary message format with a much higher speed of 250k bits/sec. Unlike NMEA 0183 which uses a single-speaker/multi-listener setup, NMEA 2000 uses CAN (Controller Area Network), creating a multi-speaker/multi-listener network where each device communicates together.
When it comes to NMEA 2000 and SeaTalkNG (STNG), there is a bit of confusion about the two, and we often get asked if they are the same. will work together. På data format/protocol levelå Both of these are identical. NMEA 2000 and STNG both work with the CAN protocol and use exactly the same messages (PGN). In fact, the only difference between the two; Is the physical layer.

NMEA 2000 uses the DeviceNet standard for cables and connectors, where M12 male and female connectors are used to connect the cables and connectors. SeaTalkNG uses Raymarine's proprietary cabling system, which does not follow the DeviceNet standard. However, connecting STNG cables and NMEA 2000 cables is very easy, as Raymarine sells adapter cables. The adapter cable A06045 can alsoå purchased as part of a package with our NMEA 2000 products (cable not sold alone).

In short, this means that there is no "conversion from STNG to NMEA 2000", but only an adapter cable is needed to join the two.


STNG cable