navCenter Dual Data Streams

Pilot Remote Control

navCenter defaults to directing autoPilot commands to the Primary Data Stream.

When the Secondary Stream is activated navCenter is able to direct autoPilot commands to either the Primary or Secondary Data Stream.

The Pilot Type is automatically set depending on the Format being used by the selected data stream and it is not possible to change this selection unless the Protocol being used by the data stream selected is iConnect Client.

Then, as navCenter is unable to determine the Protocol being used by the iConnect Server, Pilot Type must be set manually.

Here we can see that the Secondary Stream has been activated and has been selected as the target Destination for autoPilot commands.

As the Secondary Stream is using Format NMEA0183 Pilot Type has been set to SeaTalk1.

SeaTalk NMEA Header has been initially set to STALK but this may be changed to PSMDST if required by the Gateway being used.

Using Dual Data Streams

The diagram above depicts the possible evolution of a vessel's instruments system.

The original SeaTalk1 / NMEA0183 system is shown outlined in green.

• A Gateway has been installed which is connected to the SeaTalk1 databus and to NMEA0183 data source(s)
• There are no official NMEA0183 sentences defined to control an SeaTalk1 autoPilot. The Gateway performs bi-directional conversion between SeaTalk1 and NMEA0183 data using Sentence $PSMDST or the unofficial Sentence $STALK to carry the SeaTalk1 data.

navCenter is connected to the Gateway's WiFi system and is able to:

• Access and display all of the data available on the SeaTalk1 and NMEA0183 databuses
• Control the SeaTalk1 autoPilot by transmitting $STALK/$PSMDST sentences to the Gateway which in turn converts the sentences in SeaTalk1 commands which it places onto the SeaTalk1 databus

NMEA2000/SeaTalkNG (N2K) instruments are now added to the vessel

In order for the data from the N2K instruments to be accessable by the SeaTalk1/NMEA0183 system it has been a common practice to install a device which converts N2K data to NMEA0183. This conversion device and the N2K instruments are shown outlined in blue.

Now the original SeaTalk1/NMEA0183 instruments and navCenter are able to access the converted N2K data and if the N2K/NMEA0183 converter is bi-directional the converted SeaTalk1/NMEA0183 data would be available to the N2K instruments and autoPilot.

What happens when we need to replace the SeaTalk1 autoPilot with a modern SeaTalkNG autoPilot?

This addition is shown outlined in orange.

The Raymarine controls for the SeaTalkNG autopilot may sited alongside the existing instrumentation and converter connecting the two databuses should ensure that data continues to be shared.

However navCenter is not able to control the SeaTalkNG autoPilot. This is because there are no existing NMEA0183 sentences defined which are able to control a SeaTalkNG autoPilot and thus it is impossible for the converter to derive SeaTalkNG autoPilot commands from NMEA0183 sentences.

The only way for an app like navCenter to be able to control a SeaTalkNG autoPilot is by connecting, via WiFi, to a Gateway that that connects directly to the N2K databus and offers bi-direction transmission of N2K PGNs.

So if we want navCenter to be able to control the SeaTalkNG autoPilot you need to buy another Gateway🫤.

This is the unfortunate position that many people have found themselves in.

At this point it is worth noting that Gateway manufacturers may say of their Gateway something like this "allows control of Raymarine SeaTalk NG autopilots via NMEA0183 sentences".

Statements like this are misleading as what they actually mean is that they are able to convert NMEA0183 sentences (generally from a plotter) into equivalent N2K PGNs so that when a SeaTalkNG autoPilot is in TRACK mode a plotter is able to send the data required to enable the autoPilot to follow a route using information derived from NMEA2000/NG or NMEA0183 sentences.

The following link contains helpful information from Raymarine which explains this situation: Commands required to operate Track mode

In other words a Plotter may passing routing information to your autoPilot but it has no control over what the autoPilot does with that information.

Consequently you cannot change the mode (AUTO/STANDBY etc.) or the heading of your SeaTalkNG autoPilot using the above approach.

navCenter emulates Raymarines autoPilot remote control and thus is able to change the mode and heading of the autoPilot.

Consider An Alternative Upgrade Path

If you are adding N2K instruments and/or an N2K autoPilot to an existing SeaTalk1/NMEA0183 system it is possible to take another approach.

Consider carefully whether or not you really need the N2K data to be accessable by your existing SeaTalk1/NMEA0183 instruments and vice versa. Or whether it is sufficient to site the new instrument displays alongside the existing instrumentation.

If you decide that sharing data between the systems is not strictly necessary then instead of installing a converter there are two options that you could consider:

1. Retain your existing gateway to handle the SeaTalk1/NMEA0183 data and purchase an inexpensive WiFi Gateway that can handle bi-directional N2K data over a single server.
2. Replace your existing Gateway with a more sophisticated (and therefore more expensive) Gateway that is able to connect simultaneously to SeaTalk1, SeatalkNG/N2K and NMEA0183 databuses and offers at least two Server / Port outputs.

You will find a list of Gateways here

Taking either of the above options enables you to be able to:

• Assign the Primary Data Stream to your existing SeaTalk1/NMEA0183 Gateway or the NMEA0183 Server on your new Gateway
• Assign the Secondary Data Stream to your NMEA2000/NG data via a dedicated NMEA2000 Gateway or the NMEA2000 Server on your new gateway
• Assign The Pilot Destination to the Primary Stream

Then navCenter be able to:

• Display all of your SeaTalk1, NMEA0183, NMEA2000/NG data
• Control your existing SeaTalk1 autopilot

Both Data Streams will be seamlessly merged by navCenter. By taking this approach you will save the cost of a converter. Though, of course, you have had to buy another Gateway but a simple NMEA2000/NG Gateway can be purchased for considerably less than most converters.

If you wish to share NMEA0183 / NMEA2000/NG data between your instruments you can still add a converter for a complete solution.

However, the advantage of taking this approach becomes apparent should you decide or need to replace your SeaTalk1 autoPilot with a SeaTalkNG autoPilot.

Then you would simply assign navCeter's Pilot Destination to the NMEA2000/NG Stream and you would be able to see all of your NMEA data and be able to control your SeaTalkNG autoPilot from navCenter without any further hardware purchases.