AIS, NMEA and Baud Rates

[Old Bumbulum]

I have a Seatech IAS 6 that I am trying to interface to SEATALKNG via an Actisense converter. The NMEA 0163 side of the Actisense unit isn't responding.

Does anyone know if the IAS 6 can have it's Baud rates reprogrammed or are they fixed? (talk and listen are on different rates and the Actisense only works on one rate - even if you can figure out how to reprogramme the damn thing.

The alternative is to buy a second Actisense unit (for yet another £110) in order to get 2 way communication, a very expensive and surely unnecessary workaround.

Ideas?

 

[pvb]

Does anyone know if the IAS 6 can have it's Baud rates reprogrammed or are they fixed? (talk and listen are on different rates and the Actisense only works on one rate - even if you can figure out how to reprogramme the damn thing.

Looks like they're fixed.

 

[laika]

Plan B:
- Set the Actisense to 38400 and use it on the output from the AIS
- Buy a cheap, dedicated GPS for less than half the cost of another ngw1 and use it to feed 4800 GPS data to the AIS (and possibly vhf or another thing you need nmea-0183 gps for)

 

[pvb]

Plan B:
- Set the Actisense to 38400 and use it on the output from the AIS
- Buy a cheap, dedicated GPS for less than half the cost of another ngw1 and use it to feed 4800 GPS data to the AIS (and possibly vhf or another thing you need nmea-0183 gps for)

I think the OP maybe wants to display instrument data on the AIS6.

 

[lpdsn]

... and the Actisense only works on one rate - even if you can figure out how to reprogramme the damn thing.

The alternative is to buy a second Actisense unit (for yet another £110) in order to get 2 way communication, a very expensive and surely unnecessary workaround.

Ideas?

I believe you're right that although you can change the rate on the Actisense it is the same baud rate for input and output.

I presume the AIS traffic isn't the issue but rather getting data from STNG into the IAS6?

If you do resort to a second Actisense (you shouldn't have to) I've one (AIS version) I replaced with a ShipModul Miniplex and I'd sell it for a fair bit less than £110.

 

[Old Bumbulum]

I think the OP maybe wants to display instrument data on the AIS6.

Correct. He did!

Just to confuse the issue I found this www.seatec.de/technology/elektronik that says AIS6 baud rate is 34,800!

How on earth do I find out which I've actually got?

Reprogramming the Actisense unit is a serious geek's job and not something most people can do.

lpdsn, that's a kind thought - hang onto it I may yet need another one!

L

 

[lpdsn]

OK, I've found an AIS-6 manual. It seems the four NMEA inputs are all 4.8Kb. And the output is 38.4Kb (AIS + multiplexed inputs). Based on a quick scan I don't believe they can be changed.

I presume you're trying to get the AIS data to the STNG network and are succeeding at that.

What else is it you are trying to do? STNG sourced instrument data to display on the AIS-6 as pvb suggests?

 

[pvb]

Just to confuse the issue I found this www.seatec.de/technology/elektronik that says AIS6 baud rate is 34,800!

I can't see that in the document you linked to. The standard baud rate for AIS data is 38400.

 

[Old Bumbulum]

Naturally I'm trying to get AIS data on the SEATALKNG chartplotter and instrument data from the sesatalk onto the AIS below decks.

Actisense technical (who are very helpful) say they've never heard of an AIS that ran at two different baud rates, nor one that didn't run at 38,400.

Yet the data on the german website I posted above says it is 38,400?

So far all I've managed is to get the NMEA2000 light only flashing on the NGW1 but no data transferred at all - not surprising if it is trying to talk at 38,400 but the AIS is on something else!

Flummoxed!

 

[lpdsn]

So far all I've managed is to get the NMEA2000 light only flashing on the NGW1 but no data transferred at all - not surprising if it is trying to talk at 38,400 but the AIS is on something else!

Have you got it working in neither direction? It should be easy to get the 38.4Kb output into the Actisense and out to the STNG bus. I presume you have the AIS version of the Actisense or have re-programmed the one you've got suitably.

Even if you do manage to feed data in from STNG via the Actisense you've still got a problem as you will have a data loop. What you feed in to the AIS-6 at 4.8Kb is multiplexed and sent out at 38.4Kb so it'll go back onto the STNG bus. You can usually deal with multiple sources but that will be another task for you to plan for all the relevant boxes on the STNG bus.

To be honest I would not say that the AIS-6 AIS functionality runs at two different baud rates. It provides AIS at 38.4Kb. (<- that's a full stop.) It has other non-AIS functionality that runs at 4.8Kb. So Actisense still haven't heard of an AIS that runs at two baud rates.

 

[pvb]

Yet the data on the german website I posted above says it is 38,400?

It does, that's the standard speed for AIS equipment, they all use 38400 baud!

 

[Old Bumbulum]

Have you got it working in neither direction? It should be easy to get the 38.4Kb output into the Actisense and out to the STNG bus. I presume you have the AIS version of the Actisense or have re-programmed the one you've got suitably.

Even if you do manage to feed data in from STNG via the Actisense you've still got a problem as you will have a data loop. What you feed in to the AIS-6 at 4.8Kb is multiplexed and sent out at 38.4Kb so it'll go back onto the STNG bus. You can usually deal with multiple sources but that will be another task for you to plan for all the relevant boxes on the STNG bus.

To be honest I would not say that the AIS-6 AIS functionality runs at two different baud rates. It provides AIS at 38.4Kb. (<- that's a full stop.) It has other non-AIS functionality that runs at 4.8Kb. So Actisense still haven't heard of an AIS that runs at two baud rates.

So far not in any direction. The NMEA2000 led lights up to show it is seeing the network but no data has come through so far.

I don't follow the data loop idea. If this happens how could any system not be affected by it? What will happen, and how can I prevent/avoid it?

 

[lpdsn]

So far not in any direction. The NMEA2000 led lights up to show it is seeing the network but no data has come through so far.

OK, IIRC the NMEA2K LEDs will only light when it is transmitting so it should be sending something out onto the STNG bus. How are you trying to display the AIS data? i70? Raymarine Chartplotter.

Worth checking the wiring from the AIS-6 to the Actisense. AIS-6 NMEA+ Output (blue) to Actisense NMEA+ input. NMEA output - (white) to Atisense NMEA- in. If it were me I'd not connect the others until I got the first route working.

I don't follow the data loop idea. If this happens how could any system not be affected by it? What will happen, and how can I prevent/avoid it?

It's an easy mistake to make when designing your instrument network but it is not a generic issue.

Anyway, easy to explain. Imagine you have Wind data on the STNG network (which from your description I assume you do). You send the Wind data through the Actisense to NMEA0183 and into the AIS-6. It multiplexes it with the AIS output and sends it back to the Actisense, which now sends it onto the STNG bus.

You now have two sources of wind data on the STNG bus. The original and the data echoed back via the data loop.

 

[Old Bumbulum]

Oh dear! Firstly, what's the result of a data loop and secondly is there anything I can do to prevent it? Or are we saying that my 2 way instrument plan is not workable because of it?

 

[RichardS]

Oh dear! Firstly, what's the result of a data loop and secondly is there anything I can do to prevent it? Or are we saying that my 2 way instrument plan is not workable because of it?

The result of a data loop on my Raymarine system is that waypoints on the screen plotter start behaving weirdly and moving around with the boat instead of staying where I put them. A red "N" also appears at the side of the waypoint which I think is the chartplotter's way of telling me that there is something amiss with the Nmea data.

It doesn't do any harm having a loop but you will soon know if you have got one.

Richard

 

[lpdsn]

Oh dear! Firstly, what's the result of a data loop and secondly is there anything I can do to prevent it? Or are we saying that my 2 way instrument plan is not workable because of it?

It basically means you have a second source of data on the STNG bus that lags a little behind the original. It can vary as to what that means. For example I accidentally caused my Ev-1 (Raymarine compass plus some) to stop sending heading data because it thought there was another compass on the network (was actually empty sentences originating on old Stowe kit that I didn't mean to route onto the N2K network).

In general, many pieces of kit allow you to select the source to use for particular categories of data on the network, so it might be possible to deal with the data loop, but no guarantees.

Anyway, first things first, have you got the AIS traffic working yet?