Easiest way to get NMEA 0183 from Seatalk

[Tkeeth]

Originally Posted by SV Dawn

Tenedos,
I have a Raymarine E85001 Seatalk/NMEA Interface Box I'll sell. It was only installed for a couple of months and replaced with a Shipmodul Wi-Fi unit. Original packaging, manuals etc. PM me if interested. Andy

If he doesnt want it, i may

[barnakiel]

It was a Garmin problem, not a Ray box problem.

The box is OK. I have used it many times.

You can get a small Ray plotter to work as a box but this sure is some dollars out.

b.

[Tenedos]

Originally Posted by Tkeeth

I have close to the same system and am doing the same thing. At the autopilot i have a multifunctuon blah blah from raymarine. Open the cover and you see some terminals marked seatalk, on the ends there are a set for nmea 0183 in and out..

You are lucky. I went down the same path and opened the cover. ST4000 only has an NMEA 0183 in, and no out. It has an available Seatalk1 connector, which I guess is the only option to convert to NMEA or straight to USB/Serial, which is what I need anyways.

[smac999]

Originally Posted by tedowens

I tried to do this using an E85001 that I bought on ebay. It worked however, I ported the data into a Garmin chart plotter. Unfortunately, the Garmin would intermittently and spontaneously shut down. Some times this happened right away and sometimes, it would work well for 8 hours at a time. The Garmin technical support team blamed it on the Raymarine E85001 (although they could not specify what the root cause was). Since the E85001 was no longer in production and I bought it second hand, I could not get support from Raymarine. In the end, I gave up and learned to live without integrated instruments.

Sone garmin plotters have a gfi in the power supply. So if you have a ground loop or something on the nmea line draining current, they will shut off. according to garmin tech support after spending a lot of time trying to fix one. Would only shut off when nmea 183 device was connected. Had to put in a opto coupled expander in between so the plotter couldm't leak current

[philtrick]

There are a couple of options:
If you can do it yourself:
Simple DIY interface designs [MeshCMS]

He also sells a full Arduino board for taking seatalk / NMEA etc. into a raspberry pi

Also, there is this, with a distribution for the Pi which seems quite well featured:
Sailing with free hardware | Sailoog

[barnakiel]

Originally Posted by Tenedos

You are lucky. I went down the same path and opened the cover. ST4000 only has an NMEA 0183 in, and no out. It has an available Seatalk1 connector, which I guess is the only option to convert to NMEA or straight to USB/Serial, which is what I need anyways.

That there are connectors does not imply you can convert the signal. Some Ray pilots had ST input for rudder sensor. These did not translate.

The translation is done on a chip. When this chip is absent, ST and nmea data is processed but not translated.

Browse the web for an app. If there is an App that does what you want, you can wire your own bridge/mux with a cheapo smartphone or tablet. These consume only marginal power with the screen off.

Cheers,
b.

[muttnik]

Here's the options I thought of (including repletion of what others have said):
1. E85001. The most straightforward approach but these things are much sought after on eBay: Expect to pay $100 or more
2. Raymarine plotters which do seatalk 1 and NMEA-0183 should bridge data for you. I have my C90W bridging my seatalk data to the raspberry pi. But I'm guessing you don't have such a plotter and buying an old plotter to do the data bridging isn't cost, space, or power efficient.
3. Some of the old instruments will convert a subset of seatalk commands: The ST50+ multi for example. The subset of conversions they do may or may not be adequate for your needs. These instrument also seem to cost even more than the E85001 on eBay.

I don't know if Raymarine licensed seatalk to anyone else. I get the impression that non-Raymarine devices might have cribbed their data from Thomas Knauf's go-to seatalk site:
Thomas Knauf Â*Â*Â*Â*SeaTalk Technical Reference
Note that the seatalk->NMEA conversion is not one to one: sometimes you have to assemble an NMEA sentence from several seatalk words and maybe some people's algorithms for doing that (is this the long that goes with that lat or did I miss one?) are not the same as Raymarine's. It probably doesn't matter too much. I might be a bit concerned about how well non-Raymarine vendors did the collision management when writing nmea->seatalk. Doubtless many do just fine but I saw at least one open source arduino-based project where there didn't appear to be collision management at all.

but I digress...

There will be alternatives to the stuff below and I don't have personal experience of any of them other than exchanging a few emails
4. Frank Wallenwein has been selling converters for years: www.gadgetpool.de - Die Homepage. Various to choose from including little compact ones: Possibly the closest "new" alternative to the E85001. Not super cheap and not under $100 but not outrageous.

5. various people do nmea multiplexers which do seatalk conversion including brookhouse and shipmodul. vyacht has also been mentioned but these are "fatter" solutions than I believe the OP is really looking for

6. DIY.

You could do bit banging with a microcontroller. Or build a circuit to invert the signal and change it to something your UARTs are happy to deal with. The use of the 9th bit to flag command bytes is not such a big deal where you have access to the parity bit but it's slightly more challenging from Linux userspace if you don't want to stick a microcontroler between seatalk and the pi. You *can* do it though IF your serial device allows you to set mark and space parity (set space parity, parity error means the 9th bit is set) and it actually flags parity errors correctly (which a startech serial to usb converter I was using didn't). I did play around with some seatalk-reading code with this technique and the Thomas Knauf circuit which did work but you can't write the collision management in linux userspace so it would need to be read only. Note also that I understand there are better circuits around for doing seatalk to rs232 conversion than the one on Thomas Knauf's site but I don't have links and that one worked ok for me.

[conachair]

Has anyone here actually got an arduino to read seatalk and talk nmea?

[electronicmarin]

Originally Posted by muttnik

There will be alternatives to the stuff below and I don't have personal experience of any of them other than exchanging a few emails
4. Frank Wallenwein has been selling converters for years: www.gadgetpool.de - Die Homepage. Various to choose from including little compact ones: Possibly the closest "new" alternative to the E85001. Not super cheap and not under $100 but not outrageous.

You could do bit banging with a microcontroller. Or build a circuit to invert the signal and change it to something your UARTs are happy to deal with. The use of the 9th bit to flag command bytes is not such a big deal where you have access to the parity bit but it's slightly more challenging from Linux userspace if you don't want to stick a microcontroler between seatalk and the pi. You *can* do it though IF your serial device allows you to set mark and space parity (set space parity, parity error means the 9th bit is set) and it actually flags parity errors correctly (which a startech serial to usb converter I was using didn't). I did play around with some seatalk-reading code with this technique and the Thomas Knauf circuit which did work but you can't write the collision management in linux userspace so it would need to be read only. Note also that I understand there are better circuits around for doing seatalk to rs232 conversion than the one on Thomas Knauf's site but I don't have links and that one worked ok for me.

I've build myself a seatalk to nmea interface a while ago, after playing a couple of days with seatlk bitbang ecc I just email Frank from gadgetpool and he send me the project files, it worked right away and did not seem to have anny collision problems. I've chosed the smd path for the pcb and alredy installed couple of them in my friends boats and they are working ok... here's the video of the construction

https://www.youtube.com/watch?v=aMVJ-hoGb-g

and here's one of them working with a simrad:

https://www.youtube.com/watch?v=D4LU_MT5Y_o