NMEA to SeaTalk

[Mike Smith]

I spent the afternoon on Breezer doing a dockside calibration all of my Raymarine instruments.  It's amazing what you can learn just punching buttons and making notes, and of course, reading the manuals!  This is my setup: I have a Garmin GPS speaking NMEA to my ST4000+ autopilot, so I have all the data required for GPS piloting - especially SOG via the GPS display.  The autopilot converses via the SeaTalk bus with the ST60 depthmeter, wind indicator, and knotmeter.  However, when in calibration mode, I tried to select SOG on the knotmeter, the display reads all dashes (- - -), which according to the manual, indicates that the knotmeter is not receiving appropriate input data.  Since I'm stationary, it should read 0.0)  My assumption is, that once the autopilot receives NMEA SOG data from the GPS, it converts it to SeaTalk format and forwards it to the knotmeter for display, but this doesn't seem to be the case.  Does anyone have a similar configuration of instruments and, if so, have you been able to capture GPS SOG for display on the ST60 knotmeter?  I have searched both this website and Raymarine's without success.

Mike

[DEMERY]

Mike,

I have the same configuration. A Raymarine GPS/Chart Plotter that is connected to my 4000+ Auto Pilot via NMEA. The autopilot is connected to both a ST60 Depth and ST60 Speed instruments via Sea Talk. I have SOG on my ST60 Speed Instrument as well as additional GPS data being repeated on my 4000+ Autopilot. I know I didn't answer your specific question, but I wanted to let you know that your configuration should work.

Good Luck,

Dave

[Mike Smith]

Thanks, Dave -

Only difference is my GPS is a Garmin with a NMEA output to the ST4000+.  Hopefully I can get out toward the end of the week to check it out.

Thanks again,
Mike

[rirvine]

A potential problem could be the result of NMEA sentences are only "semi-standard" across vendors. Once they disappear into Raymarine boxes the situation gets even less clear as to what might come out on the Seatalk.

Raymarine boxes will only convert data from NMEA to Seatalk that arrive in specific NMEA sentences and not all Raymarine boxes act the same.  From the ST-4000, these are listed in the NMEA section of the manual.  So the question is:  Does the Garmin send the SOG in a sentence that Raymarine will convert and send out on Seatalk?   The fact that a Raymarine box will displays a piece of data does no mean they will send it out on Seatalk.

As Google of NMEA could turn up some helpful information.  The best definition of NMEA sentences that I have been able to find is:

http://www.nmea.de/nmea0183datensaetze.html

Hope this helps.

[David Sanner]

Another option is getting a NMEA multiplexer with a Seatalk option.
It looks like these boxes have a lot more options / control / filtering than the RayMarine box.
http://brookhouseonline.com/nmea_multiplexer.htm
(This is also helps if you have a DSC radio and/or an AIS box)

Good NMEA link Ray.  I was just reading this last night:  http://www.gpsinformation.org/dale/nmea.htm
Apparently some garmin units send NMEA version 2.3 ... (there's a NMEA 3.0 version).

On a side note:
I'm looking for a more permanently wired GPS solution than my Garmin etrex Vista.  (see photo)
(Small charts at the helm, sending GPS data to a full chart plotter on a laptop at the nav table)

The $75 Garmin 'hockey puck' , GPS 18 PC, is a nice option but unlike my etrex Vista there isn't a flux
compass and can only give heading based on COG.    But considering a Garmin Vista with WAAS is under
$200 and you can also load maps onto it it's hard to find a better option that also has a flux compass.


I guess I could get a brookhouse multiplexer and try to read my ST4000 flux compass
heading info but they cost about as much as an etrex Vista.... and likely another
set of headaches though maybe I could finally get wind info to my ST4000.

Maybe there's isn't a cheap solution besides a handheld that provides both heading
and GPS info... or just go with the $75 GPS 18 as a backup.  I'm getting so used to
having a GPS onboard I better have a backup!

[Craig Illman]

David -

Where did you get that little clamp-on piece that you have your eTrex mounted on? I have mine at the top of the pedestal guard, but I really like your setup better!

- Craig

[David Sanner]

That's a recent upgrade...  straight forward... take a 1" diameter piece of stainless and drill it off
(instead of cutting it off) with a  one inch bit leaving a piece about 2" long total.
Then make two small cuts in it for a hose clamp to slip in... works well.

I haven't figured out if having my GPS flux gate compass is effected buy it's
proximity to all the metal.  I think it's workable.