Garmin GPS 152 NMEA in/out

[Lomax]

I'm helping a friend rewire the instrumentation in his boat, and install an OpenCPN navigation computer. The instruments are rather old, but fully functional, so I see no need to spend £££ on replacing anything. He's got a Garmin GPS 152 navigator and a NavMan Multi 3100s log/depth-sounder with a repeater instrument. The log/depth-sounder sends depth and speed NMEA data to the Garmin GPS 152 (via NMEA in #2, or "COM2"), and this information displays correctly on its screen. The OpenCPN computer is connected to the GPS 152's NMEA "COM1" port, for both input and output, and receives GPS NMEA messages correctly. However, the NMEA output from the GPS 152 does not include the speed/depth messages it receives from the NavMan instrument. I was under the impression that the GPS 152 would repeat NMEA messages it receives from "COM2" input on "COM1" output, but despite digging around in the menus and the manual I haven't been able to find any option to enable this. I'm hoping someone here might have experience of the Garmin GPS 152, and is able to confirm whether the GPS 152 provides NMEA data repetition, and if so what needs to be done to make it work.

 

[PaulRainbow]

It only outpts GPBOD, GPBWC, GPGGA, GPGLL, GPGSA, GPGSV, GPRMB, GPRMC, GPRTE, GPVTG, GPWPL, and GPXTE; Proprietary sentences — PGRME, PGRMM, PGRMZ, and PSLIB

 

[Lomax]

Thanks. I take it those are all GPS sentences, and don't contain depth or speed through water?

 

[prv]

Correct.

Presumably, though, you can just use another serial port on the openCPN computer. That’s a more “correct” way to wire NMEA0183 anyway, rather than rely on one device repeating the other.

Pete

 

[GHA]

If its a dedicated on board nav computer then it really is well worth installing signalk to deal with the data side. Then you can get in to any non standard nmea sentences and do what you want with them. Or do anything you can think of

 

[prv]

How about waiting until there‘s a problem, before seeking a solution ?

Pete

 

[Lomax]

Of course a typical installation requires more than one serial port on the nav computer, due to the single talker nature of NMEA 0183, but in this particular case I hoped it would be possible to get away with just one for these two instruments. Certainly some instruments with multiple NMEA inputs do "repeat" the data on their output(s), and you can get dedicated NMEA multiplexer hardware that does the same job. I am also well aware of Kplex, and Signal K, but multiple RS-232 <> USB adapters cost money and take up space. On my own boat I have used a six port RS-232 to single USB box, with screw terminals rather than D-Sub 9 connectors, specifically to save precious space beneath the instrument panel, and to negate the need for a USB hub.

Below are before/after pics of what I ended up doing for my friend, I hope you'll all agree that it's a substantial improvement