A25 NMEA / Instrument Wiring Diagram

[Jumpy07]

Thought this might be useful to some..

[mhanna]

From you picture you are using a Raymarine chart plotter and autopilot. I have something similar with the way the NEMA wiring is done for non Raymarine gear. But for the Ray stuff I ended up using their "seatalk" protocol, I forget exactly why but there were some features I gained by having the autopilot connected this way instead (with there newest software you can do some controlling of the autopilot via the chartplotter too). I have the Ray GPS module attached directly to the plotter too, then take the NEMA from there. I was going to go straight NEMA from the GPS dome, this way if the chartplotter died I could still have LAT/LONG info for other devices but again there was a reason to go straight seatalk...
I also have a NEMA "drop" (rs232 cable) in the cabin for laptop connections, I hooked up the TX back to the RX of the chart plotter. This way I do all of my planning of waypoints and routes via the PC and then push them up to the plotter. It is much easier to do rather than standing in front of the plotter.

I should put a diagram together myself, because when the time comes to work on something you hate draw it out while fixing....

Matt

[Mariner]

Sea-talk is a multi function, bi-directional communication system. NMEA 0183 is a one-way, single function sytstem. Using Sea-talk, you can share many different sets of data between multiple instruments, such as depth, speed, wind speed, wind direction, GPS position, etc... Using NMEA only allows you to take the information from one instrument and feed it to another, such as providing your GPS position to the VHF radio so that it can be broadcast at the touch of a button in an emergency. Most devices only have one NMEA in put and one NMEA output. For example, if you have a multi-function chartplotter display, using only NMEA wiring, you would be able to feed the GPS position from your GPS receiver to the display, but would not then be able to also feed the depth or speed from your fishfinder into this display.

[mhanna]

I actually use NMEA in bi-directional mode. Its true in most cases devices shoot out NMEA signals to another who is just receiving it ( ie.. GPS position to DSC VHF) but it can do more than that if its wired right. NMEA is nothing more than old RS232 computer signaling. Remember the old days when your external dialup modem was connected to your PC via that "special" cable with gold pins on the end, that was ASYNC and it can talk both ways.
The reason I say "can" is there are few instances where someone may use it on a boat but in my case I have the laptop downstairs receiving Lat, Long from the GPS and updating my position on its mapping software. But when I need to I can push certain info back to the GPS (waypoints and routes).

Matt