That sounds pretty darn interesting
One point I am missing - so you have a 38K output from DSC/AIS and 4.8K output from Seatalk/NMEA. How do you put both those outputs onto a single bluetooth converter?
This gets to the part I'm not as sure about - I'll need to try it out. It depends on whether Seatalk echos or passes through NMEA sentences that it receives [EDIT: Seatalk Technical Reference says it does pass through NMEA sentences]
. If so, it should work. My first try would be to feed the GPS sentences that come from the Bluetooth converter into Seatalk (using baud converter and Seatalk converter in series). Hopefully the Autopilot uses the GPS sentences that it gets from Seatalk, depth sounder adds its info onto the Seatalk chain, and the Seatalk converter then spits it all back out into the GX2150 input. The GX2150 uses the GPS coordinates for its DSC and for prioritizing the AIS readings, and spits out the DSC, AIS, and depth info to the Bluetooth converter, and it all makes its way to the chart plotter. [EDIT: Unfortunately this will not work as I described here. NMEA devices will receive sentences in and transmit their own sentences out, but they do not generally pass through the sentences that they receive. So I would need a multiplexer to do this.]
This is all a lot easier to follow in a schematic.
It's been a long time since I did serial interfacing, so I'll have to try it and see if it works. That's part of the reason I want to do it on the cheap, so I don't get stuck with a lot of expensive gear if I don't like it.
The other thing that I know will stir up a lot of controversy here is I plan to buy a RAM mount to put my Netbook in the cockpit. I'm a fair-weather daysailor, and did not get a drop of water in the cockpit last year. My Netbook is sitting virtually unused and has a matte finish screen that is incredibly bright - can see it easily in full daylight. And OpenCPN does a really nice display of AIS data. So I'll keep using my Garmin handheld as my primary device, but will have a bigger, brighter screen with AIS data on the Netbook. If it rains or starts splashing, I'll move the Netbook down to the cabin (Bluetooth will be nice for that) and just use the handheld in the cockpit like I did all last year.