wrote in message
...
On Fri, 1 Sep 2006 19:07:49 +0200, "Meindert Sprang"
wrote:

Well, let's define one!
It would be interesting though to see how the major brands transfer NMEA
over ethernet. But indeen, UDP is the best way since it is also a
connectionless/broadcast protocol just like NMEA0183 and NMEA2000.

Agreed. I use UDP in my stuff. It makes it easy to keep the network
"open" in that any device on the subnet can grab the data and use it.
For that reason, I just send the NMEA sentences one at a time, with no
mods or higher level constructs that a listener would have to be aware
of. The only "gotcha" (and it's irrelevant to the vast majority of
uses) is that all the routers I've looked at block UDP broadcasts from
going off the subnet, for good and sufficient reasons. If you want to
broadcast to another subnet you have to target the UDP to a specific
address on that subnet and let it repeat the message as a broadcast on
that subnet. At least, that's the way I solved the problem in my
stuff.

Unfortunately, I've found that most of the potential listeners to the
NMEA data I'm making available are so busy making everything
proprietary that this is less of a benefit than I hoped.


This thread has drifted in a direction that I like a lot. Since my original
AIS-specific question has likely been answered, I believe that the NMEA /
WiFi / BT topic deserves its own thread so it doesn't get lost. Of course I
still look forward to further AIS discussions.

I agree that WiFi and wired ethernet are the direction to go if you want to
build an open nav-electronics system (and I certainly do). BT is probably
better for the extremely power-sensitive applications, such as handhelds and
of course cellphone earphones. Meindert, I would definitely be a customer
for a wired ethernet mux. Of course, I've just got one boat, so I would
only buy one or two muxes.

I remain vigilant when it comes to power drain on my boat. I have three
100W solar panels on board, but depending on the cloud cover, and my point
of sail relative to the sun, I need to run the engine to charge batteries
for about an hour a day -- more if I am using the B&G hydraulic autopilot.
At anchor, the panels essentially keep up with the lower power drain. This
is why I am avoiding running a laptop full-time, and worry about the power
requirements of the electronics.

Of course if I shut off all the junk and just sail, I only have to power the
tricolor and compass light. But I do like my toys (and cold drinks).

-Paul