"Pascal" wrote in message
ups.com...
Returning to my old subject, this weekend my friend had made the
software update for his C80 wich now is AIS Ready and we two now have
our respective SR161 AIS receivers working and running with the several
PC software (SeaClear, ShipPlotter, OziExplorer and SOB).

The problem which arises now is related to the availability of only one
NMEA port on the Raymarine C80 chart-plotter. I have not seen it (the
physical installation) but appears that this port already have one
connection that I think, it is the VHF/DSC connection, which is NMEA
IN for VHF and NMEA Out for C80.

The questions a

1) Supposing that the connection from the Gyro (which comes with the AP
Smart Pilot S1G) is made by Seatalk and not on the NMEA port, the NMEA
Out of C80 should be 4800 bps (GPS Out to VHF In) or must be 9600? I
heard anywhere some time ago that DSC mandates 9600... It is true?

DSC is standard NMEA and therefore 4800 bps.

2) Since the NMEA IN on the C80 (NMEA Out on the SR161) is 38400 bps,
this NMEA port on the C80 could work using NMEA IN at 38400 bps from
AIS and NMEA Out to VHF at 4800/9600 bps?

Cannot be. The one and only NMEA port cannot send and receive at different
speeds.

I cannot answer the remaining questions. But Raymarine made this whole thing
very fuzzy. For instance, in the manual it says you can also set the NMEA
port to a "9600 Navtex" mode. Apparently people think that Navtext is also
NMEA and want to connect their gyro, AIS and a navtex receiver to a
multplexer, which will not work. If that NMEA port is set to Navtex, it will
not receive NMEA.

To overcome the speed problem, we have come up with a MiniPlex-AIS, which
has three inputs at 4800 and one input at 38400. The RS-232 port of this mux
goes to the C/E display, set to 38400. Data sent from the C/E display to the
multiplexer at 38400 is output at a separate NMEA port running at 4800. I
still have to test whether the NMEA port of the C/E displays can be
connected to an RS-232 port. Again, the manuals are fuzzy about this: The
terminals are called ve+ and ve-(common). Which leads me to believe that the
ve- terminals are connected together because both have "common" in their
designation. But this would be stupid because it violates the NMEA standard.
I spoke to a few people involved in the development of the C/E displays at
Raymarine and even they couldn't tell me clearly how the NMEA port is
setup....
So if someone out there with a C/E display could get his multimeter and
measure the resistance between both ve-(common) terminals, I would be very
interested in the result.

If on the other hand the NMEA interface is completely isolated from the rest
of the system, it will be no problem to connect it to an RS-232 port.

Meindert