Hi Russ:

I think you've got it right.  I don't have any hands-on experience with
the Cap'n program.  Usually we just use a switch to alternate between
the fluxgate and the GPS NMEA signals or with VNS you can have
alternative serial ports feeding NMEA data into the computer and switch
with the software.  Assumes you have additional serial ports which is
usually not the case.

I assume you want your compass as a fallback?  The Noland will multiplex
up to 4 separate talkers but you still have to have the listeners able
to differentiate between the talkers.

They have a website at www.nolandengineering.com

I have also heard that the Noland multiplexer can cause RF interference
if placed too close to certain electronic instruments but we have not
experienced this ourselves.

Incidentally, the NMEA 2000 standard is getting close to release.  This
is essentially a multiplexed protocol so a single coax will carry
multiple information streams which will make much more sense.  Of
course, the manufacturers have to all sign off on this and then actually
start to make equipment that supports this standard so I would guess, IF
it flies at all, we're looking at 3 years or so to seeing a full
compliment of equipment that supports the standard on the shelves.

Joe Engel
President
Marine Computer Services, Inc.
216 N. Tillamook St.
Portland, OR  97227
PHN: 503-281-3291
FAX: 503-288-3087
email: joe@jre.com

-----Original Message-----
From: russ@traceability.com [mailto:russ@traceability.com]
Sent: Monday, October 12, 1998 8:45 PM
To: trawler-world-list@samurai.com
Subject: Re: DGPS

Nothing specific. Just wondering if it works ok. I want to get the flux
gate compass into the Cap'n program, and i am already squirting DGPS in
through the only available port, so some multiplexing is in order. I was
thinking about designing one, but won't if this one, or something else,
works. You have talked about a bus for NMEA 0183, but as I read the
spec, it only allows one talker at a time unless you chain them through
a mux, and separate talker and listener channels, so it won't support a
true bus configuration. Am I wrong?
Thanks in advance for any info.

Joe Engel wrote:

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--
|----------------------------------------------------------------------|
|    Russ and Donna Sherwin                            |
|      "Four Seasons"                                        |
|    1981 Marine Trader DC44                            |
|    Sunnyvale, Ca 94087                                  |
|----------------------------------------------------------------------|

Hi joe:
Thanks for the input. Actually, Cap'n will display compass as well as
DGPS and a bunch of other stuff. I'd like to have magnetic boat heading
in addition to DGPS, which only calculates the heading based on where
you've been. The NMEA sentence headers will differentiate the various
data streams, presumably.
Russ
Joe Engel wrote:

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|----------------------------------------------------------------------|
|    Russ and Donna Sherwin                                            |
|      "Four Seasons"                                                  |
|    1981 Marine Trader DC44                                          |
|    Sunnyvale, Ca 94087                                              |
|----------------------------------------------------------------------|