BoatBanter.com - HELP: Connecting PC To Raynav 300

"claus" wrote in
:

I am trying to connect my PC to a RayNav 300 using the NMEA input to
the Raynav.

The Raynav connector has 4 separate wires:

WHITE (+ve)
GREEN (-ve)
YELLOW (Data Out)
BROWN (Common)

Based on an (un) educated guess, I presume that I connect the WHITE
wire to pin 3 (transmit) on the PC's serial connector and the GREEN
wire to pin 5 (ground)...but perhaps that is wrong???

(I am using the Yellow and Brown wires to receive NMEA from the GPS -
and that works perfectly.)

I can't find any documentation on this at the Raymarine.

Any advise will be appreciated. Larry???

claus

From the notations, I'd say the data in is a balanced line, as NMEA is
supposed to be with + and - out-of-phase signals to reduce noise. You
should be able to ground Green to Brown, the ground on the PC, then hook
White to pin 3 and send data to the Raynav.

Be informed the levels between RS-232C (+12V and -12V, for 1 and 0) are
all wrong for RS-422 we call (or curse?) as NMEA. But the two systems
will normally respond to each other's missive voltages quite well at
lower baud rates.

Is this the ONLY connection to this NMEA port? Remember...stupid NMEA
can only have ONE talker on a circuit to a bunch of listeners. You can't
hook two talkers to the same wires, like you can SeaTalk, because NMEA
(RS-422) was never designed to be a multitalker comm system, which makes
Meindert smile all the way to the bank selling his multiplexers to make
it possible. If the computer is the only thing hooked to White/Green it
should be fine. Try it. The ports all have protective resistors....

Larry
--
Halloween candy left over.....
Is there a downside?