Attaching a GPS to the Palm handheld

Beginning with version 1.10 of GL, the program has the ability to
read the current position or time from a GPS receiver.  The receiver 
must be set to provide NMEA data at 4800 baud on a serial connection.

For this feature, a cable or cables is required that make the serial
connection between the GPS and the handheld.  This document will 
describe the method that was used to connect a Garmin GPS II+ to a
Palm IIIxe and an original Palm Pilot.  Similar methods should work
for other devices, but it is up to the user to adapt this information.

This document will refer to a several image files which should be
found in the doc directory.

The connectors that are used for these connections are shown in
these image files:
    palmcon.gif
    dbconns.gif
    GarminOut.gif

Several years ago I made a cable to connect my Garmin GPS to a PC
for running map software.  The connector which plugs into the PC
serial connector must be a DB-9 Female.  The image GarminCable.gif
shows the cable I made up to do that.  I normally connect the
external power connection to 12V from my car.

The image cableser.gif shows the wiring for a standard Palm HotSync
cable.  This cable has the Palm connector for the base of the handheld
on one end and a DB-9 F connector on the other for plugging into a PC
serial port.

The Garmin and HotSync cables can't be plugged together directly since 
they both have DB-9 F connectors.  One option is to connect them with 
a DB-9 Null Modem adapter (and possibly a M-M DB-9 adapter).  This will 
work.

The approach I chose was to keep my existing Garmin cable, which works
with the PC, and modify a Palm cable to connect with this.  On the
hotsync cable, I cut off the DB-9 F connector and replaced it with a
DB-9 M connector.  The image cablegps.gif shows the wiring for this
cable.  This modified cable can be plugged into the existing Garmin
cable.

There is another option that I haven't tried yet, but should allow 
using the GPS with both a PC and the Palm simultaneously.  To do this
the Garmin cable would be modified to add a new DB-9 M connector in
addition to the existing DB-9 F.  The Garmin T (Data Out)(brown) would 
also be connected to the new DB-9 M pin 3.  The Garmin Ground (-) 
(black) would be connected to pins 5 of both DB-9 connectors.  The
DB-9 F on the Garmin cable can be plugged into a PC, and the new DB-9 M
would plug into a standard Palm HotSync cable.
