GPS vendors; this is the line that supplies the NMEA sentences to your
TNC.
Some GPS units may allow for programming of parameters. If so, this is accom
-
plished by passing commands to the GPS unit from a terminal (or TNC) via an
additional pin in the data port.
If your GPS unit accepts the setting of parameters, you may wish to connect the
third wire of your cable from the input data pin of the GPS data port to pin 3 of
the TNC serial port. Again, consult your GPS manual for the name of this pin;
names vary by vendor. Also, make sure this pin will accept an RS-232 signal
(+ and - voltages).
Setup: Configuring a Kantronics TNC for GPS Operation
To configure your Kantronics TNC in GPS Mode you must set several command
parameters from your PC keyboard as follows:
• select the GPS strings you will be capturing in each of the Location Text
buffers
• set the beacon rates for each Location Text buffer you are using
• enter the unproto paths for each Location Text buffer you are using
You determine which GPS strings will be stored in the Location Text (LT) buffers
by entering the string header with the GPSHEAD command. The TNC searches
for specific strings of data from the GPS unit and stores them in up to four LT
buffers. These LT buffers may then be transmitted at periodic intervals as a bea
-
con. The frequency of the beacons is controlled independently for each LT buffer,
by the BLT command (which stands for Beacon Location Text). You may also set
the destination address and the path for each of the four LT beacons independ
-
ently using the Location Text Path (LTP) command.
+
If the GPSHEAD string for any LT buffer is empty, that LT buffer can be set up
an an auxilary beacon; LT, BLT, and LTP are used like BTEXT, BEACON, and
UNPROTO.
Packet Modes of Operation GPS NMEA Interfacing Capability
User’s Guide 182 KAM’98 v 8.3
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