Kantronics KPC-3 Plus - Page 171

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GPSPORT [baud] [NORMAL | INVERTED] [CHECKSUM | NOCHECK]
default 0 NORMAL CHECKSUM
This command allows for a second serial input port for a GPS unit, using a firmware
UART.
If ‗baud‘ is non-zero, the XCD pin in the radio port can be used as a GPS input during
regular operation of the KPC-3 Plus. ‗baud‘ may be set to 0, 300, 600, 1200, 2400, or
4800. If NORMAL is specified, the sense (polarity) of the XCD pin is RS232; the XCD
pin would be expecting RS232 input or 0-5 V input of the same polarity. If INVERTED is
specified, the XCD pin would be expecting polarity opposite of RS232. Most stand-alone
GPS units use RS232 or 0-5 V output of the same polarity. If CHECKSUM is specified,
the firmware will pass along only GPS sentences, which have valid checksums, and
also GPS sentences, which do not have a checksum. Not all GPS units will append
checksums to the GPS sentences that they send; some GPS sentences require a
checksum, while others do not.
If you wish to use the GPSPORT, note that the KPC-3 Plus cannot send any
initialization string to the GPS unit; you must pre-initialize the GPS unit before
connecting it up to the XCD pin.
Note: The GPSPORT is a firmware UART. Although the KPC-3 Plus was tested and
found to accept GPS data without error at 4800 bps while the KPC-3 Plus was idle,
errors occurred if the KPC-3 Plus was active sending and receiving packets and
communicating over the RS232 port. Tests found that few, if any, errors occurred when
‗baud‘ was set to 2400. For best results, set ‗baud‘ as low as possible for your
application; if you need to set ‗baud‘ to 4800, you should also use the CHECKSUM
parameter to discard errors.
Note: When GPSPORT is zero (0), the XCD pin reverts to its original function, inhibiting
PTT. If the INTFACE command is set to GPS, the TNC assumes that the GPS device is
attached to the normal RS232 port and not the secondary serial input. If INTFACE is set
to KISS, XKISS, GPS, or MODEM, you should set GPSPORT to zero.
GPSTIME { OFF | VALID | ON } { GGA | GLL | RMC | ZDA }
default VALID RMC
If GPSTIME is set to OFF, the TNC software clock is not set when NMEA strings are
received. If set to VALID, the clock is set but only if the valid bit in the string specified is
set. If set to ON, the time is acquired from the string specified.
Note:
In any event, any string must have a valid checksum.
Time is not updated if the time received in a string is the same as the last time
received.