Jackson Labs FireFly-1A GPSDO, User Manual

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FireFly-1A User Manual
8 © 2011 Jackson Labs Technologies, Inc.
The GPS subsystem regroups all the commands related to the control and status of the GPS receiver.
The list of the commands supported is the following :
GPS:SATellite:TRAcking:COUNt?
GPS:SATellite:VISible:COUNt?
GPS:GPGGA <int> [0,255]
GPS:GGASTat <int> [0,255]
GPS:GPRMC <int> [0,255]
GPS:XYZSPeed <int> [0,255]
GPS:POSition?
GPS:RESET ONCE
GPS
3.3.1 GPS:SATellite
This group of commands describe the satellite constellation.
3.3.2 GPS:SATellite:TRAcking:COUNt?
This query returns the number of satellites being tracked.
3.3.3 GPS:SATellite:VISible:COUNt?
This query returns the number of satellites (PRN) that the almanac predicts should be visible, given
date, time, and position.
3.3.4 NMEA Support
The following two commands allow the FireFly-1A GPSDO to be used as an industry standard
navigation GPS receiver. The GPGGA and GPRMC NMEA commands comprise all necessary
information about the antenna position, height, velocity, direction, satellite info, fix info, time, date
and other information that can be used by standard navigation applications via the FireFly-1A
RS-232 interface.
Once enabled, FireFly-1A will send out information on the RS-232 transmit pin automatically every
N seconds. All incoming RS-232 commands are still recognized by FireFly-1A since the RS-232
interface transmit and receive lines are completely independent of one another.
Please note that the position, direction, and speed data is delayed by one second from when the GPS
receiver internally reported these to the FireFly-1A Microprocessor, so the position is valid for the
1PPS pulse previous to the last 1PPS pulse at the time the data is sent (one second delay). The time
and date are properly output with correct UTC synchronization to the 1PPS pulse immediately prior
to the data being sent.