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Micro-JLT GNSS™ User Manual
16 © 2019 Jackson Labs Technologies, Inc.
recognized by Micro-JLT GNSS™ since the serial interface transmit and receive lines are completely
independent and orthogonal of one another.
The GSV and GSA messages include the satellites being tracked or included in the solution and both
messages use a modified satellite numbering scheme as detailed in the table below that makes all
satellite numbers unique. Also, to indicate the GNSS systems enabled and used to generate the
NMEA data, the Micro-JLT GNSS™ GNSDO’s NMEA output includes a two character talker ID
before the GGA, VTG, GLL, RMC, GSA, GSV, and ZDA sentence headers.
Table 3.1 shows the
talker IDs for the supported GNSS systems.
If more than one GNSS system is enabled, the talker ID of NMEA output is GN except for GSV
sentence which outputs multiple sets of sentences for each main talker ID. Refer to Section
3.3.10 for
example GSV output format. Also, the GSV output uses a modified satellite numbering scheme as
detailed in
Table 3.1 to allow all satellites in different GNSS systems to be differentiated.
In addition to standard NMEA sentences, the Micro-JLT GNSS™ GNSDO also supports PJLTS and
PJLTV Jackson Labs proprietary NMEA sentences, PASHR and a proprietary version of the GGA
sentence (GGASTat) described in Section
3.3.6 .
Please note that the position, direction, and speed data is delayed by one second from when the
GNSS receiver internally reported these to the Micro-JLT GNSS™ Microprocessor, so the position is
valid for the 1PPS signal previous to the last 1PPS signal at the time the data is sent (one second
delay). The time and date are properly output with correct UTC synchronization to the 1PPS signal
immediately prior to the data being sent.
Once set, the following command settings will be stored in NV memory, and generate selected
NMEA sentence output information even after power to the unit has been cycled.
3.3.5 GPS:GPGGA <int> [0,255]
This command instructs the Micro-JLT GNSS™ to send the NMEA standard GGA message every N
seconds, with N in the interval [0,255]. The command is disabled until the GNSS receiver achieves a
first fix.
This command has the following format:
GPS:GPGGA <int> [0,255]
The GPGGA string has the following data format:
Table 3.1 PRN numbering scheme for GNSS systems
GNSS Type SV Range GPGSV PRN vehicle
numbering Talker ID
GPS G1-G32 1-32 GP
SBAS S120-S158 33-64, 152-158 GP
Galileo E1-E36 301-336 GA
BeiDou B1-B37 401-437 GB
IMES I1-I10 173-182 GP
QZSS Q1-Q5 193-197 GP
GLONASS R1-R32, R? 65-96, 0 GL