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4 SOFTWARE INTERFACE
This section describes the details of the serial port commands through which the TISTAR25 is
controlled and monitored. The serial port commands allow users to set the receiver
parameters, configure output message type, and retrieve status information. The baud rate
and protocol of the host COM port must match the baud rate and protocol of the GPS receiver
serial port for commands and data to be successfully transmitted and received. The default
receiver protocol is 4800baud, 8 data bits, 1 stop bit, and none parity.
4.1 NMEA OUTPUT MESSAGE SPECIFICATION
The TISTAR25 supports NMEA-0183 output format as defined by the National Marine
Electronics Association (http://www.nmea.org)
. The currently supported NMEA messages for
GPS applications are:
GGA Global Positioning System Fix Data
GLL Geographic Position – Latitude / Longitude
GSA GNSS DOP and Active Satellites
GSV GNSS Satellites in View
RMC Recommended Minimum Specific GNSS Data
VTG Course Over Ground and Ground Speed
4.1.1 NMEA Checksum Calculation
The optional NMEA checksum can be enabled or disabled when setting up the NMEA protocol.
The checksum consists of a “*” and two hexadecimal digits derived by exclusive-OR of all the
characters between, but not including, the “$” and “*” characters.