Operation Manual

5
2.1.3 LED & External Antenna
◆ LED
LED OFF GR-271 CF GPS Receiver Switch Off.
LED ON GR-271 CF GPS Receiver Signal Searching.
LED Flashing GR-271 CF GPS Receiver Signal Position Fixed.
◆ External Antenna Connector (MCX)…..Optional
As using GR-271 CF GPS Receiver in a RV car, truck or bus, it might receive poor
signals through limited view to the sky. Replace the foldable antenna with the active one to
get better satellite signals. Windshields with heavy tinted or likewise may interfere with
signal receiving. An active antenna then becomes essential.
2.2 Software Interface
The GR-271 interface protocol is based on the National Marine Electronics Association's NMEA 0183 ASCII
interface specification, which is defined in NMEA 0183, Version 2.2 and the Radio Technical Commission for Maritime
Services (RTCM Recommended Standards For Differential Navstar GPS Service, Version 2.1, RTCM Special Committee
No.104).
2.2.1 NMEA Transmitted Messages
The GR-271PS supported by SiRF Technology Inc. also outputs data in NMEA-0183 format as defined by the
National Marine Electronics Association (NMEA), Standard.
The default communication parameters for NMEA output are 4800 baud, 8 data bits, stop bit, and no parity.
Table 2-1 NMEA-0183 Output Messages
NMEA Record Description
GGA Global positioning system fixed data
GSA GNSS DOP and active satellites
GSV GNSS satellites in view
RMC Recommended minimum specific GNSS data
•2.2.1.1 Global Positioning System Fix Data (GGA)
Table 2-2 contains the values for the following example:
$GPGGA,161229.487,3723.2475,N,12158.3416,W,1,07,1.0,9.0,M, , , ,0000*18
Table 2-2 GGA Data Format
Name Example Units Description
Message ID $GPGGA GGA protocol header
UTC Time 161229.487 hhmmss.sss
Latitude 3723.2475 ddmm.mmmm
N/S Indicator N N=north or S=south
Longitude 12158.3416 dddmm.mmmm
E/W Indicator W E=east or W=west
Position Fix Indicator 1 See Table 2-3
Satellites Used 07 Range 0 to 12
HDOP 1.0 Horizontal Dilution of Precision