Holux GM-270 User Manual - 2.2 Software Interface
6
2.1.3 LED & External Antenna
◆
LED
LED OFF
GM-270 CF GPS Receiver Switch Off.
LED ON
GM-270 CF GPS Receiver Signal Searching.
LED Flashing
GM-270 CF GPS Receiver Signal Position Fixed.
◆
External Antenna Connector (MCX)…..Optional
As using GM-270 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 GPS-270 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 GPS-270PS 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
MSL Altitude
9.0
Meters
Units M
Meters
Geoid Separation
Meters