C T C B S
Today, there are many gadgets available with GPS technology. GPS stands for ‘global positioning system.’ It provides the data corresponding to the position of the GPS receiver itself on international-standard latitude-longitude basis, in addition to the standard coordinated universal time (UTC), along with some more information received from the nearest satellite assigned for this purpose. (UTC is the primary time standard by which the world regulates clocks and time.)
Presented here is a PC-based GPS UHFHLYHU WhDW OHWV yRX finG WhH ORFDWLRn of a place and also gives the standard time on your PC. It may be useful in remote areas where no other wireless network for mobile and the Internet is available. The GPS receiver is also useful for research and other sophisticated applications.
Circuit description
The system consists of a PC, a GPS receiver that collects data from the satellite and an interfacing circuit to send the data to the PC through the serial port.
The only circuitry involved is the serial connection between the PC and the GPS module. The block diagram of the PC-based GPS receiver is shown in Fig. 1. All you need is a serial cable, a MAu2P2 driver circuit and power supply. The complete circuit is shown in Fig. 2. The system requires 5V as well as P.PV DC supplies—5V for the MAu2P2 and P.PV for the GPS module. GPS module. We have used the iWave GPS module (refer Fig. P) with external antenna. This module requires P.PV DC supply.
The basic working of the system is based upon decoding of the NMEA protocol. The iWave GPS module uses the NMEA-018P, which is a subset of the NMEA protocol. This protocol includes a set of messages which use $6C,, FhDUDFWHU VHW DnG hDYH D GHfinHG format. These messages are continuously sent by the GPS module to the interfacing device. Each message starts with a ‘A’ (hex 0x24) and ends with <CR><LF> (hex 0x0D 0x0A).
These messages include GGA, GGL, GSA, GSV, RMC, VTG and wDA. Here you need not know about all of these messages. vou need only the GGA message string which represents WhH WLPH, SRVLWLRn DnG fixHG GDWD IRU this application. This string has a format like:
AGPGGA, 00215P.000, PP42.6618, N, 11751.P858, W, 1.2, 27.0, M, -P4.2, M,, 0000*5E ZhHUH HDFh fiHOG VHSDUDWHG Ey FRPPD (,) represents a particular information. We have used only five of WhHVH fiHOGV IRU our purpose of displaying the time, latitude, latitude-direction, longitude and longitudedirection,
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