How to interface GPS with PIC18F4550 Microcontroller

1.               A string always starts with a ‘$’ sign

2.               GPGGA : Global Positioning System Fix Data

3.                ‘,’ Comma indicates the separation between two values

4.               100156.000 : GMT time as 10(hr):01(min):56(sec):000(ms)

5.               2650.9416,N: Latitude 26(degree) 50(minutes) 9416(sec) North

6.               07547.8441,E: Longitude 075(degree) 47(minutes) 8441(sec) East

7.               1 : Fix Quantity 0= invalid data, 1= valid data, 2=DGPS fix

8.               08 :  Number of satellites currently viewed.

9.               1.0: HDOP

10.           442.8,M : Altitude (Height above sea level in meter)

11.            -42.5,M :         Geoids height

12.           __ , DGPS data

13.           0000 : DGPS data

14.           *71 : checksum

The main objective here is to find the location of the GPS Receiver in terms of latitude and longitude. The GPS module gives output data in RS232 logic level format. To convert the RS232 logic level into TTL, a line converter MAX232 has been connected between GPS module and PIC18F4550. (Also refer PIC USART) The circuit connection of GPS module with microcontroller is shown in the circuit diagram tab. The latitude and longitude data has been displayed on a 16×2 LCD interfaced to PIC.