Interfacing GPS with Atmega8

This article help you to interface GPS receiver with the AVR microcontroller. The GPS data's are displayed over an 16x2 LCD display. The program is written in Bascom Basic.

Program

'Project: M8 + GPS Module Decoder Test

'Results: M8 successful operation of a small board, display latitude and longitude and time

'Compiler version: bascom-avr 1.11.7.8

'avrprojects.info

'-------- Compiler directives statement ---------------------------

$ regfile = "M8def.dat"

$ crystal = 3686400

$ baud = 4800 'by the GPS module output baud rate

'------------- LCD connection, key definitions ------------------------------- ---------

Config Lcdpin = Pin, Db4 = Portd.4, Db5 = Portd.5, Db6 = Portd.6, Db7 = Portd.7, E = Portd.3, Rs = Portd.2

Config Lcd = 16 * 2

Config Pinc.3 = Input 'defined PortB.1 as input control terminal P

Portc.3 = 1'Portc .1 pull-up resistor and effective for the "1"

'------------ Variables and constants are defined in --------------------------------- ------

Dim Ews As String * 16, Nss As String * 11, Km As String * 5 'definition of longitude, latitude, speed,

Dim Hh As String * 2, Mm As String * 2, Ss As String * 2 'definition of hours, minutes, seconds

Dim Ns As String * 1, Ew As String * 1, Dw As String * 1 'definition of latitude north and south signs, things longitude signs, whether the location

Dim Przecinek As Byte, P As Byte

Dim Run As Byte, Gprmc As Byte, Cntr As Byte, Tudr As Byte, Ok As Bit

Run = 1: Reset Ok

P = 1

'-------------- Defined and open the serial port interrupt subroutine interrupt --------------------------- --------------

On Urxc Uart_rx

Enable Urxc

Enable Interrupts

Initial'--------------- program interface ------------------------------ --------------

Cls

Cursor Off

Locate 1, 4

Lcd "GPS Viewer"

Lowerline

Lcd "avrprojects.info"

Wait 1

'----------------- The main program display interface -----------------

Do

While Ok = 0: Wend

Reset Ok

If Pinc.3 = 0 Then 'Pinb.1 grounding also open up

'Switch to display the page

Do

Loop Until Pinc.3 = 1

Incr P

If P> 2 Then

P = 1

End If

End If

Select Case P

'- P1

Case 1

Cls

Cursor Off

Locate 1, 1

Lcd Ns: Lcd "": Lcd Nss' first line to display latitude

Locate 1, 16

Lcd Dw 'location mark

Ews = Ews + "" + Km

Locate 2, 1 'second line shows the longitude

Lcd Ew: Lcd Ews' and speed of

'- P2

Case 2

Cls

Cursor Off

Locate 1, 1

Lcd "UTC": Lcd Hh: Lcd ":": Lcd Mm: Lcd ":": Lcd Ss' first line of the display UTC time

'Locate 2, 1

'Lcd "20": Lcd Ye: Lcd "-": Lcd Mo: Lcd "-": Lcd Da' second line shows the date, but there are problems

'Lcd Da

End Select

Loop

End

'---------------------- Serial port interrupt reception subroutine ---------------------- ------

Uart_rx:

If Run <> 0 Then

Run = Udr Xor 36

If Run = 0 Then

Cntr = 0

Nss = ""

Ews = ""

Km = ""

Ns = ""

Ew = ""

Dw = ""

               '2

Hh = ""

Mm = ""

Ss = ""

End If

Else

Select Case Cntr

Case 0 To 4

Tudr = Lookup (cntr, Rmc) 'to determine whether the received characters include "GPRMC"

Run = Udr Xor Tudr

Case 6 To 7

Hh = Hh + Chr (udr) 'UTC Time: "time"

Case 8 To 9

Mm = Mm + Chr (udr) 'UTC Time: "Separation"

Case 10 To 11

Ss = Ss + Chr (udr) 'UTC Time: "seconds"

Case 13

Dw = Dw + Chr (udr) 'whether the location mark

Case 15 To 22

Nss = Nss + Chr (udr) 'latitude

Case 24

Ns = Ns + Chr (udr) 'North latitude flag

Case 26 To 34

Ews = Ews + Chr (udr) 'longitude

Case 36

Ew = Ew + Chr (udr) 'stuff longitude flag

Case 38 To 42

Km = Km + Chr (udr) 'speed, unit section, a = 1852M / H, is not converted into kilometers

Case 50

Set Ok: Run = 1

Case Else

Tudr = Udr

End Select

Incr Cntr

End If

Return

'GPS statement, the head of ASCII code

Gga:

Data 71, 80, 71, 71, 65 'GPGGA

Vtg:

Data 71, 80, 86, 84, 71 'GPVTG

Rmc:

Data 71, 80, 82, 77, 67 'GPRMC