[SOLVED] SIM908 GPS: how to extract the Longitude,Latitude

[jayanth.devarayanadurga]

Does your GPS send line break character at the end of each data transmission? If you GPS data frequency is 1 Hz that is emits data every 1 sec?

How do you get data with different formats everytime?


mikroC PRO AVR Code.

---

Code C - [expand]
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unsigned char gpsData[85], myData[18], processNMEA = 0;
unsigned int k = 0;
 
void extractData(){
 
     unsigned int i = 0, j = 0, gotData = 0;
 
     if(gpsData[1] == '0'){
     
          j = 0;
          
          do{
              while(gpsData[i] != ',')i++;
              ++i;
              ++gotData;
              j = 0;
 
              while(gpsData[i] != ','){
                    myData[j] = gpsData[i];
                    ++i;
                    ++j;
              }
 
              myData[j] = '\0';
              UART1_Write_Text(myData);
              UART1_Write(13);
              UART1_Write(10);
 
          }while(gotData < 8);
     }
}
 
void main() {
 
     DDRD = 0xFE;
     PORTD = 0x00;
     
     UART1_Init(57600);
     Delay_ms(2000);
 
 
     
     UART1_Write_Text("Paste some GPS data to Virtual Terminal\r\n\r\n");
     
     while(1){
 
              UART1_Read_Text(gpsData, "st", 85);
              k = strlen(gpsData);
              gpsData[k] = ',';
              k = 0;
              extractData();
 
     }
}

---

 

[jayanth.devarayanadurga]

Here is a version which use ISR. It has 2 methods, one using ISR and one using library.

 

[embRTS]

It's done but with a little errors

 

[jayanth.devarayanadurga]

What errors do you see in my code?

 

[embRTS]

Not in your code it's some fault in my code as i have separated it with new line so some errors came,anyways thanks Jayanth

- - - Updated - - -

7739.1581837
3
1258.0692791
5
811.9531868
1
20131213072750.1302
1
77
1
101

0.0000000
0
0.0000000
0

- - - Updated - - -

This '3' , '5' are coming which is not supposed to be

 

[jayanth.devarayanadurga]

Post your code. I will check.

 

[embRTS]

Ya Finally fixed it done but I think the code once running it's in the ISR only not coming out of this

as
at the end

the message "ends***********" should also get to be printed
but it's not like that

[CODE]
////////////////////////////////////////ISR////////
unsigned char index;
volatile unsigned char inData[80]= "";
///////////////////////////////////////////
ISR(USART1_RX_vect)
{
	inData[index] = UDR1;
	if(inData[0] == '0')
	index++;
}
/////////////////
/*Extract Data function*/
void extract_data()
{
	unsigned char mydata[18] = "";
	unsigned int  i=0,j=0 , gotdata = 0;
	_delay_ms(100);
	if(inData[0] == '0'){
		i=j=0;
		do
		{
			while(inData[i] != ',')i++;
			++i;
			++gotdata;
			j=0;
			
		while(inData[i] != ',')
		{
		mydata[j] = inData[i]; ++i ; ++j;
		}
		mydata[j] = '\0';
		_delay_ms(100);
sendstring_softuart(mydata);
_delay_ms(5);
sendstring_softuart("\r\n");

		
	} while (gotdata < 8);
	
	
}
///////////while(1) loop/////////////////////////
	while(1)
	{
		
		
		_delay_ms(3000);
		sendstring_softuart("start\r\n");
				_delay_ms(2000);
		sendstring_uart("AT+CGPSINF=0\r");  //AT Command to get GPS
		_delay_ms(500);

extract_data();  //To get and print gps data
	_delay_ms(15000);
	sendstring_softuart("end*********************END\r\n");
	
}

[/CODE]
and the output

start
7739.139568
1258.082222
851.041199
20131213104502.827
11
12
0.000000
0.000000
start
7739.146266
1258.068929
829.928833
20131213104540.650
8
12
0.000000
0.000000
start
7739.145327
1258.070563
831.828552
20131213104618.408
8
12
0.000000
0.000000

Is that in ISR onnly ??

 

[jayanth.devarayanadurga]

It is printing 8 values and it is correct.

 

[embRTS]

Ok , exactly it's correct but what about printing the last line "end*********" i mean why its not printed on the Serial Port ?

 

[jayanth.devarayanadurga]

Zip and post your project files. I will test it.

 

[v57ali]

hello
I have extracted Latitude, Longitude, Time and Speed from the response of AT+CGPSINF=32.But i have a question.
Can anybody say to me What the unit of speed is? Is Speed over Ground in knots or not?
I multiplied it at 1.85 to convert it to km/h But The speed is not correct.
The response in AT command mode with AT+CGPSINF=32 is: 32,170139.000,A,3546.343899,N,5121.076898,E,26.32,256.26,170114,,E,A
and the speed is 26*1.85=48 (km/h).
But the string in GPS/TXD is: $GPRMC,170138.000,A,3546.347408,N,05121.093972,E,51.020,,170114
and the real speed is 51*1.85=94 (km/h).
Why these speeds are different?
Please help me.
Thanks in advance