How to interface GPS to PC???

[Eng_Girl]

gps interfacing turbo c

Hi,

I want to ask, how can I interface my GPS receiver GARMIN through serial cable to the computer using the C compiler Dev-C++ ?

Is there any special things to do before ?

Do I need to store the GPS data first or process it directly by the program ?

If anyone have the C code for such interfacing PLZ give it to me????


Thanks,

 

[jallem]

gprmc sscanf c

I dont have any information about that particular
GPS receiver(Garmin) but I used Motorola Oncore
before. In it the serial port was automatically bumping
data in the format that you select.

 

[techie]

Garmin GPS like most other GPS send serial data stream as NMEA protocol which is 4800baud, 8bits, no parity, 1 stop bit. The data is streamed continously so you need to configure a receive only serial port. You dont need to transmit anything.
I have done a lot of serial programming but havent used DEV-C. If you follow a DOS style program, you can use scanf to get the data stream in a string variable.

 

[Eng_Girl]

Thanks for replying , I kind of having a C code for parsing the GPRMC sentences ,but now I want to connect it to the serial port of my computer , how can I do that ,what libraries to use and how to determine the serial port .

any hint may help , thanks...

 

[techie]

You can begin with a test with the hyperterminal. That will let you know which serial port is it COM1 or COM2. I dont know about DevC but in old C's like turbo-C you could read the serial port using the following
main() {
unsigned char chr;
int port_ads = 0x3f8;


_bios_serialcom(_COM_INIT, PORTNO,
_COM_9600 | _COM_STOP1 | _COM_NOPARITY | _COM_CHR8);
printf("initialized\n");

for ( ; ; ) {
if (kbhit() ) {
chr = getch();
if (chr == 27) break; // terminate on ESC
outp(port_ads, chr);
delay (10); // 10ms to respond
chr = inp(port_ads);
printf("Result = %d",chr);
putchar ('\n');
}
}
exit(0);
}

If you send me your code, maybe I can add some code for GPS in it. I have a GPS receiver and am kinda looking into learnig DevC also.

 

[Eng_Girl]

This is my code I first test the parsing of the GPS data to GPRMC , I define this sentence as a string array ,I run it it works,but now how can I modify it to read from the serial port instead.
can u explain to me each line of the code u provide it, please :?:

/******************************************************************************
*GPS.C is a program to test the parsing of the GPS sentence $GPRMC 
* and divide it into the required feilds: 
*Time ,Date, Latitude,Longitude,speed     
*******************************************************************************/     
#include <string.h>
#define paws system("PAUSE"); // to pause the output window in DEV-C++ program
#define MAXSIZE 100
#define COMMA   0x2C

 main(){ 
// char read from COM port
 
 char  charRead[]="$GPRMC,123519,A,4807.038,N,01131.000,E,022.4,084.4,230394,003.1,W*6A"; 
  

//	Buffer collects chars read from GPS
 char  stringRead[MAXSIZE];
	
//	Set an array for each attribute
  unsigned char  tempString[MAXSIZE];
  unsigned char  timeString[12];
  unsigned char  latitudeString[12];
  unsigned char  latitudeCardinalString[3];
  unsigned char  longitudeString[12];
  unsigned char  longitudeCardinalString[3];
  unsigned char  speedString[11];
  unsigned char  dateString[12];

//	Declare pointer
  unsigned char  *pChar;

//	Coordinated Universal Time(GMT) & Eastern Standard time
 unsigned  long utcTime, estTime;
 unsigned  long utcHour, estHour;
 unsigned  long utcMinutes, estMinutes;
 unsigned  long utcSeconds, estSeconds;
 unsigned  long date;
 unsigned  long day,month,year;

//	Sets the last comma position
 unsigned  char lastCommaPosition;

//	Sets the Latitude & Longitude
  float	latitude;
  int	latDegrees;
  float	latMinutes;

  float 	longitude;
  int	    longDegrees;
  float	    longMinutes;
  float     speed;

//	dummy variable
	unsigned int   j, k;
	
//	Number of chars read per GPS message string
	unsigned int	 i;

//	initializing the serial ports SCI0 & SCI1 

//	Enter a loop for reading char from serial port(Data Reg.)

//do {	

// checks if GPS messages start with $  char
 
if (charRead [0] == '$'){ 
              
	  i = 1;


   while(i<MAXSIZE){
	  stringRead[i] = charRead[i];  //  include each char read to the array 
	  i++;
   }  
       
 /* By this point, a complete GPS string has been read so save it*/	     
 /* Append the null terminator to the string read */
	  stringRead[i+1] = '\0';

	  /* Analyze string that we collected */
	   j = 0;
	  pChar = stringRead;     // put a pointer for the stringRead array
   while(*(pChar+j) != COMMA) {       /* COMMA  0x2C */

	       tempString[j] = *(pChar+j); //store the string before the comma
	       j++;
   }

	  tempString[j] = '\0';   // append the null to the end 

	  /* Check if string we collected is the $GPRMC message */
	  if (tempString[3] == 'R' && tempString[4] == 'M' && tempString[5] == 'C'){ 

/* Found GPRMC string. It has 11 commas total. Its NMEA sentence structure is:

$GPRMC,123519,A,4807.038,N,01131.000,E,022.4,084.4,230394,003.1,W*6A

Where:
     RMC          Recommended Minimum sentence C
     123519       Fix taken at 12:35:19 UTC
     A            Status A=active or V=Void.
     4807.038,N   Latitude 48 deg 07.038' N
     01131.000,E  Longitude 11 deg 31.000' E
     022.4        Speed over the ground in knots 
     084.4        Track angle in degrees True
     230394       Date - 23rd of March 1994
     003.1,W      Magnetic Variation
     *6A          The checksum data, always begins with *
*/

	pChar = stringRead;  // pointer to the String read

// (1) Get UTC time 

	      j = 7;  /* start of time field */
	      k = 0;
		  
	      while(*(pChar+j) != COMMA) { //loop until a comma is found
		   timeString[k] = *(pChar+j);   //save in the time string
		   	j++;
		   	k++;
	      }

	    lastCommaPosition = j; //  save the position of the last comma
	    timeString[k] = '\0'; // append the null to the end 

	   sscanf(timeString, "%ld", &utcTime); //save the string to the variable 

	    utcHour = (utcTime/10000); //extract Hours from long 
	    utcMinutes = (utcTime - (utcHour*10000))/100;  //extract minutes from long 
	    utcSeconds = utcTime - (utcHour*10000) -  (utcMinutes*100);  /* extract seconds from long */

	      if(utcHour >= 0 && utcHour <= 20) 
		      estHour = utcHour + 3;
		  
	      else 
              estHour = utcHour - 21;
              
	      estMinutes =  utcMinutes;
	      estSeconds =  utcSeconds;
		 
	
// (2) Empty Loop to avoid taking 'A' char

          pChar = stringRead;
	      j = lastCommaPosition + 1; //start from the next comma 
	      k = 0;
	      
	      while(*(pChar+j) != COMMA) {
		   j++;
		   k++;
	      }
	      lastCommaPosition = j;


// (3) Get lattitude 

	      pChar = stringRead;
	      j = lastCommaPosition +1; //start from the next comma 
	      k = 0;
	      while(*(pChar+j) != COMMA) {
		   latitudeString[k] = *(pChar+j); //save in the latitude string
		   j++;
		   k++;
	      }
	      lastCommaPosition = j;
	      latitudeString[k] = '\0';

	      sscanf(latitudeString, "%f", &latitude);
	      latDegrees = (int)(latitude/100);
	      latMinutes = (float)(latitude - latDegrees*100);

// (4)  Get lattitude Cardinal direction 

	      pChar = stringRead;
	      j = lastCommaPosition + 1;
	      k = 0;
		  
	      while(*(pChar+j) != COMMA) {
		   latitudeCardinalString[k] = *(pChar+j);
		   j++;
		   k++;
	      }
	      lastCommaPosition = j;
	      latitudeCardinalString[k] = '\0';
	      

// (5) Get longitude

	      pChar = stringRead;
	      j = lastCommaPosition + 1;
	      k = 0;

	      while(*(pChar+j) != COMMA) {
		   longitudeString[k] = *(pChar+j);
		   j++;
		   k++;
	      }

	      lastCommaPosition = j;
	      longitudeString[k] = '\0';

	      sscanf(longitudeString, "%f", &longitude);
	      longDegrees = (int)(longitude/100);
	      longMinutes = (float)(longitude - longDegrees*100);

// (6) Get longitude Cardinal direction 

	      pChar = stringRead;
	      j = lastCommaPosition + 1;
	      k = 0;
		  
	      while(*(pChar+j) != COMMA) {
		   longitudeCardinalString[k] = *(pChar+j);
		   j++;
		   k++;
	      }
	      lastCommaPosition = j;
	      longitudeCardinalString[k] = '\0';
	      
	
// (7) Get Speed in Knots 
      	     
          pChar = stringRead;
	      j = lastCommaPosition + 1;
	      k = 0;

	      while(*(pChar+j) != COMMA) {
		   speedString[k] = *(pChar+j);
		   j++;
		   k++;
	      }

	      lastCommaPosition = j;
	      speedString[k] = '\0';

	      sscanf(speedString, "%f", &speed);
	      speed = speed * 1.852; //convert the speed in Knots to Km/hour
	      

// (8) Empty Loop to avoid taking the Track angle 

          pChar = stringRead;
	      j = lastCommaPosition + 1; 
	      k = 0;
	      while(*(pChar+j) != COMMA) {
		   j++;
		   k++;
	      }
	      lastCommaPosition = j;


// (9) Get date 

	      pChar = stringRead;
	      j = lastCommaPosition + 1;  
	      k = 0;

	      while(*(pChar+j) != COMMA) {
		   dateString[k] = *(pChar+j);
		   j++;
		   k++;
	      }

	      lastCommaPosition = j;
	      dateString[k] = '\0';

	      sscanf(dateString, "%ld", &date);

	     day = (date/10000); //extract day from long 
	     month = (date - (day*10000))/100;  // extract month from long 
	     year = date - (day*10000) - (month*100); // extract year from long             

	 
//else not a GPRMC sentence
} 

// otherwise not a $ character... so loop back until one arrives
} 
//  } while(1);
printf(" \t GPRMC Sentence Test\n");
printf(" **********************************************************\n" );
printf(" **********************************************************\n\n" );
printf("   Time  :  %02ld:%02ld:%02ld UTC = %02ld:%02ld:%02ld EST \n\n", utcHour, utcMinutes, utcSeconds, estHour, estMinutes, estSeconds);
printf("   Date  :  %02ld:%02ld:%02ld  \n\n", day, month, year);
printf(" ----------------------------------------------------------\n" );
printf("   Latitude   :\t  %02d DEG  %2.4f MIN ", latDegrees, latMinutes);
printf(" %s \n\n", latitudeCardinalString);
printf("   Longitude  :\t %03d DEG %2.4f MIN ", longDegrees, longMinutes);
printf(" %s \n\n", longitudeCardinalString);
printf("   Speed      :  %f  Km/hour \n\n", speed );
printf(" **********************************************************\n\n" );

paws //to end the pause function declared above

} /* end of main */

 

[techie]

Actually serial port access is different in different programming Environments. I had used it in DOS days of Turbo C whose code I pased. Now it has two parts.

#1 is to initialize the port to set the baud rate and other things. _bios_serialcom(...) does this part.

#2 is to get teh data from serial port into some buffer. inp(port_ads); does that part.

The functions of Dev-C would differ. You may have to search for these. I will also search and let you know if I find them.

Are you making a console application or a Window application?