// this is a test about GPS Receiver #include <stdio.h>#include <string.h>#include <stdlib.h>#include <fcntl.h>      // open() close()#include <unistd.h>     // read() write()#include <termios.h>    // set baud rate#include <fcntl.h>#include <sys/select.h>#include <sys/time.h>#include <sys/types.h>#define DEVICE_TTYS "/dev/ttyS2"#define BAUD_RATE_9600 B9600#define FUNC_RUN                0#define FUNC_NOT_RUN            1#define ORG_GPS		1#define SEL_GPGGA	2#define SEL_GPGLL	3#define SEL_GPGSA	4#define SEL_GPGSV	5#define SEL_GPRMC	6#define SEL_GPVTG	7#define FUNC_QUIT	8//------------------------------------- read datas from GPS -------------------------------------------------// succese return 1// error   return 0int read_GPS_datas(int fd, char *rcv_buf){	int retval;        fd_set rfds;        struct timeval tv;        int ret,pos;        tv.tv_sec = 1;        tv.tv_usec = 0;        pos = 0; // point to rceeive buf        while (1)        {                FD_ZERO(&rfds);                FD_SET(fd, &rfds);                retval = select(fd+1 , &rfds, NULL, NULL, &tv);                if (retval == -1)                {                        perror("select()");                        break;                }                else if (retval)                {// pan duan shi fou hai you shu ju                        ret = read(fd, rcv_buf+pos, 2048);                        pos += ret;                        if (rcv_buf[pos-2] == '\r' && rcv_buf[pos-1] == '\n')                        {                                FD_ZERO(&rfds);                                FD_SET(fd, &rfds);                                retval = select(fd+1 , &rfds, NULL, NULL, &tv);                                if (!retval) break;// if no datas, break                        }                }                else                {                        printf("No data\n");                        break;                }        }        return 1;} // end read_GPS_datas//------------------------------------- print ---------------------------------------------------------------void print_prompt(void){        printf ("Select what you want to read:\n");        printf ("1 : Original GPS datas\n");        printf ("2 : GPGGA\n");        printf ("3 : GPGLL\n");        printf ("4 : GPGSA\n");        printf ("5 : GPGSV\n");        printf ("6 : GPRMC\n");	printf ("7 : GPVTG\n");	printf ("8 : Quit\n");        printf (">");} // end print_prompt//------------------------------------- FUNCTIONS ABOUT GPS -------------------------------------------------//------------------------------------- FUNCTION 1 show all receive signal ----------------------------------void GPS_original_signal(int fd){	char rcv_buf[2048];	while (1)	{		bzero(rcv_buf,sizeof(rcv_buf));		{			if (read_GPS_datas(fd,rcv_buf))			{				printf("%s",rcv_buf);			}		}	}} // end GPS_original_signal//------------------------------------- FUNCTION 2 resolve GPS GPGGA information ----------------------------void GPS_resolve_gpgga(int fd){} // end GPS_resolve_gpgga//------------------------------------- FUNCTION 3 resolve GPS GPGLL information ----------------------------void GPS_resolve_gpgll(int fd){} // end GPS_resolve_gpgll//------------------------------------- FUNCTION 4 resolve GPS GPGSA information ----------------------------void GPS_resolve_gpgsa(int fd){} // end GPS_resolve_gpgsa//------------------------------------- FUNCTION 5 resolve GPS GPGSV information ----------------------------void GPS_resolve_gpgsv(int fd){} // end GPS_resolve_gpgsv//------------------------------------- FUNCTION 6 resolve GPS GPRMC information ----------------------------void GPS_resolve_gprmc(int fd){} // end GPS_resolve_gprmc//------------------------------------- FUNCTION 7 resolve GPS GPVTG information ----------------------------void GPS_resolve_gpvtg(int fd){} // end GPS_resolve_gpvtg//------------------------------------- Receive GPS Signal --------------------------------------------------void func_GPS(int fd){        int flag_func_run;        int flag_select_func;        ssize_t ret;        flag_func_run = FUNC_RUN;        while (flag_func_run == FUNC_RUN)        {                print_prompt();                 // print select functions                scanf("%d",&flag_select_func);  // user input select                getchar(); // get ENTER <LF>                switch(flag_select_func)                {			case ORG_GPS	: {GPS_original_signal(fd);	break; }                        case SEL_GPGGA	: {GPS_resolve_gpgga(fd);	break; }                        case SEL_GPGLL	: {GPS_resolve_gpgll(fd);	break; }                        case SEL_GPGSA	: {GPS_resolve_gpgsa(fd);	break; }                        case SEL_GPGSV  : {GPS_resolve_gpgsv(fd);       break; }                        case SEL_GPRMC	: {GPS_resolve_gprmc(fd);       break; }			case SEL_GPVTG	: {GPS_resolve_gpvtg(fd);	break; }                        case FUNC_QUIT          :                                                {                                                        flag_func_run = FUNC_NOT_RUN;                                                        printf("Quit GPS function.  byebye\n");                                                        break;                                                }                        default :                        {                                printf("please input your select use 1 to 8\n");                        }                }        }}// end func_GPS//------------------------------------- init seriel port  ---------------------------------------------------void init_ttyS(int fd){	struct termios newtio;	bzero(&newtio, sizeof(newtio));	newtio.c_lflag &= ~(ECHO | ICANON);	newtio.c_cflag = B9600 | CS8 | CLOCAL | CREAD;	newtio.c_iflag = IGNPAR;	newtio.c_oflag = 0;	newtio.c_oflag &= ~(OPOST);	newtio.c_cc[VTIME]    = 5;   /* inter-character timer unused */	newtio.c_cc[VMIN]     = 0;   /* blocking read until 9 chars received */	tcflush(fd, TCIFLUSH);	tcsetattr(fd,TCSANOW,&newtio);}//end init_ttyS//------------------------------------- main ----------------------------------------------------------------int main(void){	int fd;	printf ("\nThis is a test about GPS : receive GPS signal\n\n");	// open seriel port        fd = open(DEVICE_TTYS, O_RDONLY);	if (fd == -1)        {                printf("open device %s error\n",DEVICE_TTYS);        }        else        {                init_ttyS(fd);  // init device        	func_GPS(fd);   // GPS functions                // close ttyS0                if (close(fd)!=0) printf("close device %s error",DEVICE_TTYS);        }	return 0; } // end main