mygps.c

處理與接收 gps 信號的範例碼, 使用的平台式 HOLUX GR-86.

/**
 * @file mygps.c
 *
 * @brief Operations for controlling GPS
 *
 * @copyright  Copyright (C) 2006, dmatek
 * @author chris_zhang <www.dmatek.com> 
 * @author modified, Tang-Hsun Tu (crilit), NTU GINM, Lab 408, 2008/7/4, [e-mail]
 * @version 1.0
 * @date 2008
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <termios.h>
#include <errno.h>


//---------------------------------------------------
// global data
//---------------------------------------------------
#define GPGGA_MSG "$GPGGA"
#define GPGLL_MSG "$GPGLL"
#define GPGSA_MSG "$GPGSA"
#define GPGSV_MSG "$GPGSV"
#define GPRMC_MSG "$GPRMC"
#define GPVTG_MSG "$GPVTG"
#define GPMSS_MSG "$GPMSS"
#define GPZDA_MSG "$GPZDA"
//---------------------------------------------------


//---------------------------------------------------
// function prototype
//---------------------------------------------------

//---------------------------------------------------
/**
 * @brief strtok split by , & 0
 *
 * @param 
 *    arg split argument
 */
static char *mystrtok(char *arg)
{
/* loop counter */
int i;
/* len */
int len;
/* start ptr */
static char *fptr;
/* check stop split */
static unsigned char chk_flag;
/* return ptr */
char *rptr;

    if(arg){ /* first */
        chk_flag = 0;
        len = strlen(arg);
        rptr = arg;
        fptr = arg;
    }else{ /* next split */
        len = strlen(fptr);
        rptr = fptr;
    }


    if(len == 0 || chk_flag) return NULL; /* check out ? */
    
    for(i=0; i<=len; ++i){ /* start split */
        if(fptr[i] == ','){
           fptr[i] = 0;
           fptr = fptr + i + 1;
           return rptr;
        }else if(fptr[i] == '\0'){
           chk_flag = 1;
           return rptr;
        }
    }
    
    return NULL;
}
//---------------------------------------------------
/**
 * @brief handle GPS GGA command
 *
 * @param 
 *    cmd GPS command
 */
static void handle_GPGGA(char *cmd) 
{
/* ptr */
char *sptr;
/* checksum */
char chk_sum[6];

    printf("Global Positioning System Fix Data (GGA)\n");
    
    /* get checksum */
    if((sptr = strrchr(cmd, '*'))){
        strcpy(chk_sum, sptr + 1);
        *sptr = '\0';
    }   
    
    /* get msg id */
    mystrtok(cmd);
    
    /* get UTC Time */
    if((sptr = mystrtok(NULL))){
        printf("\tUTC Time: %s\n", sptr);  
    }
    
    /* get Latitude */
    if((sptr = mystrtok(NULL))){
        printf("\tLatitude: %s\n", sptr);  
    }
    
    /* get N/S Indictor */
    if((sptr = mystrtok(NULL))){
        printf("\tN/S Indictor: %s\n", sptr);  
    }
    
    /* get Longitude */
    if((sptr = mystrtok(NULL))){
        printf("\tLongitude: %s\n", sptr);  
    }
    
    /* get E/W Indictor */
    if((sptr = mystrtok(NULL))){
        printf("\tE/W Indictor: %s\n", sptr);  
    }
    
    /* get Position Fix Indictor */
    if((sptr = mystrtok(NULL))){
        printf("\tPosition Fix Indictor: %s, ", sptr);  
        switch(atoi(sptr)){
        case 0: printf("Fix not avaiable or invalid\n"); break;
        case 1: printf("GPS SPS Mode, fix valid\n"); break;
        case 2: printf("Differential GPS, SPS Mode, fix valid\n"); break;
        case 3: printf("GPS PPS Mode, fix valid\n"); break;                        
        }
    }
    
    /* get Satellites Used */
    if((sptr = mystrtok(NULL))){
        printf("\tSatellites Used: %d\n", atoi(sptr));  
    }
    
    /* get HDOP */
    if((sptr = mystrtok(NULL))){
        printf("\tHDOP: %s\n", sptr);  
    }
    
    /* get MSL Altitude */
    if((sptr = mystrtok(NULL))){
        printf("\tMSL Altitude: %s meters\n", sptr);  
    }
    
    /* get Units */
    if((sptr = mystrtok(NULL))){
        printf("\tUnits: %s meters\n", sptr);  
    }
    
    /* get Geoid Spearation */
    if((sptr = mystrtok(NULL))){
        printf("\tGeoid Spearation: %s meters\n", sptr);  
    }
    
    /* get Units */
    if((sptr = mystrtok(NULL))){
        printf("\tUnits: %s meters\n", sptr);  
    }
    
    /* Age of Diff. Corr. */
    if((sptr = mystrtok(NULL))){
        printf("\tAge of Diff. Corr.: %s seconds\n", sptr);  
    }
    
    /* get diff. ref. station ID */
    if((sptr = mystrtok(NULL))){
        printf("\tDiff. Ref. station ID: %s\n", sptr);
    }else{
        printf("\tDiff. Ref. station ID:\n");          
    }
        
    /* show checksum */
    printf("\tChecksum: 0x%s\n", chk_sum);                                               
}
//---------------------------------------------------
/**
 * @brief handle GPS GSA command
 *
 * @param 
 *    cmd GPS command
 */
static void handle_GPGSA(char *cmd) 
{
/* ptr */
char *sptr;
/* loop counter */
int i;
/* checksum */
char chk_sum[6];

    printf("GNSS DOP and Active Satellites (GSA)\n");
    
    /* get checksum */
    if((sptr = strrchr(cmd, '*'))){
        strcpy(chk_sum, sptr + 1);
        *sptr = '\0';
    }  
    
    /* get msg id */
    mystrtok(cmd);
    
    /* get Mode 1 */
    if((sptr = mystrtok(NULL))){
        printf("\tMode 1: %s, ", sptr);
        switch(sptr[0]){
        case 'M': printf("Manual - forced to operate in 2D or 3D mode\n"); break;
        case 'A': printf("2DAutomatic - allowed to automatically switch 2D/3D\n"); break;                    
        }          
    }
    
    /* get Mode 2 */
    if((sptr = mystrtok(NULL))){
        printf("\tMode 2: %s, ", sptr); 
        switch(sptr[0]){
        case '1': printf("Fix Not Avaiable\n"); break;
        case '2': printf("2D\n"); break;
        case '3': printf("3D\n"); break;        
        }          
    }
    
    /* show channels */
    for(i=1; i<=12; ++i){
        /* Satellite Used */
        if((sptr = mystrtok(NULL))){
            if(sptr[0] != '\0')
                printf("\tSatellite Used (Sv on Channel %d): %s\n", i, sptr);  
        }          
    }
    
    /* get PDOP */
    if((sptr = mystrtok(NULL))){
        printf("\tPDOP: %s\n", sptr);  
    }
    
    /* get HDOP */
    if((sptr = mystrtok(NULL))){
        printf("\tHDOP: %s\n", sptr);  
    }    

    /* get VDOP */
    if((sptr = mystrtok(NULL))){
        printf("\tVDOP: %s\n", sptr);  
    }else{
        printf("\tVDOP: %s\n");          
    }   
    
    /* show checksum */
    printf("\tChecksum: 0x%s\n", chk_sum);   
                                            
}
//---------------------------------------------------
/**
 * @brief handle GPS GLL command
 *
 * @param 
 *    cmd GPS command
 */
static void handle_GPGLL(char *cmd) 
{
/* ptr */
char *sptr;
/* checksum */
char chk_sum[6];

    printf("Geographic Position with Latitude/Longitude (GLL)\n");
    
    /* get checksum */
    if((sptr = strrchr(cmd, '*'))){
        strcpy(chk_sum, sptr + 1);
        *sptr = '\0';
    }   
    
    /* get msg id */
    mystrtok(cmd);
    
    /* get Latitude */
    if((sptr = mystrtok(NULL))){
        printf("\tLatitude: %s\n", sptr);  
    }
    
    /* get N/S Indictor */
    if((sptr = mystrtok(NULL))){
        printf("\tN/S Indictor: %s\n", sptr);  
    }
    
    /* get Longitude */
    if((sptr = mystrtok(NULL))){
        printf("\tLongitude: %s\n", sptr);  
    }
    
    /* get E/W Indictor */
    if((sptr = mystrtok(NULL))){
        printf("\tE/W Indictor: %s\n", sptr);  
    }

    /* get UTC Position */
    if((sptr = mystrtok(NULL))){
        printf("\tUTC Position: %s\n", sptr);  
    }
   
    /* get Status */
    if((sptr = mystrtok(NULL))){
        printf("\tStatus: %s\n", sptr);        
    }else{
        printf("\tStatus:\n");           
    } 
        
    /* show checksum */
    printf("\tChecksum: 0x%s\n", chk_sum);        
}
//---------------------------------------------------
/**
 * @brief handle GPS GSV command
 *
 * @param 
 *    cmd GPS command
 */
static void handle_GPGSV(char *cmd) 
{
/* ptr */
char *sptr, *cptr;
/* satellites in view */
int sate_in_view = 0;
/* start sate */
static int start_sate = 1;
/* do message */
int num_of_msg, msg_num;
/* checksum */
char chk_sum[6];

    printf("GNSS Satellites in View (GSV)\n");

    /* get checksum */
    if((sptr = strrchr(cmd, '*'))){
        strcpy(chk_sum, sptr + 1);
        *sptr = '\0';
    }   
               
    /* get msg id */
    mystrtok(cmd);
    
    /* get number of mesages */
    if((sptr = mystrtok(NULL))){
        printf("\tNumber of Mesages: %s\n", sptr);
        num_of_msg = atoi(sptr);  
    }

    /* get Message Number */
    if((sptr = mystrtok(NULL))){
        printf("\tMessage Number: %s\n", sptr); 
        msg_num = atoi(sptr); 
        
        /* reset start satellites */
        if(msg_num == 1)
            start_sate = 1;     
    }

    /* get Satellites in View */
    if((sptr = mystrtok(NULL))){
        printf("\tSatellites in View: %s\n", sptr);
        sate_in_view = atoi(sptr);  
    }
    
    /* handle satellites */
    for(; start_sate<=sate_in_view; ++start_sate){
        /* get Satellite ID */
        if((sptr = mystrtok(NULL))){
            printf("\tSatellite %d (ID: %s)\n", start_sate, sptr);  
        }else break; /* no item */
        
        /* get Elevation */
        if((sptr = mystrtok(NULL))){
            printf("\tElevation: %s\n", sptr);  
        }        

        /* get Azimuth */
        if((sptr = mystrtok(NULL))){
            printf("\tAzimuth: %s\n", sptr);  
        }
        
        /* get SNR (C/No), check with checksum */
        if((sptr = mystrtok(NULL))){
            printf("\tSNR (C/No): %s\n", sptr);  
        }else{
            printf("\tSNR (C/No):\n");         
        }                        
    }
    
    /* show checksum */
    printf("\tChecksum: 0x%s\n", chk_sum);      
}
//---------------------------------------------------
/**
 * @brief handle GPS RMC command
 *
 * @param