Code Analysis for NMEA GPS String

Question

I am trying to parse an incoming GPGGA NMEA GPS line using Arduino uno and below code. What I'm trying to do is that I only use the GPGGA NMEA string to get the latitude, longitude and altitude. In my lower code, I set certain checks to check if the incoming line is GPGGA or not, and then save the further line in an array, which can be further analyzed using the strtok function and all 3 GPS coordinates can be easily detected.

But I can’t figure out how to store only the GPGGA line, not the further line. I use a for loop, but it does not work.

I am not trying to use any library. I came across certain existing codes like this.

GPGGA

i) , GPGGA ii) , EOL * ( ) , ( ) iii) ( , )

 #include <SoftwareSerial.h>

    SoftwareSerial mySerial(10,11);  // 10 RX / 11 TX

    void setup()
    {
    Serial.begin(9600);
    mySerial.begin(9600);
    }

    void loop()
    {
    uint8_t x;
    char gpsdata[65];

    if((mySerial.available()))
    {
    char c = mySerial.read();
    if(c == '$')
      {char c1 = mySerial.read();
       if(c1 == 'G')
         {char c2 = mySerial.read();
          if(c2 == 'P')
            {char c3 = mySerial.read();
             if(c3 == 'G')
               {char c4 = mySerial.read();
                if(c4 == 'G')
                   {char c5 = mySerial.read();
                    if(c5 == 'A')
                       {for(x=0;x<65;x++)
                        { 
                        gpsdata[x]=mySerial.read();


    while (gpsdata[x] == '\r' || gpsdata[x] == '\n')
                    {
                    break;
                    }

                        }

                       }
                       else{
                          Serial.println("Not a GPGGA string");
                        }
                   }
               }

            }     

         }

      }

    }

    Serial.println(gpsdata);
    }

1: , for .

pic, undefined .

:

$GPGGA,092750.000,5321.6802,N,00630.3372,W,1,8,1.03,61.7,M,55.2,M,,*76
$GPGSA,A,3,10,07,05,02,29,04,08,13,,,,,1.72,1.03,1.38*0A
$GPGSV,3,1,11,10,63,137,17,07,61,098,15,05,59,290,20,08,54,157,30*70
$GPGSV,3,2,11,02,39,223,19,13,28,070,17,26,23,252,,04,14,186,14*79
$GPGSV,3,3,11,29,09,301,24,16,09,020,,36,,,*76
$GPRMC,092750.000,A,5321.6802,N,00630.3372,W,0.02,31.66,280511,,,A*43
$GPGGA,092751.000,5321.6802,N,00630.3371,W,1,8,1.03,61.7,M,55.3,M,,*75
$GPGSA,A,3,10,07,05,02,29,04,08,13,,,,,1.72,1.03,1.38*0A
$GPGSV,3,1,11,10,63,137,17,07,61,098,15,05,59,290,20,08,54,157,30*70
$GPGSV,3,2,11,02,39,223,16,13,28,070,17,26,23,252,,04,14,186,15*77
$GPGSV,3,3,11,29,09,301,24,16,09,020,,36,,,*76
$GPRMC,092751.000,A,5321.6802,N,00630.3371,W,0.06,31.66,280511,,,A*45

Answer 1

NMEA 0183 :

<CR><LF> .

, , , . , .

, - , , - ( , , strlen).

Answer 2

, ...

if() - :

EDIT ​​ myString .

char globalString[100];//declare a global sufficiently large to hold you results


void loop() 
{
    int chars = mySerial.available();
    int i;
    char *myString;
    if (chars>0)
    {
        myString = calloc(chars+1, sizeof(char));
        for(i=0;i<chars;i++)
        {
            myString[i] = mySerial.read();
            //test for EOF
            if((myString[i] == '\n') ||(myString[i] == '\r'))
            {
                //pick this...
                myString[i]=0;//strip carriage - return line feed(or skip)
                //OR pick this... (one or the other. i.e.,I do not know the requirements for your string)
                if(i<chars)
                {
                    myString[i+1] = mySerial.read() //get remaining '\r' or '\n'
                    myString[i+2]=0;//add null term if necessary
                }

                break;
            }
        }
        if(strstr(myString, "GPGGA") == NULL)
          {
               Serial.println("Not a GPGGA string");   
               //EDIT
               strcpy(globalString, "");//if failed, do not want globalString populated
          }
          else
          {    //EDIT
               strcpy(globalString, myString);
          }

    }
    //free(myString) //somewhere when you are done with it
}

mySerial.available() , .

Answer 3

, .

import serial
import time
ser = serial.Serial(1)

ser.read(1)
read_val = ("nothing")

gpsfile="gpscord.dat"
l=0

megabuffer=''
def buffThis(s):
        global megabuffer
        megabuffer +=s
def buffLines():
        global megabuffer
        megalist=megabuffer.splitlines()
        megabuffer=megalist.pop()
        return megalist

def readcom():
        ser.write("ati")
        time.sleep(3)
        read_val = ser.read(size=500)
        lines=read_val.split('\n')
        for l in lines:
                if l.startswith("$GPGGA"):
                        if l[:len(l)-3].endswith("*"):
                                outfile=open('gps.dat','w')
                                outfile.write(l.rstrip())
                                outfile.close()

readcom()

while 1==1:
    readcom()

answer=raw_input('not looping , CTRL+C to abort')

: gps.dat

$GPGGA,225714.656,5021.0474,N,00412.4420,W,0,00,50.0,0.0,M,18.0,M,0.0,0000*5B

Answer 4

, . 8 9 tx rx

Main.c gps.h gps.c

Answer 5

, . 8 9 tx rx

• gps.h
• main.c
• gps.c

Answer 6

"malloc" , , . ( free(). .) , - , 10 , . .

C , strtok() , , .

. , .:)

Answer 7

You can use some functions from the libnmea C library . Theres function breaks a sentence into comma-separated values ​​and then parses them.