File content as of revision 2:e7f24389167b:

/* mbed GPS Module Library
 * Copyright (c) 2008-2010, sford
 * Copyright (c) 2013, B.Adryan
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */
 
#include "SerialGPS.h"

SerialGPS::SerialGPS(PinName tx, PinName rx, int baud) 
    : 
    _gps_p(new BufferedSerial(tx, rx, baud)),
    _gps(*_gps_p)
{
    longitude   = 0.0;
    latitude    = 0.0;        
}

int SerialGPS::sample() 
{
    char ns, ew, unit;
    int lock;

    while(1)
    {
        getline();

        // Check if it is a GPGGA msg (matches both locked and non-locked msg)
        if(sscanf(msg, "GPGGA,%f,%f,%c,%f,%c,%d,%d,%f,%f,%c,%f", &time, &latitude, &ns, &longitude, &ew, &lock, &sats, &hdop, &alt, &unit, &geoid) >= 1) 
        { 
            if(!lock) 
            {
                time        = 0.0;
                longitude   = 0.0;
                latitude    = 0.0;
                sats        = 0;
                hdop        = 0.0;
                alt         = 0.0;
                geoid       = 0.0;

                return 0;
            } 
            else 
            {
                //GPGGA format according http://aprs.gids.nl/nmea/#gga
                // time (float), lat (f), (N/S) (c), long (f), (E/W) (c), fix (d), sats (d),
                // hdop (float), altitude (float), M, geoid (float), M, , ,  
                //GPGGA,092010.000,5210.9546,N,00008.8913,E,1,07,1.3,9.7,M,47.0,M,,0000*5D
                
                if(ns == 'S') { latitude  *= -1.0;  }
                if(ew == 'W') { longitude *= -1.0;  }

                float degrees   = trunc(latitude / 100.0f);
                float minutes   = latitude - (degrees * 100.0f);

                latitude        = degrees + minutes / 60.0f;    
                degrees         = trunc(longitude / 100.0f * 0.01f);
                minutes         = longitude - (degrees * 100.0f);
                longitude       = degrees + minutes / 60.0f;

                return 1;
            }
        }
    }
}

float SerialGPS::trunc(float v) 
{
    if(v < 0.0) 
    {
        v*= -1.0;
        v = floor(v);
        v*=-1.0;
    } 
    else 
    {
        v = floor(v);
    }
    return v;
}

void SerialGPS::getline() 
{
    char ch;
    int idx = 0;

    while(1)
    {
        _gps.read(&ch, 1);
        if(ch != '$')
        {
            while(idx++ < 256)
            {
                if(ch == '\r')
                {
                    msg[idx] = 0;
                    return;
                }

                msg[idx] = ch;
            }
        }
    }
    fprintf(stderr, "\r\nGPS: Overflowed message limit\r\n");
    return;
    //error("Overflowed message limit");
}