File content as of revision 0:6a32515035ec:

/* mbed GPS Logger using SD Card
 * 
 * Copyright (c) 2013 m.prinke, MIT License
 *
 * 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.
 *
 * @file          main.cpp 
 * @purpose       GPS Logger using SD Card
 * @version       0.1
 * @date          Feb 2013
 * @author        M. Prinke 
 */
/**   
 * Writes any serial data received from a GPS receiver to an logfile on an SD Card.
 * Logging is started/stopped using a toggle button.
 * Everytime logging is started, a new file with the filename pattern /sd/gpslog<nnnn>.txt
 * is created, where <nnnn> is decimal number in the range 0000 to 9999 which is incremented.
 * Searching for a new unique filename is started from zero. 
 */

#include "mbed.h"
#include "SDFileSystem.h"

#define GPS_BAUDRATE 4800
#define DEBUG
 
SDFileSystem sd(p5, p6, p7, p8, "sd"); // mosi, miso, sclk, cs

Serial pc(USBTX, USBRX);    // tx, rx
Serial gps(p28, p27);       // tx, rx
DigitalIn button(p21);      // button connects pin to GND
DigitalOut led_log(LED1);   // logging active


/**
 * Function to create a unique filename
 *
 * @param fn pointer to a filename buffer
 * @return 0 on success, -1 if no unused filename could be created.
 */
int get_filename(char *fn)
{
    FILE *fp;
    
    for (int n=0; n < 9999; n++) {
        sprintf(fn, "/sd/gpslog%04d.txt", n);
        if ((fp = fopen(fn, "r")) == NULL) {
            // file does not exist yet
            return 0;
        } else {
            fclose(fp);
        }
    }
    
    // filename pattern exhausted
    return -1;
}


int main() {
    char ch;
    char filename[30];
    
    button.mode(PullUp);
    gps.baud(GPS_BAUDRATE);
    
    while (1) {
        led_log = 0;
        
        #if defined(DEBUG)
        pc.printf("\n--------------------------------------------\n");
        pc.printf("GPS logging stopped, press button to start.\n");
        pc.printf("--------------------------------------------\n");
        #endif
        
        while (button);     // wait until button pressed
        wait_ms(50);        // button debounce
        while (!button);    // wait until button released
        if (get_filename(filename) != 0) {
            error("Could not create file with unique name\n");
        }
        
        #if defined(DEBUG)
        pc.printf("\n--------------------------------------------\n");
        pc.printf("GPS logging started, press button to stop.\n");
        pc.printf("Current logfile: %s\n", filename);
        pc.printf("--------------------------------------------\n");
        #endif
        
        led_log = 1;
        
        // open file for writing
        FILE *fp = fopen(filename, "w");
        if(fp == NULL) {
            error("Could not open file for write\n");
        }
        
        /*
         * Write GPS data to file until button is pressed or
         * a write error occurs.
         */
        int rv = 0;
        do {
            if(gps.readable()) {
                ch = gps.getc();
                #if defined(DEBUG)
                pc.putc(ch);
                #endif
                rv = fputc(ch, fp);
            }
        } while ((rv != EOF) && button);
        
        // close file
        fclose(fp);
        
        wait_ms(50);        // button debounce
        while (!button);    // wait until button released
    }
}