File content as of revision 12:a895e3581542:

#include "mbed.h"
#include "max32630fthr.h"
#include <stdbool.h>
#define on 1
#define off 0

Serial pc(USBTX, USBRX);
Serial gps(P5_3, P5_4, 9600);
I2C i2c(P5_7,P6_0); // SDA, SCL

DigitalOut red_led(LED1,1);
DigitalOut green_led(LED2,1);
DigitalOut blue_led(LED3,1);

char gpsfix_last_utc_time[11] = {0};
char gpsfix_last_utc_date[7] = {0};
char gpsfix_longtitude[12] = {0};
char gpsfix_latitude[12] = {0};
char gpsfix_speed[8] = {0};     //Set but not used
char gpsfix_course[7] = {0};    //Set but not used
char gpsfix_variation[7] = {0}; //Set but not used
char gpsfix_mag_var_ew[1] = {0};//Set but not used
char gpsfix_ns = 0;
char gpsfix_ew = 0;


void gps_power(bool state)
{
    char    data[2];
    data[0] = 0x16;     //MAX14690 LDO3cfg register
    data[1] = 0xE0;     //Disable LDO3
    if (state == on) {
        data[1] = 0xE2; //Enable LDO3
    }
    i2c.write( 0x50, data, 2 );
}

void set_epoch_from_last_gps_time(void)
{
    struct tm t;
    time_t t_of_day;
    char two_char_str[3] = {0};
    memcpy(two_char_str, gpsfix_last_utc_date+4, 2);
    t.tm_year = atoi(two_char_str)+100;         //Years since 1900
    memcpy(two_char_str, gpsfix_last_utc_date+2, 2);
    t.tm_mon = atoi(two_char_str)-1;            // Month, 0 - jan gpsfix_last_utc_date
    memcpy(two_char_str, gpsfix_last_utc_date, 2);
    t.tm_mday = atoi(two_char_str);             // Day of the month gpsfix_last_utc_date
    memcpy(two_char_str, gpsfix_last_utc_time, 2);
    t.tm_hour = atoi(two_char_str);
    memcpy(two_char_str, gpsfix_last_utc_time+2, 2);
    t.tm_min = atoi(two_char_str);
    memcpy(two_char_str, gpsfix_last_utc_time+4, 2);    
    t.tm_sec = atoi(two_char_str);
    t.tm_isdst = 0;        // Is DST on? 1 = yes, 0 = no, -1 = unknown
    t_of_day = mktime(&t);
    printf("seconds since the Epoch: %ld\n", (long) t_of_day);
}

void gps_update(void)
{
    gps_power(on);
    bool wait_for_fix = true;
    while (wait_for_fix) {
        int checksum = 0;
        char nmea_sentence[82] = {0};   //Fill with NULL terminators to save doing it later
        while (gps.getc()!='$');        //wait for start of sentence
        int nmea_index = 0;
        nmea_sentence[nmea_index] = '$';    //Manually insert the '$' because we don't want it included in the checksum loop
        char nmea_char = gps.getc();        //get sentence first char from GPS
        while (nmea_char != '*') {          //Loop building sentence and calc'ing CS until *
            checksum ^= nmea_char;         //Calc checksum as we read sentence
            if ((nmea_sentence[nmea_index] == ',')&&(nmea_char == ',')) {
                nmea_sentence[++nmea_index] = ' ';  //Pad consecutive comma with a space to make it possible to use strtok with empty values
            }
            nmea_sentence[++nmea_index] = nmea_char; //build the sentence with the next character
            if (nmea_index > 80) {
                nmea_index=80;          //Don't overflow buffer
            }
            nmea_char = gps.getc();     //get next char from GPS
        }
        //Last character was the '*' so read the two hex digits of CS from gps
        char hex_checksum[3] = {0};
        hex_checksum[0] = gps.getc();
        hex_checksum[1] = gps.getc();
        if (checksum == (int)strtol(hex_checksum, NULL, 16) ) {
            //Valid sentence so check if it's a GPRMC
            //pc.printf("Match\n\r");
            const char gprmc[7] = "$GPRMC";
            char *token;
            token = strtok(nmea_sentence, ",");
            if (strcmp(token,gprmc) == 0) {     //GPRMC ?
                pc.printf( " %s\n\r", token );  //Get the time
                if (token != NULL) {
                    token = strtok(NULL, ",");
                    if (*token != 32) {         //If there is a time present, record it.
                        pc.printf("Time: %s\n\r",token);
                        memcpy(gpsfix_last_utc_time, token, sizeof gpsfix_last_utc_time - 1);
                    }
                }
                if (token != NULL) {
                    token = strtok(NULL, ",");
                    if (*token == 'V') {
                        pc.printf("VOID");
                    }
                }
                if (*token == 'A') {                //Is this an 'A'ctive (valid) fix?
                    pc.printf("Got a fix\n\r");
                    gps_power(off);                 //Yes - No need for GPS now
                    wait_for_fix = false;           //Stop looping now we have a fix.
                    while (gps.readable()) {
                        char dummy = gps.getc();    //Empty serial buffer because overflows reveal MBED bugs :-(
                    }
                    if (token != NULL) {
                        token = strtok(NULL, ",");
                        //pc.printf("Latitude: %s\n\r",token);
                        memcpy(gpsfix_latitude, token, sizeof gpsfix_latitude - 1);
                    }
                    if (token != NULL) {
                        token = strtok(NULL, ",");
                        //pc.printf("North/South: %s\n\r",token);
                        gpsfix_ns = *token;
                    }
                    if (token != NULL) {
                        token = strtok(NULL, ",");
                        //pc.printf("Longitude: %s\n\r",token);
                        memcpy(gpsfix_longtitude, token, sizeof gpsfix_longtitude - 1);
                    }
                    if (token != NULL) {
                        token = strtok(NULL, ",");
                        //pc.printf("East/West: %s\n\r",token);
                        gpsfix_ew = *token;
                    }
                    if (token != NULL) {
                        token = strtok(NULL, ",");
                        //pc.printf("Speed in knots: %s\n\r",token);
                    }
                    if (token != NULL) {
                        token = strtok(NULL, ",");
                        //pc.printf("True course: %s\n\r",token);
                    }
                    if (token != NULL) {
                        token = strtok(NULL, ",");
                        //pc.printf("Date: %s\n\r",token);
                        memcpy(gpsfix_last_utc_date, token, sizeof gpsfix_last_utc_date - 1);
                    }
                    if (token != NULL) {
                        token = strtok(NULL, ",");
                        //pc.printf("Variation: %s\n\r",token);
                    }
                    if (token != NULL) {
                        token = strtok(NULL, ",");
                        //pc.printf("Variation East/West: %s\n\r",token);
                    }
                }
            }
        }
        while (gps.readable()) {
            char dummy = gps.getc();
        }
    }
}

int main()
{
    char    data[2];
    data[0] = 0x1A;     //MAX14690 BootCfg register
    data[1] = 0x30;     //Always-On Mode, off state via PWR_OFF_CMD
    i2c.write( 0x50, data, 2 );

    data[0] = 0x17;     //MAX14690 LDO3Vset register
    data[1] = 0x19;     //3.3V
    i2c.write( 0x50, data, 2 );
    gps_power(off);
    wait(2);
    while (1) {
        gps_update();
        set_epoch_from_last_gps_time();
        wait(600);
    }
}