File content as of revision 4:82d2fced184b:

#include "gps.h"

void GPSDecoder::set_nmea_message(char *nmea_msg)
{
    strcpy(nmea_line, nmea_msg);
}

void GPSDecoder::decode()
{
    char *nmea_lines[MAXTOKEN];
    //printf("%s\r\n", nmea_msg);
    if (validate() != 0) {
        printf("invalid message\n");
        return;
    }

    uint8_t nmea_line_index = split(nmea_line, ',', nmea_lines, MAXTOKEN);
#if 0
    for (int i = 0; i < nmea_line_index; i++) {
        printf("[%2d]%s\r\n", i, nmea_lines[i]);
    }
#endif

    if (strcmp((nmea_lines[0]) + 3, "RMC") == 0) {
        double decimal_part[2] = {0};

        /* 時刻のデコード */
        hour = (uint8_t)str2int(nmea_lines[1], 2);
        min = (uint8_t)str2int(nmea_lines[1] + 2, 2);
        sec = (uint8_t)str2int(nmea_lines[1] + 4, 2);
        msec = (uint16_t)str2int(nmea_lines[1] + 7, 3);

        /* 日付のデコード */
        day = (uint8_t)str2int(nmea_lines[9], 2);
        month = (uint8_t)str2int(nmea_lines[9] + 2, 2);
        year = (uint16_t)str2int(nmea_lines[9] + 4, 2) + 2000;

        if (nmea_lines[2][0] == 'A') {
            //printf("RMC mode: Information\r\n");
        } else if (nmea_lines[2][0] == 'V') {
            //printf("RMC mode: Warning\r\n");
        } else {
            printf("RMC mode: invalid");
            return;
        }
        if (nmea_lines[2][0] == 'A') {
            if (nmea_lines[2][0] == 'A') {
                /* 位置情報のデコード */
                decimal_part[0] = modf(strtof(nmea_lines[3], NULL), &latitude); // 秒
                latitude /= 100;
                decimal_part[1] = floor((modf(latitude, &latitude) * 100) + 0.5); // 分
                latitude += (decimal_part[1] + decimal_part[0]) / 60;

                if (nmea_lines[4][0] == 'S')
                    latitude = -latitude;

                decimal_part[0] = modf(strtof(nmea_lines[5], NULL), &longitude); // 秒
                longitude /= 100;
                decimal_part[1] = floor((modf(longitude, &longitude) * 100) + 0.5); // 分
                longitude += (decimal_part[1] + decimal_part[0]) / 60;

                if (nmea_lines[6][0] == 'W')
                    longitude = -longitude;

                /* 移動速度のデコード */
                speed = strtof(nmea_lines[7], NULL) * 1.852f; // knot to km/h

                move_direction = strtof(nmea_lines[8], NULL);
            }
        } else {
            longitude = 0;
            latitude = 0;
        }
    } else if (strcmp((nmea_lines[0]) + 3, "GGA") == 0) {
        double decimal_part[2] = {0};

        /* 時刻のデコード */
        hour = (uint8_t)str2int(nmea_lines[1], 2);
        min = (uint8_t)str2int(nmea_lines[1] + 2, 2);
        sec = (uint8_t)str2int(nmea_lines[1] + 4, 2);
        msec = (uint16_t)str2int(nmea_lines[1] + 7, 3);

        // GGAでは日付は不明

        /* 位置情報のデコード */
        decimal_part[0] = modf(strtof(nmea_lines[2], NULL), &latitude); // 秒
        latitude /= 100;
        decimal_part[1] = floor((modf(latitude, &latitude) * 100) + 0.5); // 分
        latitude += (decimal_part[1] + decimal_part[0]) / 60;

        if (nmea_lines[3][0] == 'S')
            latitude = -latitude;

        decimal_part[0] = modf(strtof(nmea_lines[4], NULL), &longitude); // 秒
        longitude /= 100;
        decimal_part[1] = floor((modf(longitude, &longitude) * 100) + 0.5); // 分
        longitude += (decimal_part[1] + decimal_part[0]) / 60;

        if (nmea_lines[5][0] == 'W')
            longitude = -longitude;

        // 移動速度と移動方向はGGAではわからない

    }
}

// valid = 0
// invalid = other
uint8_t GPSDecoder::validate()
{
    uint8_t checksum = 0, nmea_checksum, flag = 0;
    char checksum_str[3] = {0};

    if (nmea_line[0] != '$') {
//        printf("invalid preamble %02X\n", nmea_line[0]);
        return 1;
    }

    for (int i = 1; i < strlen((char *)nmea_line); i++) {
        if (flag) {
            // 2byte checksum
            memcpy(checksum_str, (char *)nmea_line + i, 2);
            nmea_checksum = (uint8_t)strtol(checksum_str, NULL, 16);
            break;
        } else {
            if (nmea_line[i] == '*') {
                flag = 1;
                continue;
            }
            checksum = checksum ^ nmea_line[i];
        }
    }
    if (checksum != nmea_checksum) {
//        printf("invalid checksum\n");
        return 2;
    }
//    printf("validation passed\n");
    return 0;
}

long GPSDecoder::str2int(char *src_ptr, uint8_t len)
{
    char tmp[16] = {0};
    memcpy(tmp, src_ptr, len);
    return strtol(tmp, NULL, 10);
}

int GPSDecoder::split(char *str, const char delim, char *token[], int max_item)
{
    int cnt = 0;
    int len = strlen(str);

    token[cnt++] = str;
    for (int i = 0; i < len; i++) {
        if (str[i] == delim) {
            str[i] = '\0';
            if (cnt == max_item)
                return cnt;
            token[cnt++] = str + i + 1;
        }
    }

    return cnt;
}

time_t GPSDecoder::get_unixtime()
{
    struct tm t;
    t.tm_sec = sec;
    t.tm_min = min;
    t.tm_hour = hour;
    t.tm_mday = day;
    t.tm_mon = month - 1;
    t.tm_year = year - 1900;

    return mktime(&t);
}

void GPSDecoder::dump_info(char *buf)
{
    sprintf(buf, "%d/%02d/%02d %02d:%02d:%02d.%03d (UTC)\r\n", year, month, day, hour, min, sec, msec);
    sprintf(buf, "%slatitude: %f\r\n", buf, latitude);
    sprintf(buf, "%slongitude: %f\r\n", buf, longitude);
    sprintf(buf, "%sspeed %f km/h (%f knot)\r\n", buf, speed, speed / 1.852f);
    sprintf(buf, "%sdirection %f degree\r\n", buf, move_direction);
}