bool ConnectionGPS::ParseAnswer ( const string &  buffer )

inlineprivate

Definition at line 58 of file gpsctrl.cc.

References GPS::NEMA::count, Error(), GPS::NEMA::geosep, GPS::NEMA::hdop, GPS::NEMA::height, i, GPS::State::kDisabled, GPS::State::kEnabled, GPS::State::kLocked, GPS::NEMA::lat, GPS::NEMA::lng, GPS::NEMA::qos, Tools::Split(), and GPS::NEMA::time.

    {
        if (buffer=="Invalid command, type help")
        {
            Error("Command was ignored by GPS.");
            return false;
        }

        // answer to get_status or veto_[on|off|60]
        if (buffer=="veto_60" || buffer=="veto 60 now on")
        {
            if (fState!=GPS::State::kLocked)
                fState = GPS::State::kEnabled;
            PostMessage(string("get_nema\r\n"), 10);
            return true;
        }
        if (buffer=="veto_on" || buffer=="veto now on")
        {
            fState = GPS::State::kDisabled;
            PostMessage(string("get_nema\r\n"), 10);
            return true;
        }
        /*
        if (buffer=="veto_off" || buffer=="veto now off")
        {
            fState = GPS::State::kVetoOff;
            PostMessage(string("get_nema\r\n"), 10);
            return true;
        }*/

        // answer to get_nema
        if (buffer[0]=='$')
        {
            /*
             1    = UTC of Position
             2    = Latitude
             3    = N or S
             4    = Longitude
             5    = E or W
             6    = GPS quality indicator (0=invalid; 1=GPS fix;
                    2=Diff. GPS fix)
             7    = Number of satellites in use [not those in view]
             8    = Horizontal dilution of position
             9    = Antenna altitude above/below mean sea level (geoid)
             10   = Meters  (Antenna height unit)
             11   = Geoidal separation (Diff. between WGS-84 earth ellipsoid
                    and mean sea level.  -=geoid is below WGS-84 ellipsoid)
             12   = Meters  (Units of geoidal separation)
             13   = Age in seconds since last update from diff.
                    reference station
             14   = Diff. reference station ID#
             */

            const vector<string> cs = Tools::Split(buffer, "$*");
            if (cs.size()!=3)
                throw runtime_error("syntax error");

            // check checksum
            uint8_t c = cs[1][0];
            for (size_t i=1; i<cs[1].size(); i++)
                c ^= cs[1][i];

            stringstream ss;
            ss << std::hex << cs[2];

            unsigned int x;
            ss >> x;

            if (x!=c)
                throw runtime_error("checksum error");

            // interpret contents
            const vector<string> dat = Tools::Split(cs[1], ",");
            if (dat.size()!=15)
                throw runtime_error("size mismatch");
            if (dat[0]!="GPGGA")
                throw runtime_error("type mismatch");
            if (dat[5]!="W" && dat[5]!="E")
                throw runtime_error("longitude type unknown");
            if (dat[10]!="M")
                throw runtime_error("height unit unknown");
            if (dat[12]!="M")
                throw runtime_error("hdop unit unknown");
            if (!dat[13].empty())
                throw runtime_error("unexpected data at position 13");
            if (dat[14]!="0000")
                throw runtime_error("unexpected data at position 14");

            GPS::NEMA nema;
            nema.time   = ConvTm(dat[1]);
            nema.lat    = dat[3]=="N" ? ConvLngLat(dat[2]) : -ConvLngLat(dat[3]);
            nema.lng    = dat[5]=="W" ? ConvLngLat(dat[4]) : -ConvLngLat(dat[4]);
            nema.qos    = stoi(dat[6]);
            nema.count  = stoi(dat[7]);
            nema.hdop   = stof(dat[8]);
            nema.height = stof(dat[9]);
            nema.geosep = stof(dat[11]);

            if (fabs(nema.time-fmod(Time().Mjd(), 1))*24*3600>5)
            {
                Error("Time mismatch: GPS time deviates from PC time by more than 5s");
                return false;
            }

            if (fState>=GPS::State::kEnabled)
                fState = nema.qos==1 ? GPS::State::kLocked : GPS::State::kEnabled;

            Update(nema);

            return true;
        }

        return false;
    }

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