flightgear/utils/GPSsmooth/UGear_main.cxx

#ifdef HAVE_CONFIG_H
#  include <config.h>
#endif

#ifndef _MSC_VER
#  include <strings.h>		// for bzero()
#else
#  define bzero(a,b) memset(a,0,b)
#endif
#include <iostream>
#include <string>

#include <plib/net.h>
#include <plib/sg.h>

#include <simgear/constants.h>
#include <simgear/io/lowlevel.hxx> // endian tests
#include <simgear/io/sg_file.hxx>
#include <simgear/serial/serial.hxx>
#include <simgear/math/sg_geodesy.hxx>
#include <simgear/timing/timestamp.hxx>

#include <Network/net_ctrls.hxx>
#include <Network/net_fdm.hxx>

#include "UGear.hxx"


SG_USING_STD(cout);
SG_USING_STD(endl);
SG_USING_STD(string);


// Network channels
static netSocket fdm_sock, ctrls_sock;

// ugear data
UGEARTrack track;

// Default ports
static int fdm_port = 5505;
static int ctrls_port = 5506;

// Default path
static string infile = "";
static string flight_dir = "";
static string serialdev = "";
static string outfile = "";

// Master time counter
float sim_time = 0.0f;
double frame_us = 0.0f;

// sim control
SGTimeStamp last_time_stamp;
SGTimeStamp current_time_stamp;

// altitude offset
double alt_offset = 0.0;

// skip initial seconds
double skip = 0.0;

// for speed estimate
// double last_lat = 0.0, last_lon = 0.0;
// double kts_filter = 0.0;

bool inited = false;

bool run_real_time = true;

bool ignore_checksum = false;

bool sg_swap = false;

bool est_controls = false;

// The function htond is defined this way due to the way some
// processors and OSes treat floating point values.  Some will raise
// an exception whenever a "bad" floating point value is loaded into a
// floating point register.  Solaris is notorious for this, but then
// so is LynxOS on the PowerPC.  By translating the data in place,
// there is no need to load a FP register with the "corruped" floating
// point value.  By doing the BIG_ENDIAN test, I can optimize the
// routine for big-endian processors so it can be as efficient as
// possible
static void htond (double &x)	
{
    if ( sgIsLittleEndian() ) {
        int    *Double_Overlay;
        int     Holding_Buffer;
    
        Double_Overlay = (int *) &x;
        Holding_Buffer = Double_Overlay [0];
    
        Double_Overlay [0] = htonl (Double_Overlay [1]);
        Double_Overlay [1] = htonl (Holding_Buffer);
    } else {
        return;
    }
}

// Float version
static void htonf (float &x)	
{
    if ( sgIsLittleEndian() ) {
        int    *Float_Overlay;
        int     Holding_Buffer;
    
        Float_Overlay = (int *) &x;
        Holding_Buffer = Float_Overlay [0];
    
        Float_Overlay [0] = htonl (Holding_Buffer);
    } else {
        return;
    }
}


static void ugear2fg( gps *gpspacket, imu *imupacket, nav *navpacket,
		      servo *servopacket, health *healthpacket,
		      FGNetFDM *fdm, FGNetCtrls *ctrls )
{
    unsigned int i;

    // Version sanity checking
    fdm->version = FG_NET_FDM_VERSION;

    // Aero parameters
    fdm->longitude = navpacket->lon * SG_DEGREES_TO_RADIANS;
    fdm->latitude = navpacket->lat * SG_DEGREES_TO_RADIANS;
    fdm->altitude = navpacket->alt + alt_offset;
    fdm->agl = -9999.0;
    fdm->psi = imupacket->psi; // heading
    fdm->phi = imupacket->phi; // roll
    fdm->theta = imupacket->the; // pitch;

    fdm->phidot = 0.0;
    fdm->thetadot = 0.0;
    fdm->psidot = 0.0;

    // estimate speed
    // double az1, az2, dist;
    // geo_inverse_wgs_84( pos.altitude_msl, last_lat, last_lon,
    //                     pos.lat_deg, pos.lon_deg, &az1, &az2, &dist );
    // double v_ms = dist / (frame_us / 1000000);
    // double v_kts = v_ms * SG_METER_TO_NM * 3600;
    // kts_filter = (0.99 * kts_filter) + (0.01 * v_kts);
    double vn = navpacket->vn;
    double ve = navpacket->ve;
    double vd = navpacket->vd;

    // enable to use ground track heading
    // fdm->psi = SGD_PI * 0.5 - atan2(vn, ve); // heading

    fdm->vcas = sqrt( vn*vn + ve*ve + vd*vd );
    // last_lat = pos.lat_deg;
    // last_lon = pos.lon_deg;
    // cout << "kts_filter = " << kts_filter << " vel = " << pos.speed_kts << endl;

    fdm->climb_rate = 0; // fps
    // cout << "climb rate = " << aero->hdota << endl;
    fdm->v_north = 0.0;
    fdm->v_east = 0.0;
    fdm->v_down = 0.0;
    fdm->v_wind_body_north = 0.0;
    fdm->v_wind_body_east = 0.0;
    fdm->v_wind_body_down = 0.0;
    fdm->stall_warning = 0.0;

    fdm->A_X_pilot = 0.0;
    fdm->A_Y_pilot = 0.0;
    fdm->A_Z_pilot = 0.0 /* (should be -G) */;

    // Engine parameters
    fdm->num_engines = 1;
    fdm->eng_state[0] = 2;
    // cout << "state = " << fdm->eng_state[0] << endl;
    double rpm = 5000.0 - ((double)servopacket->chn[2] / 65536.0)*3500.0;
    if ( rpm < 0.0 ) { rpm = 0.0; }
    if ( rpm > 5000.0 ) { rpm = 5000.0; }
    fdm->rpm[0] = rpm;

    fdm->fuel_flow[0] = 0.0;
    fdm->egt[0] = 0.0;
    // cout << "egt = " << aero->EGT << endl;
    fdm->oil_temp[0] = 0.0;
    fdm->oil_px[0] = 0.0;

    // Consumables
    fdm->num_tanks = 2;
    fdm->fuel_quantity[0] = 0.0;
    fdm->fuel_quantity[1] = 0.0;

    // Gear and flaps
    fdm->num_wheels = 3;
    fdm->wow[0] = 0;
    fdm->wow[1] = 0;
    fdm->wow[2] = 0;

    // the following really aren't used in this context
    fdm->cur_time = 0;
    fdm->warp = 0;
    fdm->visibility = 0;

    // cout << "Flap deflection = " << aero->dflap << endl;
    fdm->left_flap = 0.0;
    fdm->right_flap = 0.0;

    if ( est_controls ) {
        static float est_elev = 0.0;
        static float est_aileron = 0.0;
        static float est_rudder = 0.0;
        est_elev = 0.95 * est_elev + 0.05 * (imupacket->q * 8);
        est_aileron = 0.95 * est_aileron + 0.05 * (imupacket->p * 8);
        est_rudder = 0.95 * est_rudder + 0.05 * (imupacket->r * 8);
        fdm->elevator = -est_elev;
        fdm->left_aileron = est_aileron;
        fdm->right_aileron = -est_aileron;
        fdm->rudder = est_rudder;
    } else {
        fdm->elevator = ((double)servopacket->chn[1] / 32768.0) - 1.0;
        fdm->left_aileron = ((double)servopacket->chn[0] / 32768.0) - 1.0;
        fdm->right_aileron = 1.0 - ((double)servopacket->chn[0] / 32768.0);
        fdm->rudder = 1.0 - ((double)servopacket->chn[3] / 32768.0);
    }
    fdm->elevator_trim_tab = 0.0;
    fdm->left_flap = 0.0;
    fdm->right_flap = 0.0;
    fdm->nose_wheel = 0.0;
    fdm->speedbrake = 0.0;
    fdm->spoilers = 0.0;

    // Convert the net buffer to network format
    fdm->version = htonl(fdm->version);

    htond(fdm->longitude);
    htond(fdm->latitude);
    htond(fdm->altitude);
    htonf(fdm->agl);
    htonf(fdm->phi);
    htonf(fdm->theta);
    htonf(fdm->psi);
    htonf(fdm->alpha);
    htonf(fdm->beta);

    htonf(fdm->phidot);
    htonf(fdm->thetadot);
    htonf(fdm->psidot);
    htonf(fdm->vcas);
    htonf(fdm->climb_rate);
    htonf(fdm->v_north);
    htonf(fdm->v_east);
    htonf(fdm->v_down);
    htonf(fdm->v_wind_body_north);
    htonf(fdm->v_wind_body_east);
    htonf(fdm->v_wind_body_down);

    htonf(fdm->A_X_pilot);
    htonf(fdm->A_Y_pilot);
    htonf(fdm->A_Z_pilot);

    htonf(fdm->stall_warning);
    htonf(fdm->slip_deg);

    for ( i = 0; i < fdm->num_engines; ++i ) {
        fdm->eng_state[i] = htonl(fdm->eng_state[i]);
        htonf(fdm->rpm[i]);
        htonf(fdm->fuel_flow[i]);
        htonf(fdm->egt[i]);
        htonf(fdm->cht[i]);
        htonf(fdm->mp_osi[i]);
        htonf(fdm->tit[i]);
        htonf(fdm->oil_temp[i]);
        htonf(fdm->oil_px[i]);
    }
    fdm->num_engines = htonl(fdm->num_engines);

    for ( i = 0; i < fdm->num_tanks; ++i ) {
        htonf(fdm->fuel_quantity[i]);
    }
    fdm->num_tanks = htonl(fdm->num_tanks);

    for ( i = 0; i < fdm->num_wheels; ++i ) {
        fdm->wow[i] = htonl(fdm->wow[i]);
        htonf(fdm->gear_pos[i]);
        htonf(fdm->gear_steer[i]);
        htonf(fdm->gear_compression[i]);
    }
    fdm->num_wheels = htonl(fdm->num_wheels);

    fdm->cur_time = htonl( fdm->cur_time );
    fdm->warp = htonl( fdm->warp );
    htonf(fdm->visibility);

    htonf(fdm->elevator);
    htonf(fdm->elevator_trim_tab);
    htonf(fdm->left_flap);
    htonf(fdm->right_flap);
    htonf(fdm->left_aileron);
    htonf(fdm->right_aileron);
    htonf(fdm->rudder);
    htonf(fdm->nose_wheel);
    htonf(fdm->speedbrake);
    htonf(fdm->spoilers);


}


static void send_data( gps *gpspacket, imu *imupacket, nav *navpacket,
		       servo *servopacket, health *healthpacket ) {
    int len;
    int fdmsize = sizeof( FGNetFDM );

    // cout << "Running main loop" << endl;

    FGNetFDM fgfdm;
    FGNetCtrls fgctrls;

    ugear2fg( gpspacket, imupacket, navpacket, servopacket, healthpacket,
	      &fgfdm, &fgctrls );
    len = fdm_sock.send(&fgfdm, fdmsize, 0);
}


void usage( const string &argv0 ) {
    cout << "Usage: " << argv0 << endl;
    cout << "\t[ --help ]" << endl;
    cout << "\t[ --infile <infile_name>" << endl;
    cout << "\t[ --flight <flight_dir>" << endl;
    cout << "\t[ --serial <dev_name>" << endl;
    cout << "\t[ --outfile <outfile_name> (capture the data to a file)" << endl;
    cout << "\t[ --hertz <hertz> ]" << endl;
    cout << "\t[ --host <hostname> ]" << endl;
    cout << "\t[ --broadcast ]" << endl;
    cout << "\t[ --fdm-port <fdm output port #> ]" << endl;
    cout << "\t[ --ctrls-port <ctrls output port #> ]" << endl;
    cout << "\t[ --estimate-control-deflections ]" << endl;
    cout << "\t[ --altitude-offset <meters> ]" << endl;
    cout << "\t[ --skip-seconds <seconds> ]" << endl;
    cout << "\t[ --no-real-time ]" << endl;
    cout << "\t[ --ignore-checksum ]" << endl;
    cout << "\t[ --sg-swap ]" << endl;
}


int main( int argc, char **argv ) {
    double hertz = 60.0;
    string out_host = "localhost";
    bool do_broadcast = false;

    // process command line arguments
    for ( int i = 1; i < argc; ++i ) {
        if ( strcmp( argv[i], "--help" ) == 0 ) {
            usage( argv[0] );
            exit( 0 );
        } else if ( strcmp( argv[i], "--hertz" ) == 0 ) {
            ++i;
            if ( i < argc ) {
                hertz = atof( argv[i] );
            } else {
                usage( argv[0] );
                exit( -1 );
            }
        } else if ( strcmp( argv[i], "--infile" ) == 0 ) {
            ++i;
            if ( i < argc ) {
                infile = argv[i];
            } else {
                usage( argv[0] );
                exit( -1 );
            }
        } else if ( strcmp( argv[i], "--flight" ) == 0 ) {
            ++i;
            if ( i < argc ) {
                flight_dir = argv[i];
            } else {
                usage( argv[0] );
                exit( -1 );
            }
        } else if ( strcmp( argv[i], "--outfile" ) == 0 ) {
            ++i;
            if ( i < argc ) {
                outfile = argv[i];
            } else {
                usage( argv[0] );
                exit( -1 );
            }
        } else if ( strcmp( argv[i], "--serial" ) == 0 ) {
            ++i;
            if ( i < argc ) {
                serialdev = argv[i];
            } else {
                usage( argv[0] );
                exit( -1 );
            }
        } else if ( strcmp( argv[i], "--host" ) == 0 ) {
            ++i;
            if ( i < argc ) {
                out_host = argv[i];
            } else {
                usage( argv[0] );
                exit( -1 );
            }
        } else if ( strcmp( argv[i], "--broadcast" ) == 0 ) {
	  do_broadcast = true;
        } else if ( strcmp( argv[i], "--fdm-port" ) == 0 ) {
            ++i;
            if ( i < argc ) {
                fdm_port = atoi( argv[i] );
            } else {
                usage( argv[0] );
                exit( -1 );
            }
        } else if ( strcmp( argv[i], "--ctrls-port" ) == 0 ) {
            ++i;
            if ( i < argc ) {
                ctrls_port = atoi( argv[i] );
            } else {
                usage( argv[0] );
                exit( -1 );
            }
        } else if ( strcmp (argv[i], "--estimate-control-deflections" ) == 0 ) {
            est_controls = true;
        } else if ( strcmp( argv[i], "--altitude-offset" ) == 0 ) {
            ++i;
            if ( i < argc ) {
                alt_offset = atof( argv[i] );
            } else {
                usage( argv[0] );
                exit( -1 );
            }
        } else if ( strcmp( argv[i], "--skip-seconds" ) == 0 ) {
            ++i;
            if ( i < argc ) {
                skip = atof( argv[i] );
            } else {
                usage( argv[0] );
                exit( -1 );
            }
	} else if ( strcmp( argv[i], "--no-real-time" ) == 0 ) {
            run_real_time = false;
	} else if ( strcmp( argv[i], "--ignore-checksum" ) == 0 ) {
            ignore_checksum = true;
	} else if ( strcmp( argv[i], "--sg-swap" ) == 0 ) {
            sg_swap = true;
        } else {
            usage( argv[0] );
            exit( -1 );
        }
    }

    // Setup up outgoing network connections

    netInit( &argc,argv ); // We must call this before any other net stuff

    if ( ! fdm_sock.open( false ) ) {  // open a UDP socket
        cout << "error opening fdm output socket" << endl;
        return -1;
    }
    if ( ! ctrls_sock.open( false ) ) {  // open a UDP socket
        cout << "error opening ctrls output socket" << endl;
        return -1;
    }
    cout << "open net channels" << endl;

    fdm_sock.setBlocking( false );
    ctrls_sock.setBlocking( false );
    cout << "blocking false" << endl;

    if ( do_broadcast ) {
        fdm_sock.setBroadcast( true );
        ctrls_sock.setBroadcast( true );
    }

    if ( fdm_sock.connect( out_host.c_str(), fdm_port ) == -1 ) {
        perror("connect");
        cout << "error connecting to outgoing fdm port: " << out_host
	     << ":" << fdm_port << endl;
        return -1;
    }
    cout << "connected outgoing fdm socket" << endl;

    if ( ctrls_sock.connect( out_host.c_str(), ctrls_port ) == -1 ) {
        perror("connect");
        cout << "error connecting to outgoing ctrls port: " << out_host
	     << ":" << ctrls_port << endl;
        return -1;
    }
    cout << "connected outgoing ctrls socket" << endl;

    if ( sg_swap ) {
        track.set_stargate_swap_mode();
    }

    if ( infile.length() || flight_dir.length() ) {
        if ( infile.length() ) {
            // Load data from a stream log data file
            track.load_stream( infile, ignore_checksum );
        } else if ( flight_dir.length() ) {
            // Load data from a flight directory
            track.load_flight( flight_dir );
        }
        cout << "Loaded " << track.gps_size() << " gps records." << endl;
        cout << "Loaded " << track.imu_size() << " imu records." << endl;
        cout << "Loaded " << track.nav_size() << " nav records." << endl;
        cout << "Loaded " << track.servo_size() << " servo records." << endl;
        cout << "Loaded " << track.health_size() << " health records." << endl;

        int size = track.imu_size();

        double current_time = track.get_imupt(0).time;
        cout << "Track begin time is " << current_time << endl;
        double end_time = track.get_imupt(size-1).time;
        cout << "Track end time is " << end_time << endl;
        cout << "Duration = " << end_time - current_time << endl;

        // advance skip seconds forward
        current_time += skip;

        frame_us = 1000000.0 / hertz;
        if ( frame_us < 0.0 ) {
            frame_us = 0.0;
        }

        SGTimeStamp start_time;
        start_time.stamp();
        int gps_count = 0;
        int imu_count = 0;
        int nav_count = 0;
        int servo_count = 0;
        int health_count = 0;

        gps gps0, gps1;
        gps0 = gps1 = track.get_gpspt( 0 );
    
        imu imu0, imu1;
        imu0 = imu1 = track.get_imupt( 0 );
    
        nav nav0, nav1;
        nav0 = nav1 = track.get_navpt( 0 );
    
        servo servo0, servo1;
        servo0 = servo1 = track.get_servopt( 0 );
    
        health health0, health1;
        health0 = health1 = track.get_healthpt( 0 );

        double last_lat = -999.9, last_lon = -999.9;

        printf("<gpx>\n");
        printf(" <trk>\n");
        printf("  <trkseg>\n");
        while ( current_time < end_time ) {
            // cout << "current_time = " << current_time << " end_time = "
            //      << end_time << endl;

            // Advance gps pointer
            while ( current_time > gps1.time
                    && gps_count < track.gps_size() - 1 )
            {
                gps0 = gps1;
                ++gps_count;
                // cout << "count = " << count << endl;
                gps1 = track.get_gpspt( gps_count );
            }
            // cout << "p0 = " << p0.get_time() << " p1 = " << p1.get_time()
            //      << endl;

            // Advance imu pointer
            while ( current_time > imu1.time
                    && imu_count < track.imu_size() - 1 )
            {
                imu0 = imu1;
                ++imu_count;
                // cout << "count = " << count << endl;
                imu1 = track.get_imupt( imu_count );
            }
            //  cout << "pos0 = " << pos0.get_seconds()
            // << " pos1 = " << pos1.get_seconds() << endl;

            // Advance nav pointer
            while ( current_time > nav1.time
                    && nav_count < track.nav_size() - 1 )
            {
                nav0 = nav1;
                ++nav_count;
                // cout << "nav count = " << nav_count << endl;
                nav1 = track.get_navpt( nav_count );
            }
            //  cout << "pos0 = " << pos0.get_seconds()
            // << " pos1 = " << pos1.get_seconds() << endl;

            // Advance servo pointer
            while ( current_time > servo1.time
                    && servo_count < track.servo_size() - 1 )
            {
                servo0 = servo1;
                ++servo_count;
                // cout << "count = " << count << endl;
                servo1 = track.get_servopt( servo_count );
            }
            //  cout << "pos0 = " << pos0.get_seconds()
            // << " pos1 = " << pos1.get_seconds() << endl;

            // Advance health pointer
            while ( current_time > health1.time
                    && health_count < track.health_size() - 1 )
            {
                health0 = health1;
                ++health_count;
                // cout << "count = " << count << endl;
                health1 = track.get_healthpt( health_count );
            }
            //  cout << "pos0 = " << pos0.get_seconds()
            // << " pos1 = " << pos1.get_seconds() << endl;

            double gps_percent;
            if ( fabs(gps1.time - gps0.time) < 0.00001 ) {
                gps_percent = 0.0;
            } else {
                gps_percent =
                    (current_time - gps0.time) /
                    (gps1.time - gps0.time);
            }
            // cout << "Percent = " << percent << endl;

            double imu_percent;
            if ( fabs(imu1.time - imu0.time) < 0.00001 ) {
                imu_percent = 0.0;
            } else {
                imu_percent =
                    (current_time - imu0.time) /
                    (imu1.time - imu0.time);
            }
            // cout << "Percent = " << percent << endl;

            double nav_percent;
            if ( fabs(nav1.time - nav0.time) < 0.00001 ) {
                nav_percent = 0.0;
            } else {
                nav_percent =
                    (current_time - nav0.time) /
                    (nav1.time - nav0.time);
            }
            // cout << "Percent = " << percent << endl;

            double servo_percent;
            if ( fabs(servo1.time - servo0.time) < 0.00001 ) {
                servo_percent = 0.0;
            } else {
                servo_percent =
                    (current_time - servo0.time) /
                    (servo1.time - servo0.time);
            }
            // cout << "Percent = " << percent << endl;

            double health_percent;
            if ( fabs(health1.time - health0.time) < 0.00001 ) {
                health_percent = 0.0;
            } else {
                health_percent =
                    (current_time - health0.time) /
                    (health1.time - health0.time);
            }
            // cout << "Percent = " << percent << endl;

            gps gpspacket = UGEARInterpGPS( gps0, gps1, gps_percent );
            imu imupacket = UGEARInterpIMU( imu0, imu1, imu_percent );
            nav navpacket = UGEARInterpNAV( nav0, nav1, nav_percent );
            servo servopacket = UGEARInterpSERVO( servo0, servo1,
						  servo_percent );
            health healthpacket = UGEARInterpHEALTH( health0, health1,
						  health_percent );

            // cout << current_time << " " << p0.lat_deg << ", " << p0.lon_deg
            //      << endl;
            // cout << current_time << " " << p1.lat_deg << ", " << p1.lon_deg
            //      << endl;
            // cout << (double)current_time << " " << pos.lat_deg << ", "
            //      << pos.lon_deg << " " << att.yaw_deg << endl;
            if ( gpspacket.lat > -500 ) {
                // printf( "%.3f  %.4f %.4f %.1f  %.2f %.2f %.2f\n",
                //         current_time,
                //         navpacket.lat, navpacket.lon, navpacket.alt,
                //         imupacket.psi, imupacket.the, imupacket.phi );
                double dlat = last_lat - navpacket.lat;
                double dlon = last_lon - navpacket.lon;
                double dist = sqrt( dlat*dlat + dlon*dlon );
                if ( dist > 0.01 ) {
                    printf("   <trkpt lat=\"%.8f\" lon=\"%.8f\"></trkpt>\n",
                           navpacket.lat, navpacket.lon );
                    // printf(" </wpt>\n");
                    last_lat = navpacket.lat;
                    last_lon = navpacket.lon;
                }
	    }

            send_data( &gpspacket, &imupacket, &navpacket, &servopacket,
		       &healthpacket );

            if ( run_real_time ) {
                // Update the elapsed time.
                static bool first_time = true;
                if ( first_time ) {
                    last_time_stamp.stamp();
                    first_time = false;
                }

                current_time_stamp.stamp();
                /* Convert to ms */
                double elapsed_us = current_time_stamp - last_time_stamp;
                if ( elapsed_us < (frame_us - 2000) ) {
                    double requested_us = (frame_us - elapsed_us) - 2000 ;
                    ulMilliSecondSleep ( (int)(requested_us / 1000.0) ) ;
                }
                current_time_stamp.stamp();
                while ( current_time_stamp - last_time_stamp < frame_us ) {
                    current_time_stamp.stamp();
                }
            }

            current_time += (frame_us / 1000000.0);
            last_time_stamp = current_time_stamp;
        }

        printf("   <trkpt lat=\"%.8f\" lon=\"%.8f\"></trkpt>\n",
               nav1.lat, nav1.lon );

        printf("  </trkseg>\n");
        printf(" </trk>\n");
        nav0 = track.get_navpt( 0 );
        nav1 = track.get_navpt( track.nav_size() - 1 );
        printf(" <wpt lat=\"%.8f\" lon=\"%.8f\"></wpt>\n",
               nav0.lat, nav0.lon );
        printf(" <wpt lat=\"%.8f\" lon=\"%.8f\"></wpt>\n",
               nav1.lat, nav1.lon );
        printf("<gpx>\n");

        cout << "Processed " << imu_count << " entries in "
             << (current_time_stamp - start_time) / 1000000 << " seconds."
             << endl;
    } else if ( serialdev.length() ) {
        // process incoming data from the serial port

        int count = 0;
        double current_time = 0.0;
        double last_time = 0.0;

        gps gpspacket; bzero( &gpspacket, sizeof(gpspacket) );
	imu imupacket; bzero( &imupacket, sizeof(imupacket) );
	nav navpacket; bzero( &navpacket, sizeof(navpacket) );
	servo servopacket; bzero( &servopacket, sizeof(servopacket) );
	health healthpacket; bzero( &healthpacket, sizeof(healthpacket) );

        double gps_time = 0;
        double imu_time = 0;
        double nav_time = 0;
        double servo_time = 0;
        double health_time = 0;

        // open the serial port device
        SGSerialPort input( serialdev, 115200 );
        if ( !input.is_enabled() ) {
            cout << "Cannot open: " << serialdev << endl;
            return false;
        }

        // open up the data log file if requested
        if ( !outfile.length() ) {
            cout << "no --outfile <name> specified, cannot capture data!"
                 << endl;
            return false;
        }
        SGFile output( outfile );
        if ( !output.open( SG_IO_OUT ) ) {
            cout << "Cannot open: " << outfile << endl;
            return false;
        }

        while ( input.is_enabled() ) {
	    // cout << "looking for next message ..." << endl;
            int id = track.next_message( &input, &output, &gpspacket,
					 &imupacket, &navpacket, &servopacket,
					 &healthpacket, ignore_checksum );
            // cout << "message id = " << id << endl;
            count++;

            if ( id == GPS_PACKET ) {
                if ( gpspacket.time > gps_time ) {
                    gps_time = gpspacket.time;
                    current_time = gps_time;
                } else {
		  cout << "oops gps back in time: " << gpspacket.time << " " << gps_time << endl;
                }
	    } else if ( id == IMU_PACKET ) {
                if ( imupacket.time > imu_time ) {
                    imu_time = imupacket.time;
                    current_time = imu_time;
                } else {
                    cout << "oops imu back in time: " << imupacket.time << " " << imu_time << endl;
                }
	    } else if ( id == NAV_PACKET ) {
                if ( navpacket.time > nav_time ) {
                    nav_time = navpacket.time;
                    current_time = nav_time;
                } else {
                    cout << "oops nav back in time: " << navpacket.time << " " << nav_time << endl;
                }
	    } else if ( id == SERVO_PACKET ) {
                if ( servopacket.time > servo_time ) {
                    servo_time = servopacket.time;
                    current_time = servo_time;
                } else {
                    cout << "oops servo back in time: " << servopacket.time << " " << servo_time << endl;
                }
	    } else if ( id == HEALTH_PACKET ) {
                if ( healthpacket.time > health_time ) {
                    health_time = healthpacket.time;
                    current_time = health_time;
                } else {
                    cout << "oops health back in time: " << healthpacket.time << " " << health_time << endl;
                }
            }

            if ( current_time >= last_time + (1/hertz) ) {
                // if ( gpspacket.lat > -500 ) {
                printf( "%.2f  %.6f %.6f %.1f  %.2f %.2f %.2f  %.2f %d\n",
                        current_time,
                        navpacket.lat, navpacket.lon, navpacket.alt,
                        imupacket.phi*SGD_RADIANS_TO_DEGREES,
                        imupacket.the*SGD_RADIANS_TO_DEGREES,
                        imupacket.psi*SGD_RADIANS_TO_DEGREES,
                        healthpacket.volts,
                        healthpacket.est_seconds);
                // }

                last_time = current_time;
                send_data( &gpspacket, &imupacket, &navpacket, &servopacket,
                           &healthpacket );
            }
        }
    }

    return 0;
}