ardupilot/AntennaTracker/tracking.pde

/// -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*-

/**
  update_vehicle_position_estimate - updates estimate of vehicle positions
  should be called at 50hz
 */
static void update_vehicle_pos_estimate()
{
    // calculate time since last actual position update
    float dt = (hal.scheduler->micros() - vehicle.last_update_us) * 1.0e-6f;

    // if less than 5 seconds since last position update estimate the position
    if (dt < TRACKING_TIMEOUT_SEC) {
        // project the vehicle position to take account of lost radio packets
        vehicle.location_estimate = vehicle.location;
        location_update(vehicle.location_estimate, vehicle.heading, vehicle.ground_speed * dt);
        // set valid_location flag
        vehicle.location_valid = true;
    } else {
        // vehicle has been lost, set lost flag
        vehicle.location_valid = false;
    }
}

/**
  update_tracker_position - updates antenna tracker position from GPS location
  should be called at 50hz
 */
static void update_tracker_position()
{
    // update our position if we have at least a 2D fix
    // REVISIT: what if we lose lock during a mission and the antenna is moving?
    if (gps.status() >= AP_GPS::GPS_OK_FIX_2D) {
        current_loc = gps.location();
    }
}

/**
  update_bearing_and_distance - updates bearing and distance to the vehicle
  should be called at 50hz
 */
static void update_bearing_and_distance()
{
    // exit immediately if we do not have a valid vehicle position
    if (!vehicle.location_valid) {
        return;
    }

    // calculate bearing to vehicle
    // To-Do: remove need for check of control_mode
    if (control_mode != SCAN && !nav_status.manual_control_yaw) {
        nav_status.bearing  = get_bearing_cd(current_loc, vehicle.location_estimate) * 0.01f;
    }

    // calculate distance to vehicle
    nav_status.distance = get_distance(current_loc, vehicle.location_estimate);

    // calculate pitch to vehicle
    // To-Do: remove need for check of control_mode
    if (control_mode != SCAN && !nav_status.manual_control_pitch) {
        nav_status.pitch    = degrees(atan2f(nav_status.altitude_difference, nav_status.distance));
    }
}

/**
  main antenna tracking code, called at 50Hz
 */
static void update_tracking(void)
{
    // update vehicle position estimate
    update_vehicle_pos_estimate();

    // update antenna tracker position from GPS
    update_tracker_position();

    // update bearing and distance to vehicle
    update_bearing_and_distance();

    // do not perform any servo updates until startup delay has passed
    if (g.startup_delay > 0 &&
        hal.scheduler->millis() - start_time_ms < g.startup_delay*1000) {
        return;
    }

    switch (control_mode) {
    case AUTO:
        update_auto();
        break;

    case MANUAL:
        update_manual();
        break;

    case SCAN:
        update_scan();
        break;

    case STOP:
    case INITIALISING:
        break;
    }
}

/**
   handle an updated position from the aircraft
 */
static void tracking_update_position(const mavlink_global_position_int_t &msg)
{
    vehicle.location.lat = msg.lat;
    vehicle.location.lng = msg.lon;
    vehicle.location.alt = msg.alt/10;
    vehicle.heading      = msg.hdg * 0.01f;
    vehicle.ground_speed = pythagorous2(msg.vx, msg.vy) * 0.01f;
    vehicle.last_update_us = hal.scheduler->micros();    
    vehicle.last_update_ms = hal.scheduler->millis();
}


/**
   handle an updated pressure reading from the aircraft
 */
static void tracking_update_pressure(const mavlink_scaled_pressure_t &msg)
{
    float local_pressure = barometer.get_pressure();
    float aircraft_pressure = msg.press_abs*100.0f;

    // calculate altitude difference based on difference in barometric pressure
    float alt_diff = barometer.get_altitude_difference(local_pressure, aircraft_pressure);
    if (!isnan(alt_diff)) {
        nav_status.altitude_difference = alt_diff + nav_status.altitude_offset;
    }

    if (nav_status.need_altitude_calibration) {
        // we have done a baro calibration - zero the altitude
        // difference to the aircraft
        nav_status.altitude_offset = -nav_status.altitude_difference;
        nav_status.altitude_difference = 0;
        nav_status.need_altitude_calibration = false;
    }
}

/**
   handle a manual control message by using the data to command yaw and pitch
 */
static void tracking_manual_control(const mavlink_manual_control_t &msg)
{
    nav_status.bearing = msg.x;
    nav_status.pitch   = msg.y;
    nav_status.distance = 0.0;
    nav_status.manual_control_yaw   = (msg.x != 0x7FFF);
    nav_status.manual_control_pitch = (msg.y != 0x7FFF);
    // z, r and buttons are not used
}

/**
   update_armed_disarmed - set armed LED if we have received a position update within the last 5 seconds
 */
static void update_armed_disarmed()
{
    if (vehicle.last_update_ms != 0 && (hal.scheduler->millis() - vehicle.last_update_ms) < TRACKING_TIMEOUT_MS) {
        AP_Notify::flags.armed = true;
    } else {
        AP_Notify::flags.armed = false;
    }
}