GCS_Mavlink.cpp

#include "GCS_Mavlink.h"

#include "Tracker.h"

// default sensors are present and healthy: gyro, accelerometer, barometer, rate_control, attitude_stabilization, yaw_position, altitude control, x/y position control, motor_control
#define MAVLINK_SENSOR_PRESENT_DEFAULT (MAV_SYS_STATUS_SENSOR_3D_GYRO | MAV_SYS_STATUS_SENSOR_3D_ACCEL | MAV_SYS_STATUS_SENSOR_ABSOLUTE_PRESSURE | MAV_SYS_STATUS_SENSOR_ANGULAR_RATE_CONTROL | MAV_SYS_STATUS_SENSOR_ATTITUDE_STABILIZATION | MAV_SYS_STATUS_SENSOR_YAW_POSITION | MAV_SYS_STATUS_SENSOR_Z_ALTITUDE_CONTROL | MAV_SYS_STATUS_SENSOR_XY_POSITION_CONTROL | MAV_SYS_STATUS_SENSOR_MOTOR_OUTPUTS)

/*
 *  !!NOTE!!
 *
 *  the use of NOINLINE separate functions for each message type avoids
 *  a compiler bug in gcc that would cause it to use far more stack
 *  space than is needed. Without the NOINLINE we use the sum of the
 *  stack needed for each message type. Please be careful to follow the
 *  pattern below when adding any new messages
 */

void Tracker::send_heartbeat(mavlink_channel_t chan)
{
    uint8_t base_mode = MAV_MODE_FLAG_CUSTOM_MODE_ENABLED;
    uint8_t system_status = MAV_STATE_ACTIVE;
    uint32_t custom_mode = control_mode;

    // work out the base_mode. This value is not very useful
    // for APM, but we calculate it as best we can so a generic
    // MAVLink enabled ground station can work out something about
    // what the MAV is up to. The actual bit values are highly
    // ambiguous for most of the APM flight modes. In practice, you
    // only get useful information from the custom_mode, which maps to
    // the APM flight mode and has a well defined meaning in the
    // ArduPlane documentation
    switch (control_mode) {
    case MANUAL:
        base_mode |= MAV_MODE_FLAG_MANUAL_INPUT_ENABLED;
        break;

    case STOP:
        break;

    case SCAN:
    case SERVO_TEST:
    case AUTO:
        base_mode |= MAV_MODE_FLAG_GUIDED_ENABLED |
            MAV_MODE_FLAG_STABILIZE_ENABLED;
        // note that MAV_MODE_FLAG_AUTO_ENABLED does not match what
        // APM does in any mode, as that is defined as "system finds its own goal
        // positions", which APM does not currently do
        break;

    case INITIALISING:
        system_status = MAV_STATE_CALIBRATING;
        break;
    }

    // we are armed if safety switch is not disarmed
    if (hal.util->safety_switch_state() != AP_HAL::Util::SAFETY_DISARMED) {
        base_mode |= MAV_MODE_FLAG_SAFETY_ARMED;
    }

    gcs().chan(chan-MAVLINK_COMM_0).send_heartbeat(MAV_TYPE_ANTENNA_TRACKER,
                                            base_mode,
                                            custom_mode,
                                            system_status);
}

void Tracker::send_attitude(mavlink_channel_t chan)
{
    Vector3f omega = ahrs.get_gyro();
    mavlink_msg_attitude_send(
        chan,
        AP_HAL::millis(),
        ahrs.roll,
        ahrs.pitch,
        ahrs.yaw,
        omega.x,
        omega.y,
        omega.z);
}


void Tracker::send_extended_status1(mavlink_channel_t chan)
{
    int16_t battery_current = -1;
    int8_t battery_remaining = -1;

    if (battery.has_current() && battery.healthy()) {
        battery_remaining = battery.capacity_remaining_pct();
        battery_current = battery.current_amps() * 100;
    }

    mavlink_msg_sys_status_send(
        chan,
        0,
        0,
        0,
        static_cast<uint16_t>(scheduler.load_average() * 1000),
        battery.voltage() * 1000,  // mV
        battery_current,        // in 10mA units
        battery_remaining,      // in %
        0,  // comm drops %,
        0,  // comm drops in pkts,
        0, 0, 0, 0);
}

void Tracker::send_location(mavlink_channel_t chan)
{
    uint32_t fix_time;
    if (gps.status() >= AP_GPS::GPS_OK_FIX_2D) {
        fix_time = gps.last_fix_time_ms();
    } else {
        fix_time = AP_HAL::millis();
    }
    const Vector3f &vel = gps.velocity();
    mavlink_msg_global_position_int_send(
        chan,
        fix_time,
        current_loc.lat,                // in 1E7 degrees
        current_loc.lng,                // in 1E7 degrees
        current_loc.alt * 10,        // millimeters above sea level
        0,
        vel.x * 100,  // X speed cm/s (+ve North)
        vel.y * 100,  // Y speed cm/s (+ve East)
        vel.z * 100,  // Z speed cm/s (+ve Down)
        ahrs.yaw_sensor);
}

void Tracker::send_nav_controller_output(mavlink_channel_t chan)
{
	float alt_diff = (g.alt_source == ALT_SOURCE_BARO) ? nav_status.alt_difference_baro : nav_status.alt_difference_gps;

    mavlink_msg_nav_controller_output_send(
        chan,
        0,
        nav_status.pitch,
        nav_status.bearing,
        nav_status.bearing,
        MIN(nav_status.distance, UINT16_MAX),
        alt_diff,
        0,
        0);
}


// report simulator state
void Tracker::send_simstate(mavlink_channel_t chan)
{
#if CONFIG_HAL_BOARD == HAL_BOARD_SITL
    sitl.simstate_send(chan);
#endif
}

bool GCS_MAVLINK_Tracker::handle_guided_request(AP_Mission::Mission_Command&)
{
    // do nothing
    return false;
}

void GCS_MAVLINK_Tracker::handle_change_alt_request(AP_Mission::Mission_Command&)
{
    // do nothing
}

// try to send a message, return false if it won't fit in the serial tx buffer
bool GCS_MAVLINK_Tracker::try_send_message(enum ap_message id)
{
    switch (id) {
    case MSG_HEARTBEAT:
        CHECK_PAYLOAD_SIZE(HEARTBEAT);
        last_heartbeat_time = AP_HAL::millis();
        tracker.send_heartbeat(chan);
        return true;

    case MSG_ATTITUDE:
        CHECK_PAYLOAD_SIZE(ATTITUDE);
        tracker.send_attitude(chan);
        break;

    case MSG_LOCATION:
        CHECK_PAYLOAD_SIZE(GLOBAL_POSITION_INT);
        tracker.send_location(chan);
        break;

    case MSG_NAV_CONTROLLER_OUTPUT:
        CHECK_PAYLOAD_SIZE(NAV_CONTROLLER_OUTPUT);
        tracker.send_nav_controller_output(chan);
        break;

    case MSG_RADIO_IN:
        CHECK_PAYLOAD_SIZE(RC_CHANNELS);
        send_radio_in(0);
        break;

    case MSG_SERVO_OUTPUT_RAW:
        CHECK_PAYLOAD_SIZE(SERVO_OUTPUT_RAW);
        send_servo_output_raw(false);
        break;

    case MSG_RAW_IMU1:
        CHECK_PAYLOAD_SIZE(RAW_IMU);
        send_raw_imu(tracker.ins, tracker.compass);
        break;

    case MSG_RAW_IMU2:
        CHECK_PAYLOAD_SIZE(SCALED_PRESSURE);
        send_scaled_pressure();
        break;

    case MSG_RAW_IMU3:
        CHECK_PAYLOAD_SIZE(SENSOR_OFFSETS);
        send_sensor_offsets(tracker.ins, tracker.compass);
        break;

    case MSG_SIMSTATE:
        CHECK_PAYLOAD_SIZE(SIMSTATE);
        tracker.send_simstate(chan);
        break;

    case MSG_EXTENDED_STATUS1:
        CHECK_PAYLOAD_SIZE(SYS_STATUS);
        tracker.send_extended_status1(chan);
        break;

    default:
        return GCS_MAVLINK::try_send_message(id);
    }
    return true;
}


/*
  default stream rates to 1Hz
 */
const AP_Param::GroupInfo GCS_MAVLINK::var_info[] = {
    // @Param: RAW_SENS
    // @DisplayName: Raw sensor stream rate
    // @Description: Raw sensor stream rate to ground station
    // @Units: Hz
    // @Range: 0 10
    // @Increment: 1
    // @User: Advanced
    AP_GROUPINFO("RAW_SENS", 0, GCS_MAVLINK, streamRates[0],  1),

    // @Param: EXT_STAT
    // @DisplayName: Extended status stream rate to ground station
    // @Description: Extended status stream rate to ground station
    // @Units: Hz
    // @Range: 0 10
    // @Increment: 1
    // @User: Advanced
    AP_GROUPINFO("EXT_STAT", 1, GCS_MAVLINK, streamRates[1],  1),

    // @Param: RC_CHAN
    // @DisplayName: RC Channel stream rate to ground station
    // @Description: RC Channel stream rate to ground station
    // @Units: Hz
    // @Range: 0 10
    // @Increment: 1
    // @User: Advanced
    AP_GROUPINFO("RC_CHAN",  2, GCS_MAVLINK, streamRates[2],  1),

    // @Param: RAW_CTRL
    // @DisplayName: Raw Control stream rate to ground station
    // @Description: Raw Control stream rate to ground station
    // @Units: Hz
    // @Range: 0 10
    // @Increment: 1
    // @User: Advanced
    AP_GROUPINFO("RAW_CTRL", 3, GCS_MAVLINK, streamRates[3],  1),

    // @Param: POSITION
    // @DisplayName: Position stream rate to ground station
    // @Description: Position stream rate to ground station
    // @Units: Hz
    // @Range: 0 10
    // @Increment: 1
    // @User: Advanced
    AP_GROUPINFO("POSITION", 4, GCS_MAVLINK, streamRates[4],  1),

    // @Param: EXTRA1
    // @DisplayName: Extra data type 1 stream rate to ground station
    // @Description: Extra data type 1 stream rate to ground station
    // @Units: Hz
    // @Range: 0 10
    // @Increment: 1
    // @User: Advanced
    AP_GROUPINFO("EXTRA1",   5, GCS_MAVLINK, streamRates[5],  1),

    // @Param: EXTRA2
    // @DisplayName: Extra data type 2 stream rate to ground station
    // @Description: Extra data type 2 stream rate to ground station
    // @Units: Hz
    // @Range: 0 10
    // @Increment: 1
    // @User: Advanced
    AP_GROUPINFO("EXTRA2",   6, GCS_MAVLINK, streamRates[6],  1),

    // @Param: EXTRA3
    // @DisplayName: Extra data type 3 stream rate to ground station
    // @Description: Extra data type 3 stream rate to ground station
    // @Units: Hz
    // @Range: 0 10
    // @Increment: 1
    // @User: Advanced
    AP_GROUPINFO("EXTRA3",   7, GCS_MAVLINK, streamRates[7],  1),

    // @Param: PARAMS
    // @DisplayName: Parameter stream rate to ground station
    // @Description: Parameter stream rate to ground station
    // @Units: Hz
    // @Range: 0 10
    // @Increment: 1
    // @User: Advanced
    AP_GROUPINFO("PARAMS",   8, GCS_MAVLINK, streamRates[8],  10),
    AP_GROUPEND
};

void
GCS_MAVLINK_Tracker::data_stream_send(void)
{
    send_queued_parameters();

    if (tracker.in_mavlink_delay) {
        // don't send any other stream types while in the delay callback
        return;
    }

    if (!tracker.in_mavlink_delay) {
        tracker.DataFlash.handle_log_send(*this);
    }

    if (stream_trigger(STREAM_RAW_SENSORS)) {
        send_message(MSG_RAW_IMU1);
        send_message(MSG_RAW_IMU2);
        send_message(MSG_RAW_IMU3);
    }

    if (stream_trigger(STREAM_EXTENDED_STATUS)) {
        send_message(MSG_EXTENDED_STATUS1);
        send_message(MSG_EXTENDED_STATUS2);
        send_message(MSG_NAV_CONTROLLER_OUTPUT);
        send_message(MSG_GPS_RAW);
        send_message(MSG_GPS_RTK);
        send_message(MSG_GPS2_RAW);
        send_message(MSG_GPS2_RTK);
    }

    if (stream_trigger(STREAM_POSITION)) {
        send_message(MSG_LOCATION);
        send_message(MSG_LOCAL_POSITION);
    }

    if (stream_trigger(STREAM_RAW_CONTROLLER)) {
        send_message(MSG_SERVO_OUTPUT_RAW);
    }

    if (stream_trigger(STREAM_RC_CHANNELS)) {
        send_message(MSG_RADIO_IN);
        send_message(MSG_SERVO_OUTPUT_RAW);
    }

    if (stream_trigger(STREAM_EXTRA1)) {
        send_message(MSG_ATTITUDE);
    }

    if (stream_trigger(STREAM_EXTRA3)) {
        send_message(MSG_AHRS);
        send_message(MSG_HWSTATUS);
        send_message(MSG_SIMSTATE);
        send_message(MSG_MAG_CAL_REPORT);
        send_message(MSG_MAG_CAL_PROGRESS);
    }
}

/*
  We eavesdrop on MAVLINK_MSG_ID_GLOBAL_POSITION_INT and
  MAVLINK_MSG_ID_SCALED_PRESSUREs
*/
void Tracker::mavlink_snoop(const mavlink_message_t* msg)
{
    // return immediately if sysid doesn't match our target sysid
    if ((g.sysid_target != 0) && (g.sysid_target != msg->sysid)) {
        return;
    }

    switch (msg->msgid) {
    case MAVLINK_MSG_ID_HEARTBEAT:
    {
        mavlink_check_target(msg);
        break;
    }

    case MAVLINK_MSG_ID_GLOBAL_POSITION_INT:
    {
        // decode
        mavlink_global_position_int_t packet;
        mavlink_msg_global_position_int_decode(msg, &packet);
        tracking_update_position(packet);
        break;
    }
    
    case MAVLINK_MSG_ID_SCALED_PRESSURE:
    {
        // decode
        mavlink_scaled_pressure_t packet;
        mavlink_msg_scaled_pressure_decode(msg, &packet);
        tracking_update_pressure(packet);
        break;
    }
    }
}

// locks onto a particular target sysid and sets it's position data stream to at least 1hz
void Tracker::mavlink_check_target(const mavlink_message_t* msg)
{
    // exit immediately if the target has already been set
    if (target_set) {
        return;
    }

    // decode
    mavlink_heartbeat_t packet;
    mavlink_msg_heartbeat_decode(msg, &packet);

    // exit immediately if this is not a vehicle we would track
    if ((packet.type == MAV_TYPE_ANTENNA_TRACKER) ||
        (packet.type == MAV_TYPE_GCS) ||
        (packet.type == MAV_TYPE_ONBOARD_CONTROLLER) ||
        (packet.type == MAV_TYPE_GIMBAL)) {
        return;
    }

    // set our sysid to the target, this ensures we lock onto a single vehicle
    if (g.sysid_target == 0) {
        g.sysid_target = msg->sysid;
    }

    // send data stream request to target on all channels
    //  Note: this doesn't check success for all sends meaning it's not guaranteed the vehicle's positions will be sent at 1hz
    gcs().request_datastream_position(msg->sysid, msg->compid);
    gcs().request_datastream_airpressure(msg->sysid, msg->compid);

    // flag target has been set
    target_set = true;
}

uint8_t GCS_MAVLINK_Tracker::sysid_my_gcs() const
{
    return tracker.g.sysid_my_gcs;
}

void GCS_MAVLINK_Tracker::handleMessage(mavlink_message_t* msg)
{
    switch (msg->msgid) {

    // If we are currently operating as a proxy for a remote, 
    // alas we have to look inside each packet to see if it's for us or for the remote
    case MAVLINK_MSG_ID_REQUEST_DATA_STREAM:
    {
        handle_request_data_stream(msg, false);
        break;
    }


    case MAVLINK_MSG_ID_HEARTBEAT:
        break;

    case MAVLINK_MSG_ID_COMMAND_LONG:
    {
        // decode
        mavlink_command_long_t packet;
        mavlink_msg_command_long_decode(msg, &packet);
        
        MAV_RESULT result = MAV_RESULT_UNSUPPORTED;
        
        // do command
        send_text(MAV_SEVERITY_INFO,"Command received: ");
        
        switch(packet.command) {
            
            case MAV_CMD_PREFLIGHT_CALIBRATION:
            {
                if (is_equal(packet.param1,1.0f)) {
                    tracker.ins.init_gyro();
                    if (tracker.ins.gyro_calibrated_ok_all()) {
                        tracker.ahrs.reset_gyro_drift();
                        result = MAV_RESULT_ACCEPTED;
                    } else {
                        result = MAV_RESULT_FAILED;
                    }
                }
                if (is_equal(packet.param3,1.0f)) {
                    tracker.init_barometer(false);
                    // zero the altitude difference on next baro update
                    tracker.nav_status.need_altitude_calibration = true;
                    result = MAV_RESULT_ACCEPTED;
                }
                if (is_equal(packet.param4,1.0f)) {
                    // Can't trim radio
                    result = MAV_RESULT_UNSUPPORTED;
                } else if (is_equal(packet.param5,1.0f)) {
                    result = MAV_RESULT_ACCEPTED;
                    // start with gyro calibration
                    tracker.ins.init_gyro();
                    // reset ahrs gyro bias
                    if (tracker.ins.gyro_calibrated_ok_all()) {
                        tracker.ahrs.reset_gyro_drift();
                    } else {
                        result = MAV_RESULT_FAILED;
                    }
                    // start accel cal
                    tracker.ins.acal_init();
                    tracker.ins.get_acal()->start(this);
                } else if (is_equal(packet.param5,2.0f)) {
                    // start with gyro calibration
                    tracker.ins.init_gyro();
                    // accel trim
                    float trim_roll, trim_pitch;
                    if (tracker.ins.calibrate_trim(trim_roll, trim_pitch)) {
                        // reset ahrs's trim to suggested values from calibration routine
                        tracker.ahrs.set_trim(Vector3f(trim_roll, trim_pitch, 0));
                        result = MAV_RESULT_ACCEPTED;
                    } else {
                        result = MAV_RESULT_FAILED;
                    }
                }
                break;
            }

            case MAV_CMD_COMPONENT_ARM_DISARM:
                if (packet.target_component == MAV_COMP_ID_SYSTEM_CONTROL) {
                    if (is_equal(packet.param1,1.0f)) {
                        tracker.arm_servos();
                        result = MAV_RESULT_ACCEPTED;
                    } else if (is_zero(packet.param1))  {
                        tracker.disarm_servos();
                        result = MAV_RESULT_ACCEPTED;
                    } else {
                        result = MAV_RESULT_UNSUPPORTED;
                    }
                } else {
                    result = MAV_RESULT_UNSUPPORTED;
                }
            break;

            case MAV_CMD_GET_HOME_POSITION:
                send_home(tracker.ahrs.get_home());
                Location ekf_origin;
                if (tracker.ahrs.get_origin(ekf_origin)) {
                    send_ekf_origin(ekf_origin);
                }
                result = MAV_RESULT_ACCEPTED;
                break;

            case MAV_CMD_DO_SET_SERVO:
                if (tracker.servo_test_set_servo(packet.param1, packet.param2)) {
                    result = MAV_RESULT_ACCEPTED;
                }
                break;

                // mavproxy/mavutil sends this when auto command is entered 
            case MAV_CMD_MISSION_START:
                tracker.set_mode(AUTO, MODE_REASON_GCS_COMMAND);
                result = MAV_RESULT_ACCEPTED;
                break;

            case MAV_CMD_PREFLIGHT_REBOOT_SHUTDOWN:
            {
                if (is_equal(packet.param1,1.0f) || is_equal(packet.param1,3.0f)) {
                    // when packet.param1 == 3 we reboot to hold in bootloader
                    hal.scheduler->reboot(is_equal(packet.param1,3.0f));
                    result = MAV_RESULT_ACCEPTED;
                }
                break;
            }

            case MAV_CMD_ACCELCAL_VEHICLE_POS:
                result = MAV_RESULT_FAILED;

                if (tracker.ins.get_acal()->gcs_vehicle_position(packet.param1)) {
                    result = MAV_RESULT_ACCEPTED;
                }
                break;

            default:
                result = handle_command_long_message(packet);
                break;
        }
        mavlink_msg_command_ack_send(
            chan,
            packet.command,
            result);
        
        break;
    }
         
    // When mavproxy 'wp sethome' 
    case MAVLINK_MSG_ID_MISSION_WRITE_PARTIAL_LIST:
    {
        // decode
        mavlink_mission_write_partial_list_t packet;
        mavlink_msg_mission_write_partial_list_decode(msg, &packet);
        if (packet.start_index == 0)
        {
            // New home at wp index 0. Ask for it
            waypoint_receiving = true;
            waypoint_request_i = 0;
            waypoint_request_last = 0;
            send_message(MSG_NEXT_WAYPOINT);
        }
        break;
    }

    // XXX receive a WP from GCS and store in EEPROM if it is HOME
    case MAVLINK_MSG_ID_MISSION_ITEM:
    {
        // decode
        mavlink_mission_item_t packet;
        MAV_MISSION_RESULT result = MAV_MISSION_ACCEPTED;

        mavlink_msg_mission_item_decode(msg, &packet);

        struct Location tell_command = {};

        switch (packet.frame)
        {
        case MAV_FRAME_MISSION:
        case MAV_FRAME_GLOBAL:
        {
            tell_command.lat = 1.0e7f*packet.x;                                     // in as DD converted to * t7
            tell_command.lng = 1.0e7f*packet.y;                                     // in as DD converted to * t7
            tell_command.alt = packet.z*1.0e2f;                                     // in as m converted to cm
            tell_command.options = 0;                                     // absolute altitude
            break;
        }

#ifdef MAV_FRAME_LOCAL_NED
        case MAV_FRAME_LOCAL_NED:                         // local (relative to home position)
        {
            tell_command.lat = 1.0e7f*ToDeg(packet.x/
                                           (RADIUS_OF_EARTH*cosf(ToRad(home.lat/1.0e7f)))) + home.lat;
            tell_command.lng = 1.0e7f*ToDeg(packet.y/RADIUS_OF_EARTH) + home.lng;
            tell_command.alt = -packet.z*1.0e2f;
            tell_command.options = MASK_OPTIONS_RELATIVE_ALT;
            break;
        }
#endif

#ifdef MAV_FRAME_LOCAL
        case MAV_FRAME_LOCAL:                         // local (relative to home position)
        {
            tell_command.lat = 1.0e7f*ToDeg(packet.x/
                                           (RADIUS_OF_EARTH*cosf(ToRad(home.lat/1.0e7f)))) + home.lat;
            tell_command.lng = 1.0e7f*ToDeg(packet.y/RADIUS_OF_EARTH) + home.lng;
            tell_command.alt = packet.z*1.0e2f;
            tell_command.options = MASK_OPTIONS_RELATIVE_ALT;
            break;
        }
#endif

        case MAV_FRAME_GLOBAL_RELATIVE_ALT:                         // absolute lat/lng, relative altitude
        {
            tell_command.lat = 1.0e7f * packet.x;                                     // in as DD converted to * t7
            tell_command.lng = 1.0e7f * packet.y;                                     // in as DD converted to * t7
            tell_command.alt = packet.z * 1.0e2f;
            tell_command.options = MASK_OPTIONS_RELATIVE_ALT;                                     // store altitude relative!! Always!!
            break;
        }

        default:
            result = MAV_MISSION_UNSUPPORTED_FRAME;
            break;
        }

        if (result != MAV_MISSION_ACCEPTED) goto mission_failed;

        // Check if receiving waypoints (mission upload expected)
        if (!waypoint_receiving) {
            result = MAV_MISSION_ERROR;
            goto mission_failed;
        }

        // check if this is the HOME wp
        if (packet.seq == 0) {
            tracker.set_home(tell_command); // New home in EEPROM
            send_text(MAV_SEVERITY_INFO,"New HOME received");
            waypoint_receiving = false;
        }

mission_failed:
        // we are rejecting the mission/waypoint
        mavlink_msg_mission_ack_send(
            chan,
            msg->sysid,
            msg->compid,
            result,
            MAV_MISSION_TYPE_MISSION);
        break;
    }

    case MAVLINK_MSG_ID_MANUAL_CONTROL:
    {
        mavlink_manual_control_t packet;
        mavlink_msg_manual_control_decode(msg, &packet);
        tracker.tracking_manual_control(packet);
        break;
    }

    case MAVLINK_MSG_ID_GLOBAL_POSITION_INT: 
    {
        // decode
        mavlink_global_position_int_t packet;
        mavlink_msg_global_position_int_decode(msg, &packet);
        tracker.tracking_update_position(packet);
        break;
    }

    case MAVLINK_MSG_ID_SCALED_PRESSURE: 
    {
        // decode
        mavlink_scaled_pressure_t packet;
        mavlink_msg_scaled_pressure_decode(msg, &packet);
        tracker.tracking_update_pressure(packet);
        break;
    }

    default:
        handle_common_message(msg);
        break;
    } // end switch
} // end handle mavlink


/*
 *  a delay() callback that processes MAVLink packets. We set this as the
 *  callback in long running library initialisation routines to allow
 *  MAVLink to process packets while waiting for the initialisation to
 *  complete
 */
void Tracker::mavlink_delay_cb()
{
    static uint32_t last_1hz, last_50hz, last_5s;
    if (!gcs().chan(0).initialised) {
        return;
    }

    tracker.in_mavlink_delay = true;
    DataFlash.EnableWrites(false);

    uint32_t tnow = AP_HAL::millis();
    if (tnow - last_1hz > 1000) {
        last_1hz = tnow;
        gcs().send_message(MSG_HEARTBEAT);
        gcs().send_message(MSG_EXTENDED_STATUS1);
    }
    if (tnow - last_50hz > 20) {
        last_50hz = tnow;
        gcs_update();
        gcs_data_stream_send();
        notify.update();
    }
    if (tnow - last_5s > 5000) {
        last_5s = tnow;
        gcs().send_text(MAV_SEVERITY_INFO, "Initialising APM");
    }
    DataFlash.EnableWrites(true);
    tracker.in_mavlink_delay = false;
}

/*
 *  send data streams in the given rate range on both links
 */
void Tracker::gcs_data_stream_send(void)
{
    gcs().data_stream_send();
}

/*
 *  look for incoming commands on the GCS links
 */
void Tracker::gcs_update(void)
{
    gcs().update();
}

/**
   retry any deferred messages
 */
void Tracker::gcs_retry_deferred(void)
{
    gcs().retry_deferred();
}

Compass *GCS_MAVLINK_Tracker::get_compass() const
{
    return &tracker.compass;
}

/*
  set_mode() wrapper for MAVLink SET_MODE
 */
bool GCS_MAVLINK_Tracker::set_mode(uint8_t mode)
{
    switch (mode) {
    case AUTO:
    case MANUAL:
    case SCAN:
    case SERVO_TEST:
    case STOP:
        tracker.set_mode((enum ControlMode)mode, MODE_REASON_GCS_COMMAND);
        return true;
    }
    return false;
}

const AP_FWVersion &GCS_MAVLINK_Tracker::get_fwver() const
{
    return tracker.fwver;
}

void GCS_MAVLINK_Tracker::set_ekf_origin(const Location& loc)
{
    tracker.set_ekf_origin(loc);
}

/* dummy methods to avoid having to link against AP_Camera */
void AP_Camera::control_msg(mavlink_message_t const*) {}
void AP_Camera::configure(float, float, float, float, float, float, float) {}
void AP_Camera::control(float, float, float, float, float, float) {}
void AP_Camera::send_feedback(mavlink_channel_t chan) {}
/* end dummy methods to avoid having to link against AP_Camera */

// dummy method to avoid linking AFS
bool AP_AdvancedFailsafe::gcs_terminate(bool should_terminate, const char *reason) {return false;}