Plane: added MANUAL_CONTROL support

allows for joystick with QGC

ArduPlane/GCS_Mavlink.cpp

@@ -1475,6 +1475,34 @@ void GCS_MAVLINK_Plane::handleMessage(mavlink_message_t* msg)
         break;
     }
 
+    case MAVLINK_MSG_ID_MANUAL_CONTROL:
+    {
+        if (msg->sysid != plane.g.sysid_my_gcs) break;                         // Only accept control from our gcs
+
+        mavlink_manual_control_t packet;
+        mavlink_msg_manual_control_decode(msg, &packet);
+
+        bool override_active = false;
+        int16_t roll = (packet.y == INT16_MAX) ? 0 : plane.channel_roll->get_radio_min() + (plane.channel_roll->get_radio_max() - plane.channel_roll->get_radio_min()) * (packet.y + 1000) / 2000.0f;
+        int16_t pitch = (packet.x == INT16_MAX) ? 0 : plane.channel_pitch->get_radio_min() + (plane.channel_pitch->get_radio_max() - plane.channel_pitch->get_radio_min()) * (-packet.x + 1000) / 2000.0f;
+        int16_t throttle = (packet.z == INT16_MAX) ? 0 : plane.channel_throttle->get_radio_min() + (plane.channel_throttle->get_radio_max() - plane.channel_throttle->get_radio_min()) * (packet.z) / 1000.0f;
+        int16_t yaw = (packet.r == INT16_MAX) ? 0 : plane.channel_rudder->get_radio_min() + (plane.channel_rudder->get_radio_max() - plane.channel_rudder->get_radio_min()) * (packet.r + 1000) / 2000.0f;
+
+        override_active |= hal.rcin->set_override(uint8_t(plane.rcmap.roll() - 1), roll);
+        override_active |= hal.rcin->set_override(uint8_t(plane.rcmap.pitch() - 1), pitch);
+        override_active |= hal.rcin->set_override(uint8_t(plane.rcmap.throttle() - 1), throttle);
+        override_active |= hal.rcin->set_override(uint8_t(plane.rcmap.yaw() - 1), yaw);
+
+        if (override_active) {
+            plane.failsafe.last_valid_rc_ms = AP_HAL::millis();
+            plane.failsafe.AFS_last_valid_rc_ms =  plane.failsafe.last_valid_rc_ms;
+        }
+        
+        // a manual control message is considered to be a 'heartbeat' from the ground station for failsafe purposes
+        plane.failsafe.last_heartbeat_ms = AP_HAL::millis();
+        break;
+    }
+    
     case MAVLINK_MSG_ID_HEARTBEAT:
     {
         // We keep track of the last time we received a heartbeat from