multicopter: minimize dt jitter by using estimate timestamp_sample

src/modules/flight_mode_manager/FlightModeManager.cpp

@@ -99,7 +99,7 @@ void FlightModeManager::Run()
 	vehicle_local_position_s vehicle_local_position;
 
 	if (_vehicle_local_position_sub.update(&vehicle_local_position)) {
-		const hrt_abstime time_stamp_now = hrt_absolute_time();
+		const hrt_abstime time_stamp_now = vehicle_local_position.timestamp_sample;
 		// Guard against too small (< 0.2ms) and too large (> 100ms) dt's.
 		const float dt = math::constrain(((time_stamp_now - _time_stamp_last_loop) / 1e6f), 0.0002f, 0.1f);
 		_time_stamp_last_loop = time_stamp_now;

src/modules/mc_att_control/mc_att_control_main.cpp

@@ -263,8 +263,8 @@ MulticopterAttitudeControl::Run()
 		}
 
 		// Guard against too small (< 0.2ms) and too large (> 20ms) dt's.
-		const float dt = math::constrain(((v_att.timestamp - _last_run) * 1e-6f), 0.0002f, 0.02f);
-		_last_run = v_att.timestamp;
+		const float dt = math::constrain(((v_att.timestamp_sample - _last_run) * 1e-6f), 0.0002f, 0.02f);
+		_last_run = v_att.timestamp_sample;
 
 		/* check for updates in other topics */
 		_manual_control_setpoint_sub.update(&_manual_control_setpoint);

src/modules/mc_pos_control/MulticopterPositionControl.cpp

@@ -291,7 +291,7 @@ void MulticopterPositionControl::Run()
 	vehicle_local_position_s local_pos;
 
 	if (_local_pos_sub.update(&local_pos)) {
-		const hrt_abstime time_stamp_now = local_pos.timestamp;
+		const hrt_abstime time_stamp_now = local_pos.timestamp_sample;
 		const float dt = math::constrain(((time_stamp_now - _time_stamp_last_loop) * 1e-6f), 0.002f, 0.04f);
 		_time_stamp_last_loop = time_stamp_now;