examples: remove auto-takeoff, make VIO feed a background tool

The vision odometry example now does NOT arm, takeoff, or control the
drone. It only feeds VIO data. The user flies the drone however they
like (QGroundControl, RC, mission, another script) while this runs
alongside. Press Ctrl+C to stop.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: alireza787b

examples/vision_odometry.py

@@ -3,18 +3,24 @@
 """
 Vision Odometry Ground Truth Feedback -- MAVSDK Example
 
-Demonstrates VIO (Visual-Inertial Odometry) integration with PX4 using
-the MAVSDK Mocap plugin. In simulation, it reads the drone's actual
-position as "ground truth" and feeds it back to PX4 as external vision
-data, with configurable noise and delay to simulate a real VIO sensor.
+Feeds simulated VIO (Visual-Inertial Odometry) data to PX4 using the
+MAVSDK Mocap plugin. Reads the simulator's ground truth position, adds
+configurable noise and delay, and sends it back as external vision
+odometry. This is for testing and education -- the simulator looks
+and behaves completely normally while this script runs alongside it.
+
+This script does NOT arm, takeoff, or control the drone in any way.
+You fly the drone however you like (QGroundControl, RC, mission, or
+another MAVSDK script) while this script feeds VIO data in the
+background. Press Ctrl+C to stop.
 
 How it works:
     1. Connects to PX4 and configures EKF2 for vision fusion
-    2. Arms and takes off (using GPS in simulation)
-    3. Reads position from the simulator as ground truth
-    4. Adds configurable Gaussian noise and delay
-    5. Sends the result to PX4 as ODOMETRY at 30 Hz via Mocap plugin
-    6. Displays real-time EKF2 position so you can see fusion working
+    2. Reads position from the simulator as ground truth
+    3. Adds configurable Gaussian noise and delay
+    4. Sends the result to PX4 as ODOMETRY at 30 Hz via Mocap plugin
+    5. Displays real-time EKF2 position and fusion health status
+    6. Runs until you press Ctrl+C
 
 Adjust the parameters below to experiment:
     - Increase NOISE_POS_STDDEV_M to see EKF2 handle noisy data
@@ -35,7 +41,11 @@
     Install a MAVSDK build that includes these changes.
 
 Usage:
-    python3 vision_odometry.py
+    1. Start PX4 simulator
+    2. Run: python3 vision_odometry.py
+    3. Fly the drone normally (QGroundControl, RC, mission, etc.)
+    4. Watch the VIO feed and EKF2 fusion status in the terminal
+    5. Press Ctrl+C to stop
 """
 
 import asyncio
@@ -66,9 +76,7 @@
 DELAY_MS = 0  # Sensor delay (ms). Real: 10-50. 0 = off.
 QUALITY_PERCENT = 75  # Confidence 0-100. See EKF2_EV_QMIN.
 
-# -- Flight --
-FLIGHT_ALT_M = 5.0  # Takeoff altitude (m)
-HOVER_TIME_S = 30  # How long to feed VIO while hovering (s)
+# -- Display --
 DISPLAY_INTERVAL_S = 2.0  # Status print interval (s)
 
 # -- EKF2 Vision Fusion --
@@ -96,7 +104,6 @@ def validate_odometry_api():
     fields added by MAVSDK-Proto PR #395. If your MAVSDK version
     does not include these, you will see a clear error here.
     """
-    # Check constructor accepts the three new fields
     try:
         sig = inspect.signature(Odometry.__init__)
         # Original API: self + 8 fields = 9 params
@@ -115,7 +122,6 @@ def validate_odometry_api():
     except (ValueError, TypeError) as exc:
         raise SystemExit(f"[ERROR] Cannot inspect Odometry API: {exc}") from exc
 
-    # Check MavEstimatorType enum exists
     if not hasattr(Odometry, "MavEstimatorType"):
         raise SystemExit(
             "[ERROR] Odometry.MavEstimatorType not found.\n"
@@ -141,49 +147,20 @@ async def run():
             break
 
     await configure_ekf2(drone)
-
-    print("\nWaiting for position estimate...")
-    async for health in drone.telemetry.health():
-        if health.is_global_position_ok and health.is_home_position_ok:
-            print("[OK] Position estimate ready")
-            break
-
-    print("\n-- Arming")
-    await drone.action.arm()
-
-    print(f"-- Taking off to {FLIGHT_ALT_M:.0f} m")
-    await drone.action.set_takeoff_altitude(FLIGHT_ALT_M)
-    await drone.action.takeoff()
-
-    print("-- Waiting for takeoff...")
-    await asyncio.sleep(10)
-    print("[OK] Hovering -- starting VIO feed\n")
-
     print_settings_summary()
 
-    # Run VIO feed, status monitor, and health watch concurrently
-    stop_event = asyncio.Event()
-    vio_task = asyncio.ensure_future(vio_feed_loop(drone, stop_event))
-    monitor_task = asyncio.ensure_future(monitor_status(drone, stop_event))
-    health_task = asyncio.ensure_future(watch_fusion_health(drone, stop_event))
-
-    await asyncio.sleep(HOVER_TIME_S)
-    stop_event.set()
-
-    await asyncio.gather(
-        vio_task,
-        monitor_task,
-        health_task,
-        return_exceptions=True,
-    )
+    print("VIO feed is running. Fly the drone normally")
+    print("(QGroundControl, RC, mission, etc.). Press Ctrl+C to stop.\n")
 
-    print("\n-- Landing")
-    await drone.action.land()
+    # Run VIO feed, status monitor, and health watch concurrently
+    vio_task = asyncio.ensure_future(vio_feed_loop(drone))
+    monitor_task = asyncio.ensure_future(monitor_status(drone))
+    health_task = asyncio.ensure_future(watch_fusion_health(drone))
 
-    async for in_air in drone.telemetry.in_air():
-        if not in_air:
-            print("[OK] Landed")
-            break
+    try:
+        await asyncio.gather(vio_task, monitor_task, health_task)
+    except asyncio.CancelledError:
+        pass
 
     print_footer()
 
@@ -199,6 +176,7 @@ async def configure_ekf2(drone):
     for name, value, desc in params:
         await drone.param.set_param_int(name, value)
         print(f"  {name:20s} = {value:2d}  ({desc})")
+    print()
 
 
 def print_settings_summary():
@@ -220,7 +198,7 @@ def print_settings_summary():
 # ===================================================================
 
 
-async def vio_feed_loop(drone, stop_event):
+async def vio_feed_loop(drone):
     """Read ground truth, add noise/delay, send as vision odometry.
 
     In simulation, position_velocity_ned() returns the EKF2 estimate,
@@ -245,9 +223,6 @@ async def vio_feed_loop(drone, stop_event):
         delay_buf = None
 
     async for pos_vel in drone.telemetry.position_velocity_ned():
-        if stop_event.is_set():
-            break
-
         n = pos_vel.position.north_m
         e = pos_vel.position.east_m
         d = pos_vel.position.down_m
@@ -302,7 +277,7 @@ async def vio_feed_loop(drone, stop_event):
 # ===================================================================
 
 
-async def monitor_status(drone, stop_event):
+async def monitor_status(drone):
     """Print EKF2 position at regular intervals."""
     print(
         f"{'Time':>6s}  {'North':>8s}  {'East':>8s}  {'Down':>8s}  {'Vn':>6s} {'Ve':>6s} {'Vd':>6s}"
@@ -313,9 +288,6 @@ async def monitor_status(drone, stop_event):
     last_print = 0.0
 
     async for pv in drone.telemetry.position_velocity_ned():
-        if stop_event.is_set():
-            break
-
         elapsed = time.monotonic() - start
         if elapsed - last_print < DISPLAY_INTERVAL_S:
             await asyncio.sleep(0.2)
@@ -334,13 +306,11 @@ async def monitor_status(drone, stop_event):
         )
 
 
-async def watch_fusion_health(drone, stop_event):
+async def watch_fusion_health(drone):
     """Report EKF2 fusion health changes."""
     was_ok = False
 
     async for health in drone.telemetry.health():
-        if stop_event.is_set():
-            break
         is_ok = health.is_local_position_ok
         if is_ok and not was_ok:
             print("[HEALTH] Local position OK -- vision fusion active")
@@ -353,7 +323,8 @@ def print_footer():
     """Print final guidance for the user."""
     print()
     print("=" * 60)
-    print("Done! Adjust parameters at the top of this file:")
+    print("VIO feed stopped. Adjust parameters at the top of")
+    print("this file to experiment:")
     print("  NOISE_POS_STDDEV_M   -- increase to stress EKF2")
     print("  DELAY_MS             -- simulate sensor latency")
     print("  QUALITY_PERCENT      -- lower with EKF2_EV_QMIN > 0")
@@ -362,4 +333,7 @@ def print_footer():
 
 
 if __name__ == "__main__":
-    asyncio.run(run())
+    try:
+        asyncio.run(run())
+    except KeyboardInterrupt:
+        print("\n[OK] Stopped by user")