VIO

This guide describes indoor flight without GPS using a VIO/SLAM odometry source (from RSFastLivo) and two integration paths to PX4:

  • Path A — MAVROS (serial TELEM2): simplest and fully offline.

  • Path B — uXRCE-DDS agent/bridge: native PX4–ROS 2 DDS pipeline.

The pipeline at a glance

  1. Create the ROS 2 workspace on the Jetson.

  2. Start the AC1 ROS2 Driver (LiDAR).

  3. Start RSFastLivo (produces odometry).

  4. Feed odometry to PX4 via MAVROS or uXRCE-DDS.

  5. Fly indoors in Position/Offboard without GPS.

Prerequisites

  • Pixhawk flashed with PX4.

  • Jetson flashed and ROS 2 installed.

  • TELEM2 UART wired between Pixhawk ↔ Jetson (no network required).

  • AC1 powered via UBEC and USB to Jetson.

Workspace & drivers

# Create a ROS 2 workspace on Jetson
mkdir -p ~/ros2_ws/src && cd ~/ros2_ws

# AC1 driver (publishes point clouds)
cd ~/ros2_ws/src
git clone https://github.com/RoboSense-Robotics/robosense_ac_ros2_sdk_infra.git

# RSFastLivo (produces odometry)
git clone https://github.com/RoboSense-Robotics/robosense_ac_slam.git

# Build
cd ~/ros2_ws
colcon build --symlink-install
source install/setup.bash

Run sensors & SLAM

# 1) Start AC1 driver
ros2 launch robosense_ac_ros2_sdk_infra rviz.launch.py

# 2) Start RSFastLivo (publishes odometry)
ros2 launch robosense_ac_slam demo.launch.py

Choose your integration path

Path A — MAVROS over TELEM2 (recommended, fully offline)

# Install MAVROS on Jetson
sudo apt update
sudo apt install -y ros-humble-mavros ros-humble-mavros-extras
sudo /opt/ros/humble/lib/mavros/install_geographiclib_datasets.sh

# Start MAVROS with serial FCU URL (adjust port/baud to your wiring)
ros2 launch mavros px4.launch fcu_url:=/dev/ttyTHS1:921600

# Feed RSFastLivo odometry to MAVROS vision topics:
# Publish nav_msgs/Odometry to:
/mavros/odometry/out

Path B — uXRCE-DDS (PX4 ↔ ROS 2 DDS bridge)

# Start the Micro XRCE-DDS Agent on Jetson
# (Adjust serial device & baud to match TELEM2)
MicroXRCEAgent serial --dev /dev/ttyTHS1 -b 921600

# On Pixhawk (via QGC MAVLink console), start the client
uxrce_dds_client start -t serial -d /dev/ttyS2 -b 921600

# Publish RSFastLivo odometry as a px4_msgs/VehicleVisualOdometry topic into:
/fmu/in/vehicle_visual_odometry
# (use your ROS 2 node or example publisher)
# PX4 will fuse this as external vision.

PX4/QGC parameter checklist (indoor EV)

# Set these in QGroundControl → Parameters (names may vary slightly by PX4 version):

# Arming without GPS
COM_ARM_WO_GPS = 1

# External vision aiding
EKF2_AID_MASK → enable Vision position, Vision yaw (optionally Vision velocity)
EKF2_HGT_MODE = Vision

# MAVLink on TELEM2 (if using MAVROS)
MAV_1_CONFIG = TELEM2
MAV_1_MODE   = Normal
MAV_1_BAUD   = 921600  (or your chosen baud)

# Indoor flight
# Disable GPS fusion (leave GPS disconnected or ensure EKF does not require GPS)
# Set appropriate failsafe behavior for GPS-denied operation

Safety & frame conventions

# - Bench-test first with props off; confirm EKF is using vision in QGC.
# - Ensure correct frame alignment:
#   RSFastLivo output (usually ENU) vs PX4 (NED).
#   MAVROS handles ENU↔NED, but verify orientation and yaw sign.
# - Secure all cables; avoid LiDAR motion to reduce distortion.

Arming & indoor flight

# With MAVROS: arm/disarm and mode change via QGC or MAVROS

# Example (ensure safety is observed!)
ros2 service call /mavros/cmd/arming mavros_msgs/srv/CommandBool "{value: true}"
ros2 topic pub /mavros/set_mode mavros_msgs/msg/State "mode: 'OFFBOARD'"

# With uXRCE-DDS: use QGC or your ROS 2 flight app to send mode/arming commands
# Start in a wide, texture-rich indoor area; verify steady pose before takeoff

Troubleshooting quick tips

# No odometry in PX4:
# - Check RSFastLivo is publishing, and topic remaps to MAVROS/uXRCE inputs.
# - Verify TELEM2 baud and serial device.

# EKF rejecting vision:
# - Recheck EKF2_AID_MASK and EKF2_HGT_MODE.
# - Confirm timestamp continuity and reasonable covariance on vision data.