Pavel Guzenfeld
2a69f92bb1
* fix(uxrce_dds_client): fix session reconnection after agent restart When the Micro XRCE-DDS Agent is restarted (e.g. via systemd or Docker), the PX4 client stays "Running, disconnected" forever and never re-establishes the session. Three bugs prevented reconnection: 1. session.on_pong_flag was never reset after being checked. Once set to 1 by the first successful pong, it stayed 1 forever, causing checkConnectivity() to believe pings were still succeeding even after the agent was gone. Fixed by resetting to 0 after reading. 2. _subs->reset() was never called during session teardown. Stale uORB file descriptors from the previous session persisted across reconnection attempts, causing the new session's publishers to malfunction. Fixed by calling _subs->reset() in deleteSession(). 3. _connected was not explicitly reset in deleteSession(). While the outer loop checked this flag, explicitly clearing it ensures clean state for the next reconnection attempt. Closes #26022 Signed-off-by: Pavel Guzenfeld <pavelgu@gmail.com> * fix(uxrce_dds_client): clear fds[].events in reset() for reconnection Without clearing events, init() skips orb_subscribe() on reconnect because the POLLIN guard (fds[idx].events == 0) is never true again. This causes all fds to remain at -1, px4_poll() returns 0, TX rate stays zero, and the client enters a disconnect/reconnect loop. Reported-by: sansha (tested on Pixhawk 6X with serial transport) * ci: re-trigger SITL tests (flaky offboard test) * docs(uxrce_dds_client): explain why reset() clears fds[].events --------- Signed-off-by: Pavel Guzenfeld <pavelgu@gmail.com>
The autopilot stack the industry builds on.
About
PX4 is an open-source autopilot stack for drones and unmanned vehicles. It supports multirotors, fixed-wing, VTOL, rovers, and many more experimental platforms from racing quads to industrial survey aircraft. It runs on NuttX, Linux, and macOS. Licensed under BSD 3-Clause.
Why PX4
Modular architecture. PX4 is built around uORB, a DDS-compatible publish/subscribe middleware. Modules are fully parallelized and thread safe. You can build custom configurations and trim what you don't need.
Wide hardware support. PX4 runs on a wide range of autopilot boards and supports an extensive set of sensors, telemetry radios, and actuators through the Pixhawk ecosystem.
Developer friendly. First-class support for MAVLink and DDS / ROS 2 integration. Comprehensive SITL simulation, hardware-in-the-loop testing, and log analysis tools. An active developer community on Discord and the weekly dev call.
Vendor neutral governance. PX4 is hosted under the Dronecode Foundation, part of the Linux Foundation. Business-friendly BSD-3 license. No single vendor controls the roadmap.
Supported Vehicles
 Multicopter |
 Fixed Wing |
 VTOL |
 Rover |
…and many more: helicopters, autogyros, airships, submarines, boats, and other experimental platforms. These frames have basic support but are not part of the regular flight-test program. See the full airframe reference.
Try PX4
Run PX4 in simulation with a single command. No build tools, no dependencies beyond Docker:
docker run --rm -it -p 14550:14550/udp px4io/px4-sitl:latest
Open QGroundControl and fly. See PX4 Simulation Quickstart for more options.
Build from Source
git clone https://github.com/PX4/PX4-Autopilot.git --recursive
cd PX4-Autopilot
make px4_sitl
Note
See the Development Guide for toolchain setup and build options.
Documentation & Resources
| Resource | Description |
|---|---|
| User Guide | Build, configure, and fly with PX4 |
| Developer Guide | Modify the flight stack, add peripherals, port to new hardware |
| Airframe Reference | Full list of supported frames |
| Autopilot Hardware | Compatible flight controllers |
| Release Notes | What's new in each release |
| Contribution Guide | How to contribute to PX4 |
Community
- Weekly Dev Call — open to all developers (Dronecode calendar)
- Discord — Join the Dronecode server
- Discussion Forum — PX4 Discuss
- Maintainers — see
MAINTAINERS.md - Contributor Stats — LFX Insights
Contributing
We welcome contributions of all kinds — bug reports, documentation, new features, and code reviews. Please read the Contribution Guide to get started.
Citation
If you use PX4 in academic work, please cite it. BibTeX:
@software{px4_autopilot,
author = {Meier, Lorenz and {The PX4 Contributors}},
title = {{PX4 Autopilot}},
publisher = {Zenodo},
doi = {10.5281/zenodo.595432},
url = {https://px4.io}
}
The DOI above is a Zenodo concept DOI that always resolves to the latest release. For a version-pinned citation, see the Zenodo record or our CITATION.cff.
Governance
The PX4 Autopilot project is hosted by the Dronecode Foundation, a Linux Foundation Collaborative Project. Dronecode holds all PX4 trademarks and serves as the project's legal guardian, ensuring vendor-neutral stewardship — no single company owns the name or controls the roadmap. The source code is licensed under the BSD 3-Clause license, so you are free to use, modify, and distribute it in your own projects.
