# Flight Controller Porting Guide
This topic is for developers who want to port PX4 to work with new flight controller hardware.
# PX4 Architecture
PX4 consists of two main layers: The board support and middleware layer on top of the host OS (NuttX, Linux or any other POSIX platform like Mac OS), and the applications (Flight Stack in src/modules (opens new window)). Please reference the PX4 Architectural Overview for more information.
This guide is focused only on the host OS and middleware as the applications/flight stack will run on any board target.
# Flight Controller Configuration File Layout
Board-specific initialisation file: /boards/px4/fmu-v5/init/rc.board (opens new window)
For example, for FMUv5:
- (All) Board-specific files: /boards/px4/fmu-v5 (opens new window).
- Build configuration: /boards/px4/fmu-v5/default.cmake (opens new window).
- Board specific header: /boards/px4/fmu-v5/nuttx-config/include/board.h (opens new window).
- A board-specific initialisation file is automatically included in startup scripts if found under the boards directory at init/rc.board.
- The file is used to start sensors (and other things) that only exist on a particular board. It may also be used to set a board's default parameters, UART mappings, and any other special cases.
- For FMUv5 you can see all the Pixhawk 4 sensors being started, and it also sets a larger LOGGER_BUF, and in AUTOCNF section (fresh setups) it sets the SYS_FMU_TASK parameter.
# Host Operating System Configuration
This section describes the purpose and location of the configuration files required for each supported host operating system to port them to new flight controller hardware.
Linux boards do not include the OS and kernel configuration. These are already provided by the Linux image available for the board (which needs to support the inertial sensors out of the box).
- The boot file system (startup script) is located in: ROMFS/px4fmu_common (opens new window)
# Middleware Components and Configuration
This section describes the various middleware components, and the configuration file updates needed to port them to new flight controller hardware.
# QuRT / Hexagon
- Driver files are located in: src/drivers (opens new window).
- The OS configuration is part of the default Linux image (TODO: Provide location of LINUX IMAGE and flash instructions).
- The PX4 middleware configuration is located in src/drivers/boards (opens new window). TODO: ADD BUS CONFIG
# RC UART Wiring Recommendations
It is generally recommended to connect RC via separate RX and TX pins to the microcontroller. If however RX and TX are connected together, the UART has to be put into singlewire mode to prevent any contention. This is done via board config and manifest files. One example is px4fmu-v5 (opens new window). ## Officially Supported Hardware
The PX4 project supports and maintains the FMU standard reference hardware and any boards that are compatible with the standard. This includes the Pixhawk-series (opens new window) (see the user guide for a full list of officially supported hardware (opens new window)).
Every officially supported board benefits from:
- PX4 Port available in the PX4 repository
- Automatic firmware builds that are accessible from QGroundControl
- Compatibility with the rest of the ecosystem
- Automated checks via CI - safety remains paramount to this community
- Flight testing
We encourage board manufacturers to aim for full compatibility with the FMU spec (opens new window). With full compatibility you benefit from the ongoing day-to-day development of PX4, but have none of the maintenance costs that come from supporting deviations from the specification.
Manufacturers should carefully consider the cost of maintenance before deviating from the specification (the cost to the manufacturer is proportional to the level of divergence).
We welcome any individual or company to submit their port for inclusion in our supported hardware, provided they are willing to follow our Code of Conduct (opens new window) and work with the Dev Team to provide a safe and fulfilling PX4 experience to their customers.
It's also important to note that the PX4 dev team has a responsibility to release safe software, and as such we require any board manufacturer to commit any resources necessary to keep their port up-to-date, and in a working state.
If you want to have your board officially supported in PX4:
- The start script is located in posix-configs/ (opens new window).
- Hardware must be made available to the PX4 Dev Team so that they can validate the port (contact firstname.lastname@example.org for guidance on where to ship hardware for testing).
- The board must pass full test suite and flight testing.
The PX4 project reserves the right to refuse acceptance of new ports (or remove current ports) for failure to meet the requirements set by the project.
You can reach out to the core developer team and community on the official support channels.