Flight-control firmware

Two kinds of cockpit

Open flight software splits the way wartime aviation split between a fighter and a bomber. One family is built for a pilot on sticks: fast loops, rates, a picture in the goggles. The other is built for a navigator: waypoints, return-to-home, airspeed hold, a mission that continues if the radio goes quiet.

You can put navigation on a racer, and you can fly a mapping plane by hand. The firmware still has a centre of gravity. Pick the project whose centre matches the job, then flash a board that the project actually supports.

Firmware is not a paint job. Changing from Betaflight to INAV, or from ArduPilot to PX4, is a change of standing orders. The radio may stay. The modes, the configurator, and the failsafe will not.

How to read this list

Each project below is still public source, with a community and a flashing tool. Historical names (MultiWii, Baseflight, Cleanflight, OpenPilot) are here so the family tree makes sense. They are not where a new build should start.

Licences matter if you ship a product. GPLv3 (Betaflight, INAV, ArduPilot) expects you to share changes. BSD / permissive (PX4) is easier to close. Read the file in the repo, not a forum summary.

Quick plate

Which stack for which machine

If you are building	Start here	Why
5-inch FPV racer or freestyle	Betaflight	The default mixer, filter, and rates language of that sport.
GPS quad, long-range, or a flying wing that must come home	INAV	Navigation without leaving the FPV-board world.
Survey plane, copter, rover, or boat on one ecosystem	ArduPilot	The broadest vehicle list and the oldest continuous mission stack.
Research, ROS, or a company airframe	PX4	Modular, permissive licence, strong companion-computer story.
Collective-pitch helicopter	Rotorflight	Swashplate and governor work that Betaflight does not pretend to do.
University lab, tiny indoor quad	Crazyflie	A whole research platform, not just a mixer.
Raspberry Pi on the aircraft	Companion, or ArduPilot/PX4 Linux	A Pi is a computer. Pair it with a real FC, or use a supported hat. Not a Betaflight target.

Stick-flying family

From MultiWii to the modern racer

betaflight.com / GPLv3

Betaflight

The standard firmware on FPV miniquads. It exists to make a gyro, four motors, and a set of rates feel like one aircraft. The loop is fast, the filter stack is deep, and the configurator is how most pilots first see a PID. It does not try to be a survey autopilot. Position hold is not the point; the point is that the craft stays where you put the sticks.

Our simulator dossier notes that WebFPVSimulator compiles a Betaflight 4.5.1 loop to WebAssembly for that reason: this is the feel people mean when they say “a real quad.”

Source on GitHub

inavflight.com / GPLv3

INAV

A fork of the same Cleanflight tree, aimed at aircraft that must know where they are. GPS return-to-home, waypoint missions, cruise and altitude hold, flying wings and multirotors on one configurator. If Betaflight is a fighter, INAV is the army co-operation machine: still a small board, but with a map and a lost-link plan.

Pilots often move here when a long-range quad or a foam wing outgrows “just fly it home by eye.” The radio and the FPV camera stay familiar. The modes do not.

Source on GitHub

emuflight.github.io / GPLv3

EmuFlight

A Betaflight-line fork that treats the tune as the whole problem: different filter and PID opinions, a following among pilots who want a particular feel the mainline tree will not ship. Same class of aircraft, same kind of configurator, a different set of standing orders in the loop.

Worth knowing so a dump file or a “flash this hex” thread does not surprise you. Not a second navigation stack.

Source on GitHub

rotorflight.org / GPLv3

Rotorflight

Collective-pitch helicopters need a swashplate, a governor, and a tail that is not just a yaw motor. Rotorflight takes the Betaflight engineering culture and spends it on that machine. If you came from a quad, this is the first firmware that will talk to you about cyclic and collective instead of four equal arms.

Source on GitHub

Lineage, so the old names make sense

MultiWii (around 2010) put a cheap Wii gyro on an Arduino and taught a generation that a mixer could live in a hobby board. Baseflight moved that idea onto 32-bit STM32. Cleanflight organised the community and the configurator. Betaflight and INAV grew out of that hangar. You will still see the names on dusty blogs. Flash the living trees, not the museum pieces.

Mission family

Autopilots that plan a route

ardupilot.org / GPLv3

ArduPilot

The oldest major stack that is still the default answer for “I want an unmanned vehicle, not a toy.” ArduCopter, ArduPlane, ArduRover, and ArduSub share one project. Mission Planner on Windows is the classic ground station; QGroundControl and others also speak its MAVLink dialect. It will fly a mapping wing, a heavy copter, a boat, or a rover with the same ideas: modes, geofence, a mission file, a log you can read after.

Context: this is the firmware that grew up with DIY Drones in the late 2000s and never stayed a quad-only toy. If your job is hours on station or a waypoint list, start the briefing here. Missions, docks, and the AI layer sit on the autonomy plate.

Source on GitHub

px4.io / BSD-3 / permissive

PX4 Autopilot

The other professional-grade open stack, under the Dronecode foundation. Modular by design: a flight stack that expects a companion computer, ROS 2, and cameras that think. QGroundControl is the usual briefing table. Manufacturers like the licence because they can ship a product without publishing every change – which is also why researchers and companies sit in the same hangar.

If ArduPilot feels like a well-worn squadron manual, PX4 feels like a modern instrument bay: more pieces, more ways to wire a computer next to the FC, a different culture of modules and messages.

Source on GitHub

paparazziuav.org / GPLv2

Paparazzi UAV

Started in 2003 at ENAC in France, before most of the names above existed. A complete system: airborne code, a ground station, and a taste for unusual airframes – flying wings, clouds of swarms, academic experiments. It is not the first download for a backyard 5-inch. It is the reminder that open autopilots are older than the smartphone gyro.

Source on GitHub

Ground stations / MAVLink

The other half of the cockpit

Firmware is mute without a place to write missions and read logs. Betaflight Configurator and INAV Configurator are the stick-flying benches. Mission Planner is the ArduPilot chart table. QGroundControl talks to PX4 and ArduPilot over MAVLink, the common telegram format for modes, waypoints, and telemetry. Learn the ground station with the firmware. They are one crew.

Other hangars

Research, history, and near neighbours

bitcraze.io / BSD

Crazyflie

A nano-quad research platform from Bitcraze. Open firmware, a Python API, positioning decks, and a culture of labs rather than race tracks. If the aircraft must fit in a hand and publish a paper, this is the line.

Firmware source

Historical

OpenPilot, LibrePilot, dRonin

OpenPilot was an early 32-bit autopilot with a polished GCS. LibrePilot and dRonin carried pieces of that tree after the project fractured. Useful when you inherit an old board. Not where a new student should enlist.

Not firmware, still open

Radios you will pair with it

ExpressLRS is the open command link most FPV pilots flash next. Crossfire is closed. Digital video is mostly vendor stacks. The FC project and the radio project are separate briefings that have to agree on a serial protocol (CRSF, SBUS, MAVLink).

Companion and Linux boards

Can you use a Raspberry Pi?

Yes – with the mission stacks. A Raspberry Pi is a small Linux computer, not an STM32 flight controller. It will not replace a Betaflight board on a 5-inch racer. It will sit next to a Pixhawk, or, on some ArduPilot and PX4 builds, it will be the autopilot if you add the right sensor hat.

Think of two jobs. The usual one: the Pi is the navigator’s table. A real FC still runs the mixer at a kilohertz. The Pi talks MAVLink or XRCE-DDS, runs a camera, ROS 2, a detector, or a ground-station proxy. That pairing works with ArduPilot, PX4, and INAV, and it is how most autonomy projects use a Pi 4 or Pi 5.

The rarer job: the Pi itself flies the aircraft. ArduPilot’s Linux port (PilotPi, Navio2, and similar hats) puts gyros and a PWM rail on a HAT so the Pi is the FC. PX4 has also shipped on Navio2-class Linux boards. You gain USB, cameras, and a full OS. You give up the hard real-time certainty of a bare STM32. Fine for a slow scout. Wrong for a gate racer.

Quick plate

Betaflight, EmuFlight, Rotorflight – no. Flash an F4, F7, or H7 board. The Pi can only watch (OSD, logs, a camera), not fly the loop.
INAV – same as above for the mixer. A Pi can be a companion for video or a GCS, not the INAV target.
ArduPilot – yes as companion, and yes as the autopilot with a supported Linux hat (Navio2, PilotPi, and the current Linux board list).
PX4 – yes as companion (the common path). Linux/Navio-style targets exist; most people still put PX4 on a Pixhawk and ROS on the Pi.
Paparazzi, Crazyflie labs – Pi is usually the ground or swarm computer, not the airborne STM32.

Companion – the useful default

Pi + a real FC

Serial or USB from Pixhawk, Cube, Matek, or another MAVLink board into a Pi 4 or Pi 5. Run MAVSDK, MAVROS, or PX4’s uXRCE-DDS. Add a camera for mapping or YOLO. This is the stack the autonomy plate assumes. Power the Pi from a BEC that will not brown out when the motors bite.

Autopilot on Linux

ArduPilot and PX4 on the Pi

Buy a hat that already has a gyro, compass, and PWM or DShot outputs – do not invent your own IMU wiring. Follow the project’s Linux board page, not a random image. SITL on a Pi is also valid: the firmware flies a simulated aircraft while you learn missions with no props.

ArduPilot on Navio2 / Linux

What the Pi is bad at

Racing loops and hard timing

Linux will pause. A gyro loop must not. That is why Betaflight stays on a microcontroller. A Pi 5 can run a small detector; it will not feel like a Jetson Orin, and it will not out-time an H7. Use it for maps, cameras, and missions. Leave acro on carbon and STM32.

Discipline at the flashing bench

Dump the current firmware before you overwrite a working aircraft. Confirm the board target – the same STM32 chip is not the same hex. Bind the radio and test failsafe with props off. A wrong flash is not a crash by itself; a wrong failsafe after a flash is.

If you want the hardware picture of where this code sits, open the schema plate. If you want to feel a mixer before you buy a board, use the browser trainer – it is a school loop, not a flashed FC.