# Pixhawk Series

[Pixhawk®](https://pixhawk.org/) is an independent open-hardware project providing readily-available, low-cost, and high-end, _autopilot hardware designs_ to the academic, hobby and industrial communities.

Pixhawk is the reference hardware platform for PX4, and runs PX4 on the [NuttX](https://nuttx.apache.org/) OS.

Manufacturers have created many different boards based on the open designs, with form factors that are optimised for applications from cargo carrying though to first person view (FPV) racers.

:::tip For computationally intensive tasks (e.g. computer vision) you will need a separate companion computer (e.g. [Raspberry Pi 2/3 Navio2](autopilot_experimental/raspberry_pi_navio2)) or a platform with an integrated companion solution. :::

## Key Benefits

Key benefits of using a _Pixhawk series_ controller include:

* Software support - as PX4 reference hardware these are our best-maintained boards.
* Flexibility in terms of hardware peripherals that can be attached.
* High quality.
* Highly customizable in terms of form factor.
* Widely-used and thus well-tested/stable.
* Automated update of latest firmware via _QGroundControl_ (end-user friendly).

## Supported Boards

The PX4 Project uses [Pixhawk Standard Autopilots](autopilot_pixhawk_standard) as reference hardware. These are the controllers that are fully compatible with the Pixhawk standard (including use of trademarks) and that are still being manufactured.

:::note The PX4 maintenance and test teams maintain and support these standard boards. :::

Pixhawk-like boards that are not fully compliant with the specification may be [manufacturer-supported](autopilot_manufacturer_supported), [experimental/discontinued](autopilot_experimental), or unsupported.

The rest of this topic explains a bit more about the Pixhawk series, but is not required reading.

## Background

The [Pixhawk project](https://pixhawk.org/) creates open hardware designs in the form of schematics, which define a set of components (CPU, sensors, etc.) and their connections/pin mappings.

Manufacturers are encouraged to take the [open designs](https://github.com/pixhawk/Hardware) and create products that are best suited to a particular market or use case (the physical layout/form factor not part of the open specification). Boards based on the same design are binary compatible.

:::note While a physical connector standard is not mandated, newer products generally follow the [Pixhawk Connector Standard](https://pixhawk.org/pixhawk-connector-standard/). :::

The project also creates reference autopilot boards based on the open designs, and shares them under the same [licence](#licensing-and-trademarks).

### FMU Versions

The Pixhawk project has created a number of different open designs/schematics. All boards based on a design should be binary compatible (run the same firmware).

Each design is named using the designation: FMUvX (e.g.: FMUv1, FMUv2, FMUv3, FMUv4, etc.). Higher FMU numbers indicate that the board is more recent, but may not indicate increased capability (versions can be almost identical - differing only in connector wiring).

PX4 _users_ generally do not need to know very much about FMU versions:

* _QGroundControl_ automatically downloads the correct firmware for a connected autopilot (based on its FMU version "under the hood").
* Choosing a controller is usually based on physical constraints/form factor rather than FMU version.

:::note The exception is that if you're using FMUv2 firmware it is [limited to 1MB of flash](silicon_errata#fmuv2-pixhawk-silicon-errata). In order to fit PX4 into this limited space, many modules are disabled by default. You may find that some [parameters are missing](../../../advanced_config/parameters#missing) and that some hardware does not work "out of the box". :::

PX4 _developers_ need to know the FMU version of their board, as this is required to build custom hardware.

At very high level, the main differences are:

* **FMUv2:** Single board with STM32427VI processor ([Pixhawk 1 (Discontinued)](autopilot_discontinued/pixhawk), [pix32](autopilot_discontinued/holybro_pix32), [Pixfalcon](autopilot_discontinued/pixfalcon), [Drotek DroPix](autopilot_discontinued/dropix))
* **FMUv3:** Identical to FMUv2, but usable flash doubled to 2MB ([Hex Cube Black](autopilot_pixhawk_standard/pixhawk-2),[CUAV Pixhack v3](autopilot_manufacturer_supported/pixhack_v3),[mRo Pixhawk](autopilot_pixhawk_standard/mro_pixhawk), [Pixhawk Mini (Discontinued)](autopilot_pixhawk_standard/pixhawk_mini))
* **FMUv4:** Increased RAM. Faster CPU. More serial ports. No IO processor ([Pixracer](autopilot_pixhawk_standard/pixracer))
* **FMUv4-PRO:** Slightly increased RAM. More serial ports. IO processor ([Pixhawk 3 Pro](autopilot_pixhawk_standard/pixhawk3_pro))
* **FMUv5:** New processor (F7). Much faster. More RAM. More CAN buses. Much more configurable. ([Pixhawk 4](autopilot_pixhawk_standard/pixhawk4),[CUAV v5](autopilot_discontinued/cuav_v5),[CUAV V5+](autopilot_manufacturer_supported/cuav_v5_plus),[CUAV V5 nano](autopilot_manufacturer_supported/cuav_v5_nano))
* **FMUv5X:** New processor (F7). Much faster, Modular design. More reliable. More Redundancy. More RAM. More CAN buses. Much more configurable & customizable .([Pixhawk 5X](autopilot_pixhawk_standard/pixhawk5x), Skynode)

### Licensing and Trademarks

Pixhawk project schematics and reference designs are licensed under [CC BY-SA 3](https://creativecommons.org/licenses/by-sa/3.0/legalcode).

The license allows you to use, sell, share, modify and build on the files in almost any way you like - provided that you give credit/attribution, and that you share any changes that you make under the same open source license (see the [human readable version of the license](https://creativecommons.org/licenses/by-sa/3.0/) for a concise summary of the rights and obligations).

:::note Boards that are _derived directly_ from Pixhawk project schematic files (or reference boards) must be open sourced. They can't be commercially licensed as proprietary products. :::

Manufacturers can create (compatible) _fully independent products_ by first generating fresh schematic files that have the same pin mapping/components as the FMU designs. Products that are based on independently created schematics are considered original works, and can be licensed as required.

Product names/brands can also be trademarked. Trademarked names may not be used without the permission of the owner.

:::tip _Pixhawk_ is a trademark, and cannot be used in product names without permission. :::

## Additional Information

### LEDs

All _Pixhawk-series_ flight controllers support:

* A user facing RGB _UI LED_ to indicate the current _readiness to fly_ status of the vehicle. This is typically a superbright I2C peripheral, which may or may not be mounted on the board (i.e. FMUv4 does not have one on board and typically uses an LED mounted on the GPS).
* Three _Status LE&#x44;_&#x73; that provide lower level power status, bootloader mode and activity, and error information.

To interpret the LEDs see: [LED Meanings](../../getting_started/vehicle_status/led_meanings).
