> For the complete documentation index, see [llms.txt](https://px4.gitbook.io/px4-user-guide/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://px4.gitbook.io/px4-user-guide/development/hardware/porting_guide/porting_guide_nuttx.md).

# NuttX Board Porting Guide

In order to port PX4 on NuttX to a new hardware target, that hardware target must be supported by NuttX. The NuttX project maintains an excellent [porting guide](https://cwiki.apache.org/confluence/display/NUTTX/Porting+Guide) for porting NuttX to a new computing platform.

The following guide assumes you are using an already supported hardware target or have ported NuttX (including the [PX4 base layer](https://github.com/PX4/PX4-Autopilot/tree/main/platforms/nuttx/src/px4)) already.

The configuration files for all boards, including linker scripts and other required settings, are located under [/boards](https://github.com/PX4/PX4-Autopilot/tree/main/boards/) in a vendor- and board-specific directory (i.e. **boards/*****VENDOR*****/*****MODEL*****/**)).

The following example uses FMUv5 as it is a recent [reference configuration](/px4-user-guide/development/hardware/reference_design.md) for NuttX based flight controllers:

* Running `make px4_fmu-v5_default` from the **PX4-Autopilot** directory will build the FMUv5 config
* The base FMUv5 configuration files are located in: [/boards/px4/fmu-v5](https://github.com/PX4/PX4-Autopilot/tree/main/boards/px4/fmu-v5).
  * Board specific header (NuttX pins and clock configuration): [/boards/px4/fmu-v5/nuttx-config/include/board.h](https://github.com/PX4/PX4-Autopilot/blob/main/boards/px4/fmu-v5/nuttx-config/include/board.h).
  * Board specific header (PX4 configuration): [/boards/px4/fmu-v5/src/board\_config.h](https://github.com/PX4/PX4-Autopilot/blob/main/boards/px4/fmu-v5/src/board_config.h).
  * NuttX OS config (created with NuttX menuconfig): [/boards/px4/fmu-v5/nuttx-config/nsh/defconfig](https://github.com/PX4/PX4-Autopilot/blob/main/boards/px4/fmu-v5/nuttx-config/nsh/defconfig).
  * Build configuration: [boards/px4/fmu-v5/default.px4board](https://github.com/PX4/PX4-Autopilot/blob/main/boards/px4/fmu-v5/default.px4board).

## NuttX Menuconfig Setup

To modify the NuttX OS configuration, you can use [menuconfig](https://bitbucket.org/patacongo/nuttx/src/master/) using the PX4 shortcuts:

```sh
make px4_fmu-v5_default menuconfig
make px4_fmu-v5_default qconfig
```

For fresh installs of PX4 onto Ubuntu using [ubuntu.sh](https://github.com/PX4/PX4-Autopilot/blob/main/Tools/setup/ubuntu.sh) you will also need to install *kconfig* tools from [NuttX tools](https://bitbucket.org/nuttx/tools/src/master/).

:::note The following steps are not required if using the [px4-dev-nuttx](https://hub.docker.com/r/px4io/px4-dev-nuttx/) docker container or have installed to macOS using our normal instructions (as these include`kconfig-mconf`). :::

Run the following commands from any directory:

```sh
git clone https://bitbucket.org/nuttx/tools.git
cd tools/kconfig-frontends
sudo apt install gperf
./configure --enable-mconf --disable-nconf --disable-gconf --enable-qconf --prefix=/usr
make
sudo make install
```

The `--prefix=/usr` determines the specific installation location (which must be in the `PATH` environment variable). The `--enable-mconf` and `--enable-qconf` options will enable the `menuconfig` and `qconfig` options respectively.

To run `qconfig` you may need to install additional Qt dependencies.

### Bootloader

First you will need a bootloader, which depends on the hardware target:

* STM32H7: the bootloader is based on NuttX, and is included in the PX4 Firmware. See [here](https://github.com/PX4/PX4-Autopilot/tree/main/boards/holybro/durandal-v1/nuttx-config/bootloader) for an example.
* For all other targets, <https://github.com/PX4/Bootloader> is used. See [here](https://github.com/PX4/Bootloader/pull/155/files) for an example how to add a new target. Then checkout the [building and flashing instructions](/px4-user-guide/development/advanced/stm32_bootloader.md).

### Firmware Porting Steps

1. Make sure you have a working [development setup](/px4-user-guide/development/getting_started/dev_env.md) and installed the NuttX menuconfig tool (see above).
2. Download the source code and make sure you can build an existing target:

   ```bash
   git clone --recursive https://github.com/PX4/PX4-Autopilot.git
   cd PX4-Autopilot
   make px4_fmu-v5
   ```
3. Find an existing target that uses the same (or a closely related) CPU type and copy it. For example for STM32F7:

   ```bash
   mkdir boards/manufacturer
   cp -r boards/px4/fmu-v5 boards/manufacturer/my-target-v1
   ```

   Change **manufacturer** to the manufacturer name and **my-target-v1** to your board name.

Next you need to go through all files under **boards/manufacturer/my-target-v1** and update them according to your board.

1. **firmware.prototype**: update the board ID and name
2. **default.px4board**: update the **VENDOR** and **MODEL** to match the directory names (**my-target-v1**). Configure the serial ports.
3. Configure NuttX (**defconfig**) via `make manufacturer_my-target-v1 menuconfig`: Adjust the CPU and chip, configure the peripherals (UART's, SPI, I2C, ADC).
4. **nuttx-config/include/board.h**: Configure the NuttX pins. For all peripherals with multiple pin options, NuttX needs to know the pin. They are defined in the chip-specific pinmap header file, for example [stm32f74xx75xx\_pinmap.h](https://github.com/PX4/NuttX/blob/px4_firmware_nuttx-8.2/arch/arm/src/stm32f7/hardware/stm32f74xx75xx_pinmap.h).
5. **src**: go through all files under **src** and update them as needed, in particular **board\_config.h**.
6. **init/rc.board\_sensors**: start the sensors that are attached to the board.