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 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) already.

The configuration files for all boards, including linker scripts and other required settings, are located under /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 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.

  • Board specific header (NuttX pins and clock configuration): /boards/px4/fmu-v5/nuttx-config/include/board.h.

  • Board specific header (PX4 configuration): /boards/px4/fmu-v5/src/board_config.h.

  • NuttX OS config (created with NuttX menuconfig): /boards/px4/fmu-v5/nuttx-config/nsh/defconfig.

  • Build configuration: boards/px4/fmu-v5/default.px4board.

NuttX Menuconfig Setup

To modify the NuttX OS configuration, you can use menuconfig using the PX4 shortcuts:

make px4_fmu-v5_default menuconfig
make px4_fmu-v5_default qconfig

For fresh installs of PX4 onto Ubuntu using ubuntu.sh you will also need to install kconfig tools from NuttX tools.

:::note The following steps are not required if using the px4-dev-nuttx docker container or have installed to macOS using our normal instructions (as these includekconfig-mconf). :::

Run the following commands from any directory:

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 for an example.

• For all other targets, https://github.com/PX4/Bootloader is used. See here for an example how to add a new target. Then checkout the building and flashing instructions.

Firmware Porting Steps

1. Make sure you have a working development setup and installed the NuttX menuconfig tool (see above).

2. Download the source code and make sure you can build an existing target:

   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:

   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.

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.