This is mostly untouched from the original documentation. It does not really belong to “quickstart”. Also, this needs cleanup.

Directory Structure

This is included for reference, and it’s not necessary to know all the details at first.

The general directory layout for NuttX is very similar to the directory structure of the Linux kernel – at least at the most superficial layers. At the top level is the main makefile and a series of sub-directories identified below and discussed in the following paragraphs:

Configuration Files. The NuttX configuration consists of logic in processor architecture directories, chip/SoC directories, and board configuration directories. The complete configuration is specified by several settings in the NuttX configuration file.

  • Processor architecture specific files. These are the files contained in the arch/<arch-name>/ directory and are discussed in a paragraph below. As an example, all ARM processor architectures are provided under the arch/arm/ directory which is selected with the CONFIG_ARCH="arm" configuration option.

    Variants of the processor architecture may be provided in sub-directories of the Extending this example, the ARMv7-M ARM family is supported by logic in arch/arm/include/armv7-m and arch/arm/src/armv7-m directories which are selected by the CONFIG_ARCH_CORTEXM3=y, CONFIG_ARCH_CORTEXM4=y, or CONFIG_ARCH_CORTEXM7=y configuration options

  • Chip/SoC specific files. Each processor architecture is embedded in a System-on-a-Chip (SoC) architecture. The full SoC architecture includes the processor architecture plus chip-specific interrupt logic, clocking logic, general purpose I/O (GPIO) logic, and specialized, internal peripherals (such as UARTs, USB, etc.).

    These chip-specific files are contained within chip-specific sub-directories also under the arch/<arch-name>/ directory and are selected via the CONFIG_ARCH_CHIP selection.

    As an example, the STMicro STM32 SoC architecture is based on the ARMv7-M processor and is supported by logic in the arch/arm/include/stm32 and arch/arm/src/stm32 directories which are selected with the CONFIG_ARCH_CHIP="stm32" configuration setting.

  • Board specific configurations. In order to be usable, the chip must be contained in a board environment. The board configuration defines additional properties of the board including such things as peripheral LEDs, external peripherals (such as networks, USB, etc.).

    These board-specific configuration files can be found in the boards/<arch-name>/<chip-name>/<board-name>/ sub-directories and are discussed in a paragraph below.

    The directory boards/arm/stm32/stm32f4disovery/, as an example, holds board-specific logic for the STM32F4 Discovery board and is selected via the CONFIG_ARCH_BOARD="stm32f4discovery" configuration setting.


This directory holds the NuttX documentation. It’s made with the Sphinx documentation system. See the file for information on how to build it.


This sub-directory holds the NuttX supported architectures.

For details see Architecture-Specific Code.


The binfmt/ subdirectory contains logic for loading binaries in the file system into memory in a form that can be used to execute them.


The audio/ subdirectory contains the NuttX audio sub-system.


The boards/ subdirectory contains custom logic and board configuration data for each board. These board-specific configurations plus the architecture-specific configurations in the arch/ subdirectory complete define a customized port of NuttX.

Boards Subdirectory Structure

The boards/ directory contains board specific configuration files. Each board must provide a sub-directory <board-name> under boards/<arch-name>/<chip-name>/.

See Boards Support for details.


This sub-directory holds the NuttX CMake functions.

For details see CMake Support.


This sub-directory holds the NuttX cryptographic sub-system.

For details see Crypto API Subsystem.


This directory holds architecture-independent device drivers.

For details see Device Drivers.


This directory contains the NuttX file system. This file system is described below.


This directory contains files for graphics/video support under NuttX.

For details see NX Graphics Subsystem.


This directory holds NuttX header files. Standard header files file retained in can be included in the normal fashion:


This directory holds a collection of standard libc-like functions with custom interfaces into NuttX.

For details see NuttX libraries.


This is the NuttX memory manager.

For details see Memory Management.


This directory contains the implementation of the NuttX networking layer including internal socket APIs.

For details see Network Support.


This directory contains OpenAMP support for NuttX.

For details see OpenAMP Support.




The files forming core of the NuttX RTOS reside here.


If NuttX is built as a separately compiled kernel (with CONFIG_BUILD_PROTECTED=y or CONFIG_BUILD_KERNEL=y), then the contents of this directory are built. This directory holds a syscall interface that can be used for communication between user-mode applications and the kernel-mode RTOS.

For details see Syscall Layer.


This directory holds a collection of tools and scripts to simplify configuring, building and maintaining NuttX.

Refer to the /tools Host Tools page for more information about the individual files. Some of these tools are discussed below as well in the discussion of configuring and building NuttX.


This directory holds support for video sub-system.

For details see Video Subsystem.


This directory holds support for hardware-independent wireless support.

For details see Wireless Subsystem.


The top-level CMakeLists.txt file.


The top-level Makefile in the $(TOPDIR) directory contains all of the top-level control logic to build NuttX.