NuttX Real-Time Operating System

NuttX is a real-time operating system (RTOS) with an emphasis on standards compliance and small footprint. Scalable from 8-bit to 32-bit microcontroller environments, the primary governing standards in NuttX are Posix and ANSI standards. Additional standard APIs from Unix and other common RTOS's (such as VxWorks) are adopted for functionality not available under these standards, or for functionality that is not appropriate for deeply-embedded environments (such as fork()).

NuttX was first released in 2007 by Gregory Nutt under the permissive BSD license.

Key features

  • Standards Compliant.
  • Core Task Management.
  • Modular design.
  • Fully pre-emptible.
  • Naturally scalable.
  • Highly configurable.
  • Easily extensible to new processor architectures, SoC architecture, or board architectures. See Porting Guide.
  • FIFO and round-robin scheduling.
  • Realtime, deterministic, with support for priority inheritance.
  • Tickless operation.
  • POSIX/ANSI-like task controls, named message queues, counting semaphores, clocks/timers, signals, pthreads, environment variables, filesystem.
  • VxWorks-like task management and watchdog timers.
  • BSD socket interface.
  • Extensions to manage pre-emption.
  • Optional tasks with address environments (Processes).
  • Memory Configurations: (1) Flat embedded build, (2) Protected build with MPU, and (3) Kernel build with MMU.
  • Memory Allocators: (1) standard heap memory allocation, (2) granule allocator, (3) shared memory, and (4) dynamically sized, per-process heaps.
  • Inheritable “controlling terminals” and I/O redirection
  • On-demand paging.
  • System logging
  • May be built either as an open, flat embedded RTOS or as a separtely built, secure micro-kernel with a system call interface.
  • Built-in, per-thread CPU load measurements.
  • Well documented in the NuttX User Guide.

Supported platforms

  • ARM
    • ARM7TDMI (TI TMS320 C6571, Calyspo, NXP LPC214x, LPC2378, STMicro STR71x)
    • ARM920T (Freescale i.MX1)
    • ARM926EJS (TI DM320, NXP LPC31xx)
    • ARM Cortex-A5 (Atmel SAMA5D3, SAMA5D4)
    • ARM Cortex-A8 (Allwinner A10)
    • ARM Cortex-M0 (nuvoTon NUC120, Freescale KL25Z, KL26Z)
    • ARM Cortex-M3 (ST Micro STM32 F1/F2/F3, TI/Stellaris LM3S, NXP LPC17xx, Atmel SAM3U/3X, SiliconLabs EFM32)
    • ARM Cortex-M4 (with/without floating point unit: ST Micro STM32 F4, TI/Stellaris LM4F/TM4C, NXP LPC43xx, Freescale Kinetis K40/60, Atmel SAM4C/4E/4S/4L)
    • ARM Cortex-M7 (Atmel SAMV7)
  • Atmel AVR
    • Atmel 8-bit AVR (AT90USB, ATmega)
    • AVR32
  • Freescale M68HCS12
  • Intel
    • 80c52
    • 80×86
  • MIPS
    • MicroChip PIC32MX (MIPS32 24Kc)
    • MicroChip PIC32MZ (MIPS32 M14k)
  • Renesas/Hitachi
    • Renesas/Hitachi SuperH
    • Renesas M16C/26
  • Zilog
    • Zilog Z16F
    • Zilog eZ80 Acclaim!
    • Zilog Z8Encore!
    • Zilog Z80

File system

  • Tiny in-memory, root pseudo-file-system.
  • Virtual File System (VFS)
  • Mount-able volumes. Bind mountpoint, filesystem, and block device driver.
  • Generic system logging (SYSLOG) support.
  • FAT12/16/32 filesystem support.
  • NFS Client. Client side support for a Network File System (NFS, version 3, UDP).
  • NXFFS. The tiny NuttX wear-leveling FLASH file system.
  • SMART. FLASH file system from Ken Pettit.
  • procfs/ file system.
  • Generic driver for SPI-based MMC/SD/SDH cards.
  • ROMFS filesystem support.
  • A Binary Loader with support for the following formats:
    • Separately linked ELF modules.
    • Separately linked NXFLATmodules. NXFLAT is a binary format that can be XIP from a file system.
  • PATH variable support.
  • File transfers via TFTP and FTP (get and put), HTML (wget), and Zmodem (sz and rz).
  • Intel HEX conversions.

Device Drivers

  • VFS supports character and block drivers.
  • Asynchronous I/O (AIO).
  • Network, USB (host), USB (device), serial, I2C, I2S, NAND, CAN, ADC, DAC, PWM, Quadrature Encoder, and watchdog timer driver architectures.
  • RAMDISK, pipes, FIFO, /dev/null, /dev/zero drivers.
  • Generic driver for SPI-based or SDIO-based MMC/SD/SDH cards.
  • Power Management sub-system.
  • ModBus support provided by built-in FreeModBus version 1.5.0.
  • Graphics Devices: framebuffer drivers, graphic and segment LCD drivers
  • Audio Subsystem: CODECs, audio input and output drivers. Command line and graphic media player applications.
  • Input Devices: Touchscreen, USB keyboard, USB mouse, GPIO-based buttons and keypads.
  • Analog Devices: Support for Analog-to-Digital conversion (ADC), Digital-to-Analog conversion (DAC), multiplexers, and amplifiers.

C/C++ Library

  • Standard C Library Fully integrated into the OS.
  • Includes floating point support via a Standard Math Library.
  • Add-on uClibc++ module provides Standard C++ Library supportng iostreams, strings, STL, RTTI, exceptions, etc. (LGPL).


  • Multiple network interface support; multiple network link layer support
  • IPv4, IPv6, TCP/IP, UDP, ICMP, IGMPv2 (client) stacks.
  • Stream and datagram sockets
  • Raw socket and local, Unix domain socket support
  • SLIP
  • A cJSON port
  • Small footprint (based on uIP).
  • BSD compatible socket layer.
  • Networking utilities (DHCP server and client, SMTP client, TELNET client, FTP server and client, TFTP client, HTTP server and client, NTP client). Inheritable TELNET sessions (as “controlling terminal”).
  • ICMPv6 autonomous auto-configuration
  • NFS Client. Client side support for a Network File System (NFS, version 3, UDP).
  • A NuttX port of Jeff Poskanzer's THTTPD HTTP server integrated with NXFLAT to provide embedded CGI.
  • PHY Link Status Management
  • UDP Network Discvory, XML RPC Server.
  • XML RPC Server
  • Support for network modules (such as the TI CC3000 WLAN module).

Flash Support

  • MTD-inspired interface for Memory Technology Devices.
  • NAND Support.
  • FTL. Simple Flash Translation Layer support file systems on FLASH.
  • NXFFS. the NuttX wear-leveling FLASH file system.
  • Support for SPI-based FLASH devices.

USB Support

USB Host Support

  • USB host architecture for USB host controller drivers and device-dependent USB class drivers.
  • USB host controller drivers available for the NXP LPC17xx.
  • Device-dependent USB class drivers available for USB mass storage and HID keyboard.

USB Device Support

  • Gadget-like architecture for USB device controller drivers and device-dependent USB class drivers.
  • USB device controller drivers available for the PIC32, NXP LPC17xx, LPC214x, LPC313x, LPC43xx, STMicro STM32F1x, STM32F2x, STM32F4x) and TI DM320.
  • Device-dependent USB class drivers available for USB serial and for USB mass storage.
  • Built-in USB trace functionality for USB debug.

Graphics Support



A small, scalable, bash-like shell for NuttX with rich feature set and small footprint. See the NuttShell User Guide.

Pascal Runtime

The Pascal add-on is available for download from the SourceForge website.