NuttX
NuttX is a real-time operating system with an emphasis on technical standards compliance and small size. Scalable from 8-bit to 64-bit microcontroller environments, the main governing standards in NuttX are from the Portable Operating System Interface and the American National Standards Institute. Further standard application programming interfaces from Unix and other common RTOSes are adopted for functions unavailable under these standards, or inappropriate for deeply embedded environments, such as a fork.
NuttX was first released in 2007 by Gregory Nutt as free and open-source software under the permissive BSD license. It is currently undergoing incubation at The Apache Software Foundation.
Implementation
NuttX is written almost exclusively in the programming language C and uses Kconfig to configure and generate GNU makefiles for the system. The program distribution combines the kernel and a substantial amount of middleware and code for board support and device drivers. The kernel and much of the other code was written by the original author, Gregory Nutt. He maintains the source code exclusively, and must approve all community contributions.Key features
- Standards compliant
- Core task management
- Modular design
- Fully preemptible
- Naturally scalable
- Highly configurable
- Easily extensible to new processor architectures, SoC architecture, or board architectures
- Scheduling: first in, first out and round-robin
- Real-time, deterministic, with support for priority inheritance
- Tickless operation
- POSIX/ANSI-like task controls, named message queues, counting semaphores, clocks/timers, signals, POSIX Threads, environment variables
- Multiple file systems
- VxWorks-like task management and watchdog timers
- BSD socket interface
- Extensions to manage preemption
- Optional tasks with address environments
- Symmetric multiprocessing
- Loadable kernel modules
- Memory configurations: flat embedded build, protected build with MPU, and kernel build with MMU
- Memory allocators: standard heap memory allocation, granule allocator, shared memory, and dynamically sized, per-process heaps
- Thread local storage
- Inheritable controlling terminals, pseudoterminals and input/output redirection
- On-demand paging
- System logging
- May be built either as an open, flat embedded RTOS or as a separately built, secure kernel with a system call gate interface
- Built-in, per-thread CPU load measurements
- Custom NuttX C library
Supported platforms
- ARM
- * ARM7TDMI
- * ARM920T
- * ARM926EJS
- * ARM Cortex-A5
- * ARM Cortex-A8
- * ARM Cortex-A9
- * ARM Cortex-R4/R4F
- * ARM Cortex-M0
- * ARM Cortex-M3
- * ARM Cortex-M4
- * ARM Cortex-M7
- Atmel AVR
- * Atmel 8-bit AVR
- * AVR32
- Freescale M68HCS12
- Intel
- * 80x86
- MIPS
- * MicroChip PIC32MX
- * MicroChip PIC32MZ
- Misoc
- * LM32
- OpenRISC
- * mor1kx
- Renesas/Hitachi
- * Renesas/Hitachi SuperH
- * Renesas M16C/26
- RISC-V
- * NEXT RISC-V NR5Mxx
- * GreenWaves GAP8
- Xtensa LX6
- * Expressif ESP32
- Zilog
- * Zilog Z16F
- * Zilog eZ80 Acclaim!
- * Zilog Z8Encore!
- * Zilog Z80
File system
- Tiny in-memory, root pseudo-file-system
- Virtual file system
- Mountable volumes. Bind mountpoint, file system, and block device driver
- Generic system logging support
- File Allocation Table 12/16/32 file system support
- Network File System client, supports NFS, version 3, UDP
- NXFFS: a tiny wear-leveling flash memory file system
- SMART: flash file system from Ken Pettit
- Generic driver for SPI-based cards: MultiMediaCard and Secure Digital
- Romfs file system support
- BINFS pseudo-file system support
- HOSTFS file system support
- Union file system: supports combining and overlaying file systems
- PROCFS pseudo-file system
- A Binary Loader with support for the following formats:
- * Separately linked Executable and Linkable Format modules
- * Separately linked modules for NXFLAT: a binary format that can be XIP from a file system
- PATH variable support
- File transfers via TFTP and FTP, HTML, and Zmodem
- Intel HEX conversions
Device drivers
- VFS supports character and block drivers
- Asynchronous I/O
- Network, USB, USB, serial, I2C, I2S, NAND, Controller Area Network, ADC, DAC, PWM, Quadrature Encoder, and watchdog timer driver architectures
- RAM drive or disk, pipes, FIFO, /dev/null, /dev/zero drivers
- Generic driver for SPI-based or SDIO-based MMC/SD/SDH cards
- Power management subsystem
- 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
- Cryptographic subsystem
- Input devices: touchscreen, USB keyboard, USB mouse, GPIO-based buttons and keypads
- Memory technology devices
- Analog devices: support for analog-to-digital converter, digital-to-analog converter, multiplexers, and amplifiers
- System logging devices
- Porting guide
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 supporting input/output , strings, Standard Template Library, run-time type information, exceptions, etc.
Networking
- Multiple network interface support; multiple network link layer support
- IPv4, IPv6,Internet protocol suite, User Datagram Protocol, Internet Control Message Protocol, Internet Group Management Protocol version 2 stacks
- Stream and datagram sockets
- Raw socket and local, Unix domain socket support
- DNS name resolution, NetDB
- IEEE 802.11 FullMac
- IEEE 802.15.4 MAC + 6loWPAN
- Serial Line Internet Protocol, TUN/PPP, local loopback devices
- A cJSON port
- Small size
- BSD compatible socket layer
- Networking utilities server and client, Simple Mail Transfer Protocol client, Telnet client, File Transfer Protocol server and client, Trivial File Transfer Protocol client, Hypertext Transfer Protocol server and client, Network Time Protocol ; inheritable Telnet sessions. VNC server
- Network File System client, supports NFS, version 3, UDP
- ICMPv6 autonomous auto-configuration
- A NuttX port of Jef Poskanzer's thttpd HTTP server integrated with NXFLAT to provide embedded CGI
- PHY link status management
- UDP network discovery, XML RPC server
- XML RPC server
- Support for network modules
Flash support
- Memory Technology Device inspired interface for MTD devices
- FTL: simple flash Translation Layer support file systems on Flash
- NAND Support
- NXFFS: a wear-leveling flash memory file system
- Support for Serial Peripheral Interface bus based flash devices
USB support
Host
- USB host architecture for USB host controller drivers and device-dependent USB class drivers.
- USB host controller drivers available for the Atmel SAMA5Dx, NXP LPC17xx, LPC31xx, and STmicro STM32.
- Device-dependent USB class drivers available for USB mass storage and HID keyboard.
- Seamless support for USB hubs.
Device
- Gadget-like architecture for USB device controller drivers and device-dependent USB class drivers
- USB device controller drivers available for the PIC32, Atmel AVR, SAM3, SAM4, and SAMA5Dx, NXP LPC17xx, LPC214x, LPC313x, and LPC43xx, Silicon Laboraties EFM32, STMicro STM32 F1, F2, F3, and F4, 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
- Framebuffer drivers
- Liquid-crystal display drivers for both parallel and SPI LCDs and organic light-emitting diode
- Segment LCD drivers
- VNC Server
- NX Graphics Subsystem: A graphics library, windowing system, and font support that works with either framebuffer or LCD drivers
- NuttX Widgets: A graphical user interface written in conservative C++ that integrates with NX graphics
- NuttX window manager: tiny, based on the NX graphics subsystem and NuttX widgets
Projects using it
- Thingsee Internet of things development device.
- PX4 autopilot uses NuttX to control a variety of autonomous platforms.
- Biffer Board supports many RTOSs including NuttX.
- MP3 player implemented with NuttX.
- OsmocomBB uses NuttX to develop an operating system for cell phones.
- A homebrew steer-by-wire system implemented using NuttX.
- Video Performance Measurement Device.
- Low Power Embedded Software Optimization for the NuttX RTOS.
- Motorola Moto Z.
- Sony uses NuttX in their audio processors.
- Samsung announces TizenRT based on NuttX RTOS.