Zephyr (operating system): Difference between revisions

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{{Short description|Real-time operating system}}

{{Infobox OS

| name = Zephyr

| logo = Zephyr RTOS logo 2015.svg

| logo = <!-- filename only (no wikilink, no Image:/File:) -->

| logo size =

| logo caption = Zephyr Project = logo

| logo alt =

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| developer = [[Linux Foundation]],<br />[[Wind River Systems]]

| collapsible =

| family = [[Real-time operating system]]s

| version of = <!-- For articles about releases of operating systems ONLY -->

| working state = Current

| developer = [[Linux Foundation]], [[Wind River Systems]]

| source model = [[Open source]]

| family = [[Real-time operating system]]s

| released = {{Start date and age|2016|07|26|df=yes}}<ref name="zephyr-project" />

| working state = Current

| latest release version = 4.2.0

| source model = Open source

| latest release date = {{Start date and age|2025|07|19|df=yes}}<ref>{{cite web |url= https://github.com/zephyrproject-rtos/zephyr/releases/tag/v4.2.0 |title= Zephyr v4.2.0|website= [[GitHub]]}}</ref><ref>{{cite web |url=https://www.zephyrproject.org/zephyr-rtos-4-2-now-available-introduces-renesas-rx-support-usb-video-class-and-more|title= Zephyr RTOS 4.2 Now Available|website= [[Zephyr blog]]}}</ref>

| released = {{Start date and age|2016|02|17}}<ref name="zephyr-project" />

| marketing target = [[Internet of things]], [[embedded system]]s

| discontinued = <!-- DON'T use this for articles about releases of operating systems -->

| programmed in = [[C (programming language)|C]]

| RTM date = <!-- {{Start date and age|YYYY|MM|DD|df=yes/no}} ONLY for articles about OS releases -->

| language = English

| GA date = <!-- {{Start date and age|YYYY|MM|DD|df=yes/no}} ONLY for articles about OS releases -->

| update model = <!-- APT, Windows Update, etc. -->

| latest release version = 1.6.0

| package manager = <!-- dpkg, rpm, Windows installer, etc. -->

| latest release date = {{Start date and age|2016|12|15}} <ref>{{cite web|url=https://www.zephyrproject.org/community/blog/announcing-zephyr-os-v160|title=Announcing Zephyr OS v1.6.0|publisher=}}</ref>

| supported platforms = [[ARM architecture|ARM]] ([[Cortex-M]], [[ARM Cortex-R|Cortex-R]], [[Cortex-A]]), [[ARC (processor)|ARC]], [[MIPS architecture|MIPS]], [[Nios II]], [[RISC-V]], [[Tensilica|Xtensa]], [[SPARC]], [[x86]], [[x86-64]]

| latest preview version =

| kernel type = [[Microkernel]] (pre-v1.6)<ref name="NanoMicrokernel"/><ref name="Monolithic1"/><ref name="Monolithic2"/><br />[[Monolithic kernel|Monolithic]] (v1.6+)<ref name="Monolithic1"/><ref name="Monolithic2"/>

| latest preview date = <!-- {{Start date and age|YYYY|MM|DD|df=yes/no}} -->

| userland =

| marketing target =

| ui =

| programmed in =

| license = [[Apache License|Apache 2.0]]

| language = <!-- Supported human languages (English, French, Italian, Arabic, ...) -->

| preceded by = Wind River Rocket

| update model = <!-- APT, Windows Update, etc. -->

| succeeded by =

| package manager = <!-- dpkg, rpm, Windows installer, etc. -->

| other articles =

| supported platforms = [[ARM architecture|ARM]] ([[ARM Cortex-M3|Cortex-M3]], [[ARM Cortex-M4|Cortex-M4]]), [[x86 architecture|x86]], [[ARC (processor)|ARC]], [[RISC-V]], [[Nios II]]

| kernel type = Micro/Nanokernel

| userland =

| ui =

| license = [[Apache License 2.0]]

| preceded by =

| succeeded by =

| website = {{URL|http://www.zephyrproject.org/}}

| support status = <!-- For articles about releases of operating systems ONLY -->

| other articles =

}}

'''Zephyr''' ({{IPAc-en|ˈ|z|ɛ|f|_|ə|r}}) is a small [[real-time operating system]] (RTOS)<ref>{{Cite news|url=http://linuxgizmos.com/zephyr-a-tiny-open-source-iot-rtos/|title=Meet Linux's little brother: Zephyr, a tiny open-source IoT RTOS|date=2016-02-17|work=LinuxGizmos.com|access-date=2018-02-23|language=en-US}}</ref> for connected, resource-constrained and [[embedded device]]s (with an emphasis on [[microcontroller]]s) supporting multiple architectures and released under the [[Apache License]] 2.0. Zephyr includes a [[Kernel (operating system)|kernel]], and all components and [[Library (computing)|libraries]], [[device driver]]s, [[protocol stack]]s, [[file system]]s, and [[firmware update]]s, needed to develop full [[application software]].<ref name="docs.zephyrproject.org">{{Cite web |url=https://docs.zephyrproject.org/latest/introduction/ |title=Zephyr Project documentation: Introduction |language=en}}</ref>

It is named after [[Zephyrus]], the ancient Greek god of the west wind.<ref>{{Cite web|url=https://docs.zephyrproject.org/latest/develop/west/index.html#west-name|title=West (Zephyr's meta-tool) — Zephyr Project Documentation|website=docs.zephyrproject.org}}</ref>

'''Zephyr''' is a small [[real-time operating system]]<ref>http://linuxgizmos.com/zephyr-a-tiny-open-source-iot-rtos/</ref> for connected, resource-constrained devices supporting multiple architectures and released under the [[Apache License 2.0]] (a BSD licensed fork can be found in the [[Arduino]] 101 software source package from Intel).<ref name="1.0.0-release-notes">[https://www.zephyrproject.org/content/zephyr-kernel-v100-release-notes Zephyr Kernel v1.0.0 Release Notes]</ref>

== History ==

Zephyr originated from Virtuoso RTOS for [[digital signal processor]]s (DSPs).<ref name="zp19">{{cite web |last=Clarysse |first=Ivo |date=November 22, 2019 |url=https://www.zephyrproject.org/zephyr-an-operating-system-for-iot/ |title=Zephyr – An Operating System for IoT |website=Zephyr Project}}</ref><ref name="eej"/> In 2001, [[Wind River Systems]] acquired Belgian software company Eonic Systems, the developer of Virtuoso. In November 2015, Wind River Systems renamed the [[operating system]] to ''Rocket'', made it open-source and royalty-free.<ref name="eej">{{Cite news |last=Turley |first=Jim |date=25 November 2015 |url=http://www.eejournal.com/archives/articles/20151125-windriver/ |title=Wind River Sets Rocket RTOS on Free Trajectory |website=Electronic Engineering Journal |publisher=Techfocus Media |language=en-US |access-date=2018-02-23}}</ref> Compared to Wind River's other RTOS, [[VxWorks]], Rocket had much smaller memory needs, especially suitable for sensors and single-function embedded devices. Rocket could fit into as little as 4 KB of memory, while VxWorks needed 200 KB or more.<ref name="eej"/>

In November 2015 it was originally developed as Rocket<ref>http://windriver.com/products/operating-systems/rocket/</ref><ref>http://www.eejournal.com/archives/articles/20151125-windriver/</ref><ref>https://software.intel.com/en-us/iot/rocket</ref> kernel by [[Wind River Systems]] for [[Internet of Things]] devices<ref name="patel-zephyr-project">Niheer Patel: [http://blogs.windriver.com/wind_river_blog/2016/02/wind-river-welcomes-linux-foundations-zephyr-project.html Wind River Welcomes Linux Foundation’s Zephyr Project], Wind River Systems, 17 February 2016</ref>

In February 2016, ZephyrRocket became a hosted collaborative project of the [[Linux Foundation]] under the name ''Zephyr''.<ref name="zp19"/><ref name=":0">{{Cite news |last=Guerrini |first=Federico |date=2016-02-19 |url=httphttps://www.forbes.com/sites/federicoguerrini/2016/02/19/the-internet-of-things-goes-open-source-with-linux-foundations-zephyr-project/ |title=The Internet Ofof Things Goes Open Source Withwith Linux Foundation's Zephyr Project|last=Guerrini|first=Federico|date=2016-02-19 |work=|newspaper=[[Forbes]] |access-date=2017-01-12|via=}}</ref><ref name="zephyr-project">Zephyr{{Cite Project:web [|url=https://www.zephyrproject.org/news/linux-foundation-announces-project-build-real-time-operating-system-internet-things-devices |title=The Linux Foundation Announces Project to Build Real-Time Operating System for Internet of Things Devices], |author=<!-- Human name. --> |date=17 February 2016 |website=Zephyr Project |publisher=Linux Foundation |archiveurl=https://web.archive.org/web/20160310073146/https://www.zephyrproject.org/news/linux-foundation-announces-project-build-real-time-operating-system-internet-things-devices |archivedate=2016-03-10}}</ref> Wind River Systems contributed the Rocket kernel to Zephyr, but still provided Rocket to its clients, charging them for the cloud services.<ref name="patel-zephyr-project"/><ref name="eej"/> As a result, Rocket became "essentially the commercial version of Zephyr".<ref name="patel-zephyr-project">{{Cite web |url=http://blogs.windriver.com/wind_river_blog/2016/02/wind-river-welcomes-linux-foundations-zephyr-project.html |title=Wind River Welcomes Linux Foundation's Zephyr Project |last=Patel |first=Niheer |date=17 February 2016 |website=Wind River Systems |access-date=18 February 2016 |archive-date=21 February 2016 |archive-url=https://web.archive.org/web/20160221003830/http://blogs.windriver.com/wind_river_blog/2016/02/wind-river-welcomes-linux-foundations-zephyr-project.html |url-status=dead }}</ref>

Since then, early members and supporters of Zephyr include [[Intel]], [[NXP Semiconductors]], [[Synopsys]], and UbiquiOS Technology[[Linaro]],<ref>{{Cite webnews |last=Osborne |first=Charlie |date=2016-02-19 |url=httphttps://www.zdnet.com/article/the-linux-foundations-zephyr-project-building-an-operating-system-for-iot-devices/ |title=The Linux Foundation's Zephyr Project: A custom operating system for IoT devices {{!}} ZDNet|last=Osborne|first=Charlie|date=2016-02-19|website=[[ZDNet]] |publisher=[[CBS Interactive]] |access-date=2017-01-12}}</ref> [[Texas Instruments]], [[Nordic Semiconductor]], [[Oticon]], and [[Bose Corporation|Bose]].<ref>{{Cite web |url=https://www.zephyrproject.org/project-members/|title=Project Members|website=Zephyr Project}}</ref>

{{As of|2025|01}}, Zephyr had the largest number of contributors and commits compared to other RTOSes (including [[Mbed]], [[RT-Thread]], [[NuttX]], and [[RIOT (operating system)|RIOT]]).<ref>{{Cite web |url=https://github.com/zephyrproject-rtos/zephyr |title=Zephyr GitHub page |website=[[GitHub]] |date=January 30, 2025}}</ref>

== Features ==

==Features==

The Zephyr Kernel is a small-footprint kernel designed for use on resource-constrained systems: from simple embedded environmental sensors and LED wearables to sophisticated smart watches and IoT wireless gateways.

Zephyr intends to provide all components needed to develop resource-constrained and embedded or microcontroller-based applications. This includes:<ref name="docs.zephyrproject.org"/>

* A small kernel

* A flexible configuration and build system for compile-time definition of required resources and modules

* A set of protocol stacks ([[IPv4]] and [[IPv6]], [[Constrained Application Protocol]] (CoAP), [[OMA LWM2M|LwM2M]], [[MQTT]], [[802.15.4]], [[Thread (network protocol)|Thread]], [[Bluetooth Low Energy]], [[CAN bus|CAN]])

* A virtual file system interface with several flash file systems for non-volatile storage ([[FatFs]], LittleFS, NVS)

* Management and device [[firmware update]] mechanisms

===Configuration and build system===

The Zephyr Kernel offers a number of features that distinguish it from other small-footprint OSes:

Zephyr uses [[Kconfig]] and [[devicetree]] as its configuration systems, inherited from the [[Linux kernel]], but implemented in [[Python (programming language)|Python]] programming language for portability to non-[[Unix]] operating systems.<ref>{{Cite web |url=https://github.com/zephyrproject-rtos/zephyr/tree/master/scripts |title=scripts/ folder |website=[[GitHub]] |date=12 May 2020}}</ref> The RTOS build system is based on [[CMake]], which allows Zephyr applications to be built on [[Linux]], [[macOS]], and [[Microsoft Windows]].<ref>{{Cite web |url=https://docs.zephyrproject.org/latest/application/ |title=Application Development: Zephyr Project Documentation |website=Zephyr Project}}</ref>

===''West'' utility tool===

* Single address-space OS.

Zephyr has a general-purpose tool called ''West'' for managing repositories, downloading programs to hardware, etc.

* Highly configurable.

* Resources defined at compile-time.

* Minimal error checking.

* Development services.

=== Security Kernel===

Early Zephyr kernels used a dual [[Microkernel|nanokernel plus microkernel]] design.<ref name="NanoMicrokernel">{{Cite web |last=Wasserman |first=Shawn |date=February 22, 2016 |url=https://mobile.engineering.com/amp/11530.html |title=How Linux's IoT Zephyr Operating System Works |website=Engineering.com}}</ref><ref name="Monolithic1">{{Cite web |last=Helm |first=Maureen |date=December 15, 2016 |url=https://www.zephyrproject.org/announcing-zephyr-os-v1-6-0/ |title=Announcing Zephyr OS v1.6.0 |website=Zephyr Project}}</ref><ref name="Monolithic2">{{Cite web |last=Wong |first=William G. |date=July 6, 2017 |url=https://www.electronicdesign.com/technologies/embedded-revolution/article/21805266/zephyr-a-wearable-operating-system |title=Zephyr: A Wearable Operating System |website=[[Electronic Design]]}}</ref> In December 2016, with Zephyr 1.6, this changed to a [[monolithic kernel]].<ref name="Monolithic1"/><ref name="Monolithic2"/>

A group is dedicated to maintaining and improving the security.<ref>{{Cite web|url=http://www.techrepublic.com/article/linux-foundation-announces-zephyr-project-an-open-source-iot-operating-system/|title=Linux Foundation announces Zephyr Project, an open source IoT operating system - TechRepublic|last=Wallen|first=Jack|date=2016-02-18|website=[[TechRepublic]]|publisher=[[CBS Interactive]]|access-date=2017-01-12}}</ref> Also being owned and supported by a community means the eyes of the world's open source developers are vetting the code. Which significantly increase Zephyr security.<ref name=":0" />

The kernel offers several features that distinguish it from other small OSes:<ref name="docs.zephyrproject.org"/>

=== Single address-space OS ===

* [[Single address space operating system|Single address space]]

* Multiple scheduling algorithms

* Highly configurable and modular for flexibility, with resources defined at compile-time

* [[Memory protection unit]] (MPU) based protection

* [[Asymmetric multiprocessing]] (AMP, based on OpenAMP) and [[symmetric multiprocessing]] (SMP) support

===Security===

Combines application-specific code with a custom kernel to create a monolithic image that gets loaded and executed on a system’s hardware. Both the application code and kernel code execute in a single shared address space.

A group is dedicated to maintaining and improving the security.<ref>{{Cite news |last=Wallen |first=Jack |date=2016-02-18 |url=http://www.techrepublic.com/article/linux-foundation-announces-zephyr-project-an-open-source-iot-operating-system/ |title=Linux Foundation announces Zephyr Project, an open source IoT operating system |website=[[TechRepublic]] |publisher=[[CBS Interactive]] |access-date=2017-01-12}}</ref> Also, being owned and supported by a community means the world's open source developers are vetting the code, which significantly increases security.<ref name=":0" />

=== Highly configurable ===

Allows an application to incorporate only the capabilities it needs as it needs them, and to specify their quantity and size.

=== Resources defined at compile-time ===

Requires all system resources be defined at compilation time, which reduces code size and increases performance.

=== Minimal error checking ===

Provides minimal run-time error checking to reduce code size and increase performance. An optional error-checking infrastructure is provided to assist in debugging during application development.

=== Development services ===

Development services offering a number of familiar services for development:

1. Multi-threading services for both priority-based, non-preemptive cooperative threads and priority-based, preemptive threads with optional round robin time-slicing.

2. Interrupt services for both compile-time and run-time registration of interrupt handlers.

3. Inter-thread synchronization services for binary semaphores, counting semaphores, and mutex semaphores.

4. Inter-thread data passing services for basic message queues, enhanced message queues, and byte streams.

5. Memory allocation services for dynamic allocation and freeing of fixed-size or variable-size memory blocks.

6. Power management services such as tickless idle and an advanced idling infrastructure.

==See also==

* [[Embedded operating system]]

==References==

{{Reflist}}

<references />

== External links ==

*[http://www.zephyrproject.org/ Official website]

{{Real-time operating systems}}

{{Linux Foundation}}

[[Category:Real-timeARM operating systems]]

[[Category:Embedded operating systems]]

[[Category:Free software operating systems]]

[[Category:Software using the Apache license]]

[[Category:Linux Foundation projects]]

[[Category:MicrokernelReal-basedtime operating systems]]

[[Category:ARMSoftware operatingusing systemsthe Apache license]]

[[Category:OperatingIA-32 systemoperating stubssystems]]

[[Category:X86-64 operating systems]]

[[Category:MIPS operating systems]]