View source for Contiki

{{Short description|Real-time operating system}}
{{About|the embedded operating system}}
{{Distinguish|Kon-Tiki}}
{{ infobox OS
| name                   = Contiki
| screenshot             = Contiki-ipv6-rpl-cooja-simulation.png
| caption                = Screenshot of an Ubuntu system showing Contiki 2.6 running on 41 nodes forming an IPv6-RPL-6LoWPAN network in the Cooja Contiki network simulator.
| developer              = [[Adam Dunkels]]
| source model           = [[Open-source software|Open source]]
| released               = {{Start date and age|2003|03|10|df=yes}}
| latest release version = 3.0
| latest release date    = {{Start date and age|2015|08|25|df=yes}}
| license                = [[BSD-3-Clause]]
| discontinued           = yes
| website                = {{URL|www.contiki-os.org}}
| repo                   = {{URL|github.com/contiki-os/contiki}}
}}
{{Infobox software
| name                   = Contiki-NG
| developer =
| latest release version = 5.0
| latest release date    = {{Start date and age|2024|12|30}}
| repo                   = {{URL|github.com/contiki-ng/contiki-ng}}
| website                = {{URL|www.contiki-ng.org}}
| discontinued           = no
}}
'''Contiki''' is an [[operating system]] for networked, memory-constrained systems with a focus on low-power wireless [[Internet of Things]] (IoT) devices. Contiki is used for systems for [[street light]]ing, sound monitoring for [[smart cities]], [[radiation monitoring]] and alarms.<ref name=primary>{{Citation |url= http://www.contiki-os.org/ |title= Contiki OS}}.</ref> It is [[open-source software]] released under the [[BSD licenses|BSD-3-Clause]] license.

Contiki was created by [[Adam Dunkels]] in 2002<ref>{{Citation |title= Contiki: Bringing IP to Sensor Networks |url= http://ercim-news.ercim.eu/en76/rd/contiki-bringing-ip-to-sensor-networks}}</ref> and has been further developed by a worldwide team of developers from Texas Instruments, Atmel, Cisco, [[ENEA (Italy)|ENEA]], [[ETH Zurich]], Redwire, [[RWTH Aachen University]], Oxford University, SAP, Sensinode, [[Swedish Institute of Computer Science]], ST Microelectronics, Zolertia, and many others.<ref>{{Citation |url= http://www.contiki-os.org/community.html |title= Contiki OS |contribution= Community}}.</ref> Contiki gained popularity because of its built in TCP/IP stack and lightweight [[preemption (computing)|preemptive scheduling]] over [[Event-driven architecture|event-driven]] [[kernel (operating system)|kernel]]<ref>{{Citation |first= Adam |last= Dunkels |contribution= Contiki – a lightweight and flexible operating system for tiny networked sensors |title= Proceedings of the 29th Annual IEEE International Conference on Local Computer Networks. |pages= 455–462 |year=2004}}.</ref> which is a very motivating feature for IoT. The name ''Contiki'' comes from [[Thor Heyerdahl]]'s famous [[Kon-Tiki]] raft.

Contiki provides multitasking and a built-in [[Internet Protocol Suite]] (TCP/IP stack), yet needs only about 10 [[kilobyte]]s of [[random-access memory]] (RAM) and 30 kilobytes of [[read-only memory]] (ROM).<ref name=primary /> A full system, including a [[graphical user interface]], needs about 30 kilobytes of RAM.<ref>[https://www.wired.com/2014/06/contiki/ Out in the Open: The Little-Known Open Source OS That Rules the Internet of Things]</ref>

A new branch has recently been created, known as [http://contiki-ng.org/ Contiki-NG]: The OS for Next Generation IoT Devices

==Hardware==
Contiki is designed to run on types of hardware devices that are severely constrained in [[random-access memory|memory]], [[Electric power|power]], processing power, and communication [[Bandwidth (computing)|bandwidth]]. A typical Contiki system has memory on the order of kilobytes, a power budget on the order of milliwatts, processing speed measured in megaHertz, and communication bandwidth on the order of hundreds of kilobits/second. Such systems include many types of [[embedded system]]s, and old [[8-bit]] computers.

==Networking==
Contiki provides three network mechanisms: the [[uIP (micro IP)|uIP]] TCP/IP stack,<ref>{{Citation |first= Adam |last= Dunkels |contribution= Full TCP/IP for 8 Bit Architectures |title= Proceedings of the First ACM/Usenix International Conference on Mobile Systems, Applications and Services (MobiSys) |place= San Francisco |date=May 2003}}</ref> which provides [[IPv4]] networking, the uIPv6 stack,<ref>{{Citation |first1= Mathilde |last1= Durvy |first2= Julien |last2= Abeillé |first3= Patrick |last3= Wetterwald |first4= Colin |last4= O'Flynn |first5= Blake |last5= Leverett |first6= Eric |last6= Gnoske |first7= Michael |last7= Vidales |first8= Geoff |last8= Mulligan |first9= Nicolas |last9= Tsiftes |first10= Niclas |last10= Finne |first11= Adam |last11= Dunkels |contribution= Making sensor networks IPv6 ready |title= Proceedings of the Sixth ACM Conference on Networked Embedded Sensor Systems (SenSys) |publisher= ACM |type= poster session |place= Raleigh, [[North Carolina|NC]], [[United States of America|US]] |date=November 2008}}</ref> which provides [[IPv6]] networking, and the Rime stack, which is a set of custom lightweight networking protocols designed for low-power wireless networks. The IPv6 stack was contributed by Cisco and was, when released, the smallest IPv6 stack to receive the ''IPv6 Ready'' certification.<ref>{{Citation |publisher= Cisco |title= Newsroom |year= 2008 |url= http://newsroom.cisco.com/dlls/2008/prod_101408e.html}}.</ref> The IPv6 stack also contains the ''[[IPv6 Routing Protocol for Low-Power and Lossy Networks|Routing Protocol for Low power and Lossy Networks]]'' (RPL) routing protocol for low-power lossy IPv6 networks and the [[6LoWPAN]] header compression and adaptation layer for [[IEEE 802.15.4]] links.

Rime is an alternative network stack, for use when the overhead of the IPv4 or IPv6 stacks is prohibitive. The Rime stack provides a set of communication primitives for low-power wireless systems. The default primitives are single-hop unicast, single-hop broadcast, multi-hop unicast, network flooding, and address-free data collection. The primitives can be used on their own or combined to form more complex protocols and mechanisms.<ref>{{Citation |first1= Adam |last1= Dunkels |first2= Fredrik |last2= Österlind |first3= Zhitao |last3= He |contribution= An adaptive communication architecture for wireless sensor networks |title= Proceedings of the Fifth ACM Conference on Networked Embedded Sensor Systems (SenSys) |place= Sydney, [[Australia|AU]] |date=November 2007}}.</ref>

==Low-power operation==
Many Contiki systems are severely power-constrained. Battery operated wireless sensors may need to provide years of unattended operation and with little means to recharge or replace batteries. Contiki provides a set of mechanisms to reduce the power consumption of systems on which it runs. The default mechanism for attaining low-power operation of the radio is called ContikiMAC.<ref>{{Citation |title= The ContikiMAC Radio Duty Cycling Protocol |first= Adam |last= Dunkels |url= http://dunkels.com/adam/dunkels11contikimac.pdf}}.</ref> With ContikiMAC, nodes can be running in low-power mode and still be able to receive and relay radio messages.

==Simulation==
The Contiki system includes a sensor simulator called Cooja, which simulates Contiki nodes.<ref>{{Citation |title= Contiki OS |contribution= Start |url= http://www.contiki-os.org/start.html}}.</ref> The nodes belong to one of the three following classes: a) emulated Cooja nodes, b) Contiki code compiled and executed on the simulation host, or c) Java nodes, where the behavior of the node must be reimplemented as a Java class. One Cooja simulation may contain a mix of sensor nodes from any of the three classes. Emulated nodes can also be used to include non-Contiki nodes in a simulated network.

In Contiki 2.6, platforms with the [[TI MSP430]] and [[Atmel AVR]] microcontrollers can be emulated.

==Programming model==
To run efficiently on small-memory systems, the Contiki programming model is based on [[protothreads]].<ref>{{Citation |first1= Adam |last1= Dunkels |first2= Oliver |last2= Schmidt |first3= Thiemo |last3= Voigt |first4= Muneeb |last4= Ali |contribution= Protothreads: Simplifying event-driven programming of memory-constrained embedded systems |title= Proceedings of the Fourth ACM Conference on Embedded Networked Sensor Systems (SenSys) |place= Boulder, [[Colorado|CO]], USA |date=November 2006}} {{Cite book |doi= 10.1145/1182807.1182811| chapter= Protothreads| title= Proceedings of the 4th international conference on Embedded networked sensor systems - Sen ''Sys'' '06| pages= 29| year= 2006| last1= Dunkels |first1= A. |last2= Schmidt |first2= O. |last3= Voigt |first3= T. |last4= Ali |first4= M. |isbn= 1595933433| s2cid= 983128}} ([http://dunkels.com/adam/dunkels06protothreads.pdf PDF], [http://dunkels.com/adam/dunkels06protothreads.ppt Presentation slides]).</ref><ref>{{Citation |title= Code |url= http://code.google.com/p/protothread/ |contribution= Protothread }}.</ref> A protothread is a memory-efficient programming abstraction that shares features of both [[Multithreading (software)|multithreading]] and [[event-driven programming]] to attain a low memory overhead of each protothread. The kernel invokes the protothread of a process in response to an internal or external event. Examples of internal events are timers that fire or messages being posted from other processes. Examples of external events are sensors that trigger or incoming packets from a radio neighbor.

Protothreads are cooperatively scheduled. Thus, a Contiki process must always explicitly yield control back to the kernel at regular intervals. Contiki processes may use a special protothread construct to block waiting for events while yielding control to the kernel between each event invocation.

== Features ==
[[Image:Contiki-avr.png|300px|thumb|Screenshot of the [[Virtual Network Computing|VNC]] server running on the [[Atmel AVR]] port of Contiki]]

Contiki supports per-process optional preemptive multithreading, [[inter-process communication]] using message passing through events, as well as an optional [[graphical user interface]] (GUI) subsystem with either direct graphic support for locally connected terminals or networked virtual display with [[Virtual Network Computing]] (VNC) or over Telnet.

A full installation of Contiki includes the following features:
* Multitasking kernel
* Optional per-application [[Preemption (computing)|preemptive multithreading]]
* [[Protothread]]s
* [[Internet protocol suite|Internet Protocol Suite]] (TCP/IP) [[computer network|networking]], including [[IPv6]]
* [[Windowing system]] and GUI
* Networked remote display using [[Virtual Network Computing]]
* A [[web browser]] (claimed to be the world's smallest)
* Personal [[web server]]
* Simple [[telnet]] client
* [[Screensaver]]

Contiki is supported by popular [[Transport Layer Security|SSL/TLS]] libraries such as [[wolfSSL]], which includes a port in its 3.15.5 release.<ref>{{Cite web|url=https://www.wolfssl.com/wolfssl-contiki-os-port/|title=wolfSSL CONTIKI OS port - wolfSSL|date=2018-12-18|language=en-US|access-date=2019-01-09}}</ref>

== Ports ==
[[Image:Contiki-C64.png|thumb|Contiki on the Commodore 64]]

=== Microcontrollers===
* [[Atmel]] – [[ARM architecture family|ARM]], [[Atmel AVR|AVR]]
* [[NXP Semiconductors]] – LPC1768,<ref>{{Cite web|url=https://sourceforge.net/p/contiki/mailman/message/31753844/|title = The Contiki Operating System / &#91;Contiki-developers&#93; Contiki port for the LPC1768 arm processor| date=19 December 2020 }}</ref> LPC2103, MC13224
* [[Microchip Technology|Microchip]] – [[PIC microcontroller|dsPIC, PIC32]] (PIC32MX795F512L)
* [[Texas Instruments]] – [[TI MSP430|MSP430]], CC2430, CC2538, CC2630, CC2650, CC2538: cctv, Firefly, Zoul  (comprises the CC2538 and CC1200 in a single module format)
* [[STMicroelectronics]] – [[STM32#STM32 W|STM32 W]]

=== Computers===
* [[Apple II]]<ref group= "lower-alpha" name="cc65">[[cc65]] based development</ref>
* [[Atari 8-bit computers]]<ref group= "lower-alpha" name="cc65" />
* [[Atari ST]]
* [[Atari Portfolio]]
* [[Pocket Viewer]]
* [[Commodore PET]]<ref group= "lower-alpha" name="cc65" />
* [[VIC-20]],<ref group= "lower-alpha" name="cc65" />
* [[Commodore 64]],<ref group= "lower-alpha" name="cc65" /> [[Commodore 128]]<ref group= "lower-alpha" name="cc65" />
* [[Oric computers|Oric]]<ref group= "lower-alpha" name="cc65" />
* [[NEC PC-6001]]
* [[Sharp Wizard]]
* [[x86]]-based [[Unix-like]] systems, atop [[GTK+]], or more directly using an [[X Window System]]<ref>{{Citation |archive-url= https://web.archive.org/web/20031209140045/http://hstein.trix.net/contiki/ |publisher= Trix |title= Running Contiki under Windows |archive-date= 2003-12-09 |url= http://hstein.trix.net/contiki/ |first= H |last= Stein}}.</ref>

=== Game consoles===
* [[GP32]]
* [[Game Boy]]
* [[Game Boy Advance]]
* [[Atari Jaguar|Jaguar]]
* [[Nintendo Entertainment System]]<ref group= "lower-alpha" name="cc65" />
* [[TurboGrafx-16]]<ref group= "lower-alpha" name="cc65" />

== See also ==
{{Portal |Open-source software}}
* [[BeRTOS]]
* [[ERIKA Enterprise]]
* [[Nano-RK]]
* [[RIOT (operating system)|RIOT]]
* [[SymbOS]]
* [[TinyOS]]
* [[Comparison of real-time operating systems]]

== Notes ==
{{Reflist |group= "lower-alpha"}}

==References==
{{Reflist |30em}}
{{refbegin}}
* {{Citation |url= http://hitmen.c02.at/html/tools_contiki.html |publisher= C02 |place= [[Austria|AT]] |title= Hitmen |contribution= Tools Contiki }}: unofficial website for historic ports of the 1.x version.
* {{Citation |url=http://www.manishshakya.com.np/index.php/page/code |contribution=Minimal Contiki OS for LPC2103 |title=Manishshakya |place=NP |url-status=dead |archive-url=https://web.archive.org/web/20140604192611/http://www.manishshakya.com.np/index.php/page/code |archive-date=2014-06-04 }}.
* {{Citation |url= http://a2retrosystems.com/contiki.html |title= Contiki 2.5 config file and disk image generator |publisher= A2 retro systems }}.
* {{Citation |url= http://rtn.sssup.it/index.php/software/contiki |title= Contiki porting on PIC32 (Seed-Eye Board) |publisher= SSSUP |place= [[Italy|IT]] |access-date= 2013-01-31 |archive-url= https://web.archive.org/web/20130318052656/http://rtn.sssup.it/index.php/software/contiki |archive-date= 2013-03-18 |url-status= dead }}.
{{refend}}

==External links==
{{Commons category|Contiki}}
* {{Official website|www.contiki-os.org}}
{{Wireless Sensor Network}}
{{Real-time operating systems}}

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