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The Contiki Operating System

The Contiki Operating System. Jack Nosek. History. Developed by Adam Dunkels of SICS Also developed protothreads and μ IP First released on March 10, 2003 Named after Thor Heyerdahl's famous Kon-Tiki raft

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The Contiki Operating System

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  1. The Contiki Operating System Jack Nosek

  2. History • Developed by Adam Dunkels of SICS • Also developed protothreads and μIP • First released on March 10, 2003 • Named after Thor Heyerdahl's famous Kon-Tiki raft • “Contiki runs on tiny and prehistoric computers, yet is able to do much of what we expect from large and modern computers.”

  3. Who uses it? • Most common application is as an OS for Networks of Embedded Systems • Hobbyists use it as an OS for older and smaller systems • Ports for Apple II, Atari, Gameboy, NES, Commodore 64 and 128 • Screen captures at http://www.sics.se/~adam/contiki/ports/index.html

  4. Features • Minimalist Event Driven Kernel, even runs on 8-bit Microcontrollers • TCP/IP Stack Support • Dynamic Loading and Unloading of Programs • Small Memory Requirements • Optional Preemptive Multithreading through Protothreads

  5. Event Driven Kernel • Kernel is event based making it a real time OS • An event triggers the kernel to call the corresponding event handler • Functions very similar to TinyOS • Has its drawbacks, i.e. long running computations

  6. TCP/IP Stack Support • Implements Dunkels’s own TCP/IP stack called μIP • Memory Requirements • Kilobytes of Program Code • Hundreds of bytes of RAM • Allows to connect to networks using SLIP (Serial Line IP)

  7. Dynamic Program Loading • The Core Code and Program Code are kept separate in ROM. • Program Code loaded at runtime. • Program code can be loaded from ROM or RAM • Allows for “Over the Air Programming” for networks of sensors

  8. Small Memory Requirements • The base system, providing multitasking and TCP/IP networking, can be compiled in about 32 KB • Smallest system to date uses about 2000 bytes of RAM • Jack Ganssle praised Contiki for its low memory usage in his Embedded Muse newsletter, #113

  9. Protothreads • Implemented as an additional library on top of the event based kernel • Stackless, lightweight thread comprised of a single C function using 2 bytes of RAM to record its state • Adds a layer of abstraction to the state-machine event based code usually written, to create a sequential flow of program code.

  10. Event-driven Handler • Event-driven (TinyOS) • Processes do not run without events • Event occurs: kernel invokes event handler • Event handler runs to completion (explicit return;) Handler Kernel Handler Handler

  11. Contiki: implementing threads on top of an event-based kernel Event Thread Thread Event Kernel Event Event

  12. Contiki Programs • Contiki Tool-kit (CTK) GUI • Virtual Network Computing (VNC) Server • A Web Server • A Web Browser • A command line shell. • A telnet server. • An IRC client. • An FTP client. • A disk directory file reader. • A file and disk image downloader utility. • A simple desktop calculator.

  13. End • Works Cited • Slides 10 and 11 Taken fromAdam Dunkles Presentation Contiki – a Lightweight and Flexible Operating System for TinyNetworked Sensorsfound at http://www.sics.se/~adam/slides/contiki-emnets.ppt

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