Transcript The Contiki Operating System

The Contiki Operating System
Jack Nosek
History
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Developed by Adam Dunkels of SICS
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Also developed protothreads and μIP
First released on March 10, 2003
Named after Thor Heyerdahl's famous
Kon-Tiki raft
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“Contiki runs on tiny and prehistoric
computers, yet is able to do much of what
we expect from large and modern
computers.”
Who uses it?
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Most common application is as an OS
for Networks of Embedded Systems
Hobbyists use it as an OS for older
and smaller systems
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Ports for Apple II, Atari, Gameboy, NES,
Commodore 64 and 128
Screen captures at
http://www.sics.se/~adam/contiki/ports/i
ndex.html
Features
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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
Event Driven Kernel
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Kernel is event based making it a
real time OS
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An event triggers the kernel to call the
corresponding event handler
Functions very similar to TinyOS
Has its drawbacks, i.e. long running
computations
TCP/IP Stack Support
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Implements Dunkels’s own TCP/IP
stack called μIP
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Memory Requirements
Kilobytes of Program Code
 Hundreds of bytes of RAM
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Allows to connect to networks using
SLIP (Serial Line IP)
Dynamic Program Loading
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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
Small Memory Requirements
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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
Protothreads
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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.
Event-driven
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Event-driven
(TinyOS)
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Processes do not run
without events
Event occurs: kernel Kernel
invokes event
handler
Event handler runs
to completion
(explicit return;)
Handler
Handler
Handler
Handler
Contiki: implementing threads on top
of an event-based kernel
Event
Event
Kernel
Event
Event
Thread
Thread
Contiki Programs
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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.
End
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Works Cited
Slides 10 and 11 Taken from
Adam Dunkles Presentation
Contiki – a Lightweight and Flexible
Operating System for Tiny
Networked Sensors
found at
http://www.sics.se/~adam/slides/contikiemnets.ppt