How to Code on TinyOS

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How to Code on TinyOS

• Xufei Mao
• Advisor Dr. Xiang-yang Li
• CS Dept. IIT

2
Outlines

• What is TinyOS?
• Hardware Software
• NesC
• A simple example
• Conclusion

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So why do we need a new OS?
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Traditional OS

• Huge !
• Multi-threaded architecture gtlarge memory
• I/O model
• Kernel and user space separation
• Typically no energy constraints
• Ample available resources

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Sensor Hardware Constraints

• Lower Power
• Limited memory
• Slow CPU
• Size (Small)
• Limited hardware parallelisms
• Communication using radio
• Low-bandwidth
• Short range

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Desired OS Properties

• Small memory footprint
• Efficient in power and computation
• Communication is fundamental
• Real-time
• Support diverse application design

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TinyOS Solution

• Concurrency uses event-driven architecture
• Modularity
• Application composed of components
• OS Application compiles into single executable
• Communication
• Uses event/command model
• FIFO and non pre-emptive scheduling
• No kernel/application boundary

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The Hardware
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Software

• TinyOS (Platform)
• Coding language
• NesC (Network Embedded System C)

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TinyOS Memory Model

• STATIC memory allocation!
• No heap (malloc)
• No function pointers
• No dynamic, run-time allocation
• Global variables
• Available on a per-frame basis
• Conserve memory
• Use pointers
• Local variables
• Saved on the stack
• Declared within a method

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TinyOS nesC Concepts

• New Language nesC. Basic unit of code
  Component
• Component
• Process Commands
• Throws Events
• Has a Frame for storing local state
• Uses Tasks for concurrency
• Components provide interfaces
• Used by other components to communicate with this
  component

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Components

• Two type of components
• Module
• component written with code
• Configuration
• components wired together

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Components
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TinyOS Application (Sample)
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Commands/Events/Tasks

• Commands
• Should be non-blocking i.e. take parameters start
  the processing and return to app
• postpone time-consuming work by posting a task
• Can call commands on other components
• Events
• Can call commands, signal other events, post
  tasks but cannot be signal-ed by commands
• Pre-empt tasks, not vice-versa
• Tasks
• FIFO scheduling
• Non pre-emptable by other task, pre-emtable by
  events
• Used to perform computationally intensive work
• Can be posted by commands and/or events

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nesC

• Naming conventions
• nesC files extension .nc
• Clock.nc either an interface (or a
  configuration)
• ClockC.nc a configuration
• ClockM.nc a module

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nesC Keywords
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nesC Keywords -implementation
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Interfaces
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Modules

• Implement one or more interfaces
• Can use one or more other interfaces

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Modules (Sample)
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Configurations

• Two components are linked together in nesC by
  wiring them
• Interfaces on user component are wired to the
  same interface on the provider component
• 3 wiring statements in nesC
• endpoint1 endpoint2
• endpoint1 -gt endpoint2
• endpoint1 lt- endpoint2 (equivalent endpoint2 -gt
  endpoint1)

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Configurations (Sample)
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nesC Wiring Syntax
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Compile Run

• Compiler processes nesC files converting them
  into a gigantic C file
• Has both your application the relevant OS
  components you are using
• Then platform specific compiler compiles this C
  file
• Becomes a single executable
• Loader installs the code onto the Mote (Mica2,
  Telos, etc.)

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Simple Example 1

• Blink Application
• Blink.nc configuration

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Simple Example 1

• Blink Application
• BlinkM.nc module

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Simple Example 2

• Communication between two sensors
• Environment Xubuntu TinyOS 2.0
• Hardware TelosB sensors

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Resources

• Gauravs TinyOS-1.x installation howto
• http//www.cs.umass.edu/gmathur/misc/tinyos_setup
  .htm
• Tinyos-2.x installation howto (straightforward)
• http//www.tinyos.net/tinyos-2.x/doc/html/install-
  tinyos.html
• The official TinyOS tutorial (pretty good)
• http//www.tinyos.net/tinyos-1.x/doc/tutorial/
• The offical TinyOS-2.x tutorial (very good)
• http//www.tinyos.net/tinyos-2.x/doc/html/tutorial
  /index.html
• nesC http//nescc.sourceforge.net/

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Resources

• Other Docs
• nesC paper http//none.cs.umass.edu/gmathur/tiny
  os/nesc-pldi-2003.pdf
• nesC manual http//none.cs.umass.edu/gmathur/tin
  yos/nesc-ref.pdf
• TinyOS abstractions http//none.cs.umass.edu/gma
  thur/tinyos/tinyosnsdi04.pdf

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Reference

• TinyOS Tutorial by Jeremy Gummeson, Sensors Lab,
  UMass-Amherst
• TinyOS Programming by Philip Levis
• nesC paper http//none.cs.umass.edu/gmathur/tiny
  os/nesc-pldi-2003.pdf

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Conclusion