TinyOS

Overview
 Need

of TinyOS
 Market Target of TinyOS - WSNs
 What is TinyOS?
 Features of TinyOS
 TinyOS Structure
 TinyOS design models
 TinyOS Basic Constructs
 The nesC Language

Need of TinyOS


Problems with traditional OS :
 Multithreaded Architecture not useful
 Large Memory Footprint
 Does not help to conserve energy and power



Requirements for Wireless Sensor Networks :
 Efficient utilization of energy and power
 Small Footprint and support diversity in design
usage

Market Target of TinyOS


Wireless Sensor Network (Market Target
of TinyOS)

Wireless sensor networks mainly use broadcast
communication.Wireless sensing + Data
networking.
 Consist of sensor networks which have – Low
power, limited memory, energy constrained due to
small size.
 Large no. of heterogeneous sensor node devices
spread over a large field. Consist of sensors which
are distributed in an ad hoc manner.


Typical architecture of sensor node

What is TinyOS?
TinyOS is a free open source operating system.
 Designed for wireless sensor networks.
 TinyOS began as a collaboration between
University of California, Berkeley and Intel
Research.
 An embedded operating system written in nesC
language.
 It features a component based architecture.


TinyOS Design Models
 Component-based

model

(modularity)
Simple functions are incorporated in
components with clean interfaces;



Complex functions can be implemented
by composing components.



TinyOS Design Models
 Event-based model
 Interact with outside by events (no command
shell)
 There
•

•

are two kinds of events for TinyOS:
External events: Clock events and message
events;
Internal events: triggered by external events.

Features of TinyOS


Completely non-blocking



Programs are built out of software components.



Tasks are non-preemptive and run in FIFO
order.



TinyOS code is statically linked.

TinyOS as a Solution







Component based architecture allows frequent
changes while still keeping the size of code
minimum.
Event based execution model means no user/kernel
boundary and hence supports high concurrency.
It is power efficient as it makes the sensors sleep as
soon as possible.
Has small footprint as it uses a non-preemptable
FIFO task scheduling.

TinyOS Models
Data

Model
Thread Model
Programming Model
Component Model
Network Model

Data Memory Model


Static Memory Allocation
• No Heaps or any other dynamic structures used.
• Memory requirements determined at compile
time.
• This increases the runtime efficiency.
 Global variables
• Allocated on per frame basis.
 Local Variables
• Saved on the stack
• Defined in the function/method

Thread Model
 Power-Aware Two-levels Scheduling
Long running tasks and interrupt events
 Sleep unless tasks in queue, wakeup on event
 Tasks
 Time-flexible, background jobs
 Atomic with respect to other tasks
 Can be preempted by events
 Events
 Time-critical, shorter duration
 Last-in first-out semantic (no priority)
 Can post tasks for deferred execution


Programming Model





Separation construction/composition
Construction of Modules
 Modules implementation similar to C coding
 Programs are built out of components
 Each component specifies an interface
 Interfaces are “hooks” for wiring components
Composition of Configurations
 Components are statically wired together
 Increases programming efficiency (code reuse)
an runtime efficiency.

Component Model


Components should use and provide
bidirectional interfaces.



Components should call and implement
commands and signal and handle events.



Components must handle events of used
interfaces and also provide interfaces that
must implement commands.

TinyOS Basic Constructs
 Commands


Cause actions to be initiated

 Events





Small amount of processing to be done in a timely
manner
E.g. timer, ADC interrupts
Notify that action has occurred.
Can interrupt longer running tasks

TinyOS Basic Constructs
 Tasks





Background Computation
Not time critical
Larger amount of processing. E.g. : computing the
average of a set of readings in an array
Run to completion with respect to other tasks.Only
need a single stack.

The nesC Language


nesC – network embedded
systems C

Application
(nesC)
nesC
compiler

TinyOS kernel(C)
TinyOS libs(nesC)

Application &
TinyOS (C)
C
compiler

Application
executable

The nesC Language








An extension to the C programming language, to
embody the concepts and execution model
of TinyOS.
Filename extension .nc
Static language
 No dynamic memory(malloc)
 No function pointers
 No heap
Includes task FIFO scheduler.
Designed to encourage code reuse.

TinyOS

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