How to Code on TinyOS Xufei Mao Advisor: Dr. Xiang-yang Li CS Dept. IIT

Outlines What is TinyOS? What is TinyOS? Hardware & Software Hardware & Software NesC NesC A simple example A simple example Conclusion Conclusion

So why do we need a new OS?

Traditional OS   Huge !   Multi-threaded architecture =>large memory   I/O model   Kernel and user space separation   Typically no energy constraints   Ample available resources

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

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

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

The Hardware

Software TinyOS (Platform) TinyOS (Platform) Coding language Coding language  NesC (Network Embedded System C)

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

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

Components Two type of components Two type of components  Module  component written with code  Configuration  components wired together

Components

TinyOS Application (Sample)

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

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

nesC Keywords

nesC Keywords -implementation

Interfaces

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

Modules (Sample)

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 -> endpoint2   endpoint1 endpoint1)

Configurations (Sample)

nesC Wiring Syntax

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.)

Simple Example 1 Blink Application Blink Application  Blink.nc configuration

Simple Example 1 Blink Application Blink Application  BlinkM.nc module

Simple Example 2 Communication between two sensors Communication between two sensors Environment : Xubuntu + TinyOS 2.0 Environment : Xubuntu + TinyOS 2.0 Hardware: TelosB sensors Hardware: TelosB sensors

Resources Gaurav’s TinyOS-1.x installation howto:   tup.htm Tinyos-2.x installation howto (straightforward):   tinyos.html The official TinyOS tutorial (pretty good):   The offical TinyOS-2.x tutorial (very good):   2.x/doc/html/tutorial/index.html nesC:

Resources Other Docs:   nesC paper: /nesc-pldi-2003.pdf   nesC manual: /nesc-ref.pdf   TinyOS abstractions: /tinyosnsdi04.pdf

Reference TinyOS Tutorial by TinyOS Tutorial by Jeremy Gummeson, Sensors Lab, UMass-Amherst TinyOS Programming by Philip Levis nesC paper: sc-pldi-2003.pdf

Conclusion