nesC 1'2

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nesC 1.2

• David Gay
• Intel Research Berkeley

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Introduction

• nesC 1.2 is a major revision to the nesC language
• external types (with Kevin Chang, UCLA)
• generic components
• binary components
• attributes
• Goals
• simplify TinyOS programming
• make it easier to define new abstractions and
  services

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External Types Why?

• Current message formats defined as C structures
• machine-dependent representation
• different padding
• different endianness
• Until recently, not a problem
• homogeneous networks, with platform-specific
  radios
• mig tool decodes structures for PCs
• Now 802.15.4 on telos, micaz, imote2
• want interoperability!

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Standard Solutions

• Marshalling/unmarshalling
• needs extra RAM
• protocol stack built by wiring components, so no
  obvious central place to do marshalling/unmarshall
  ing
• Unix-style htons, htonl, etc calls
• programmer-unfriendly
• only addresses endiannness
• gccs packed attribute
• only addresses padding

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External Types

• nesC 1.2 introduces external types, which have
  a platform-independent representation
• OLD NEW
• struct TOSMsg nx_struct TOSMsg
• uint16_t addr nx_uint16_t addr
• uint8_t group nx_uint8_t group
• nx_structs have no padding
• nx_uint16_t, etc are big-endian on all platforms
• these types can be used like any C types (some
  minor restrictions)
• Very easy to convert TinyOS code to use external
  types

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Generic Components

• Components with numeric and type arguments, that
  can be instantiated at compile-time
• Interfaces can also have type arguments
• Uses
• utility components filters, adapters, queues,
  buffers, etc
• wiring patterns see OSKI

generic module QueueC(typedef t, int n)
provides interface Queuelttgt implementation
t qn
configuration App implementation
components AppM, new QueueC(TOSMsg, 10) as
MyQ AppM.MsgQ -gt MyQ
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Other Changes (in brief)

• Attributes (inspired by Java 1.5)
• programmers can add custom annotations to nesC
  programs
• external tools can extract program information
• uses wiring checks, network management
  attributes, etc
• Binary components
• compile nesC app to .o file with specified
  entry, exit points
• uses
• build, use, distribute components in binary form
• encapsulate set of components as C library

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Status

• All features implemented
• Alpha release at http//sf.net/projects/nescc
• Being used for TinyOS 2.x development work
• Will be released with TinyOS 2.0

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Backup
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Generic Configurations

• generic configuration SomeAssembly()
• provides interface X
• implementation
• components new SomeAssemblyM() as SA,
• new QueueC(TOSMsg, 10) as SomeQ
• X SA.X
• SA.Queue -gt SomeQ
• Every instantiation of SomeAssembly will create
  new instances of SomeAssemblyM and IntQueueC

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Generic Interfaces

• Many interfaces similar, except for result,
  argument types
• Generic interfaces support this by allowing
  interfaces to take type parameters
• Two generic interfaces are connectable iff they
  have the same type arguments
• Generic components with type arguments can use
  generic interfaces to
• Provide functionality dependent on that type
• Express requirements of operations on that type

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configuration MyApp implementation
components MyCode, new QueueC(int, 10) as
MyQ MyCode.Queue -gt MyQ

• interface Queuelttgt
• command void push(t x)
• command t pop()
• generic module QueueC
• (typedef t, int n)
• provides interface Queuelttgt as Q
• implementation
• t qn
• int p1, p2
• command void Q.push(t x)
• qp1 x
• if (p1 n) p1 0

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Another example

• interface Comparelttgt
• command bool lessthan(t x1, t x2)
• generic module Sort(typedef t)
• uses interface Comparelttgt as C
• implementation
• void f()
• t x1, x2
• if (call C.lessthan(x1, x2))

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Binary Components

• component ExternalInterface
• provides interface StdControl
• uses interface Timer
• entry points (of program including
  ExternalInterface)
• ExternalInterface.Timer.fired
• exit points
• ExternalInterface.StdControl.init, start, stop
• ExternalInterface.Timer.start, stop

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Attributes

• struct _at_atmostonce
• struct _at_snms int key
• provides interface Timer _at_atmostonce()
• provides interface SNMSAttribute
  _at_snms(KEY_PARENT)
• Information on attributes, etc output in XML
• Java-based parser for this XML schema
• Sample wiring check demo app