chapter 13 embedded systems patricia roy manatee community college, venice, fl ©2008, prentice hall...
TRANSCRIPT
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Chapter 13Embedded Systems
Patricia RoyManatee Community College, Venice,
FL©2008, Prentice Hall
Operating Systems:Internals and Design Principles, 6/E
William Stallings
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Embedded System
• Hardware and software designed to perform a dedicated function
• Tightly coupled to their environmnet
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Examples
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Examples
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Embedded System Organization
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Characteristics of Embedded Operating System
• Real-time operation• Reactive operation
– Respond to external events
• Configurability– Large variation in systems so need flexible
configuration
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Characteristics of Embedded Operating System
• I/O device flexibility• Streamlined protection mechanisms• Direct use of interrupts
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Adapting an Existing OS
• Add real-time capability• Streamlining operation• Add necessary functionality
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eCos
• Embedded Configurable Operating Systems
• Open source• Royalty-free• Real-time OS• Most widely used embedded OS
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eCos Configuration Tool
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eCos Configuration Tool
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Loading an eCos Configuration
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eCos Layered Structure
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Hardware Abstraction Layer
• Presents consistent API to upper layers• Different for each hardware platform
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HAL
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HAL Modules
• Architecture– Processor family type
• Variant– Support features of specific processor
• Platform– Support of tightly coupled peripherals
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eCos Kernel
• Low interrupt latency• Low task switching latency• Small memory footprint• Deterministic behavior
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Not in eCos Kernel
• Memory allocation• Device driver
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eCos I/O System
• Framework for supporting device drivers
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eCos Scheduler
• Bitmap scheduler– Efficient for small number of threads active– Each thread has different priority
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Bitmap Scheduler
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eCos Scheduler
• Multilevel queue scheduler– Appropriate when number of threads is
dynamic– Multiple threads at each priority– Time slicing
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Multilevel Queue Scheduler
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eCos Thread Synchronization
• Mutexes• Semaphores• Condition variables
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eCos Thread Synchronization
• Event flags• Mailboxes• Spinlocks
– Useful in SMP (symmetric multiprocessing)
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Mutexes
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Mutexes and Condition Variables
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Mutexes and Condition Variables
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TinyOS
• 400 bytes of code• Not a real-time OS• No kernel• No memory protection
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Tiny OS
• Component-based OS• No processes• No memory allocation• Interrupt and exception handling
dependent on peripheral• Nonblocking
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Wireless Sensor Network Topology
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TinyOS Goals
• Allow high concurrency• Operate with limited resources• Adapt to hardware evolution
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TinyOS Goals
• Support a wide range of applications• Support a diverse set of platforms• Be robust
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TinyOS Components
• Single-hop networking• Ad-hoc routing• Power management• Times• Nonvolatile storage control
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TimerM Component
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TimerM Configuration
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TinyOS Scheduler
• Operates across all components• Only one task executes at one time• Simple FIFO queue
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Example TinyOS Appliction
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Example TinyOS Appliction
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TinyOS Resource Interface
• Dedicated• Virtualized• Shared
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Shared Resource Configuration