Embedded Operating Systems

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Embedded Operating Systems

• By
• Daniel Gomez, Zhenghui Cai
• Johns Hopkins University
• Montgomery Campus
• Foundations of Software Engineering
• 605.400.71
• Fall 2003
• Dr. Yan Yufik

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What do these devices have in common?
Embedded Linux Operating System
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The Operating System(A Modular Abstraction)

• Software Layers
• Embedded OS
• Simple Function
• Size
• Hardware
• Cost

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Real-Time Operating System(RTOS)

• Deadlines
• A soft real-time system can tolerate latency when
  missing the ideal deadline.
• A hard real-time systems are best described as
  those when it absolutely positively has to be
  done on time or the system crashes.

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Thread vs. Process
http//www.lynuxworks.com/products/posix/processes
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Thread vs. Process
http//www.lynuxworks.com/products/posix/processes
.php3
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Thread vs. Process
http//www.lynuxworks.com/products/posix/processes
.php3
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Scheduling Policy

• Cooperative
• Round-Robin
• Priority Based

http//www.lynuxworks.com/products/posix/processes
.php3
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Priority Inversion
Selecting the Right RTOS - A Comparative Study,
March 2002
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COMPARISONS
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Embedded Linux (1)

• Pros
• Rich Supported Hardware
• Security and Reliability
• Rich Software Library Support
• Diversified Tools

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Embedded Linux (2)

• Cons
• Open Source
• Size
• Development Tools
• Real Time
• Management

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Embedded Linux (3)

• Suitable Applications
• Relatively Small Non-time Sensitive Applications
• New Development
• Real Time Feature
• Compliant Kernel
• Dual Kernel
• Core Kernel

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Windows CE (1)

• Pros
• Rich Multimedia Features
• Mature Management And Long Time Development
• Rich Library
• Good Support
• Excellent Development Tools
• Hard Real Time Feature

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Windows CE (2)
Hard Real Time feature in Embedded Windows
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Windows CE (3)

• Cons
• Closed Source
• Hardware Support is limited
• Not been tested widely
• Royalty Fee
• At Least 3 Per Unit

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Windows CE (4)

• Suitable Applications
• Large Application
• Multimedia Requirement
• New Development
• Multimedia Support
• Memory Management
• Size
• Security protocol Support

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vxWorks (1)

• Pros
• Small Foot Print
• Protection Domains
• Wide Processor Support
• Good IDE Support (Tonado)
• Advanced Loader

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vxWorks (2)

• Cons
• Poor Graphic Interface
• Poor Multimedia Support
• Closed Source
• Suitable Applications
• Defense System
• Automotive System
• Telecommunication System

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Cross Comparison
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FUTURE TRENDS
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Market Trends
Data source Embedded Systems Developer Survey,
Volume 2, 2002 OSes targeted in current and next
embedded projects
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Open Source

• Share-Cropping vs. Ownership
• Open Platform ? Open Source
• Challenges Ahead

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Is Linux Ready for the Future?

• Kernel 2.6
• On-Time Arrival Deterministic
• No Delays Preemtible
• Just Say No No Keyboard, No Monitor, No Wires

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Most Common Mistakes with RTOS Software
Development

• Delays implemented as an empty loop
• Software engineers not participating in hardware
  design
• Generalizations based on a single
• architecture
• No memory analysis
• Improper use of Global variables
• Indiscriminate use of interrupts
• One Big Loop
• Too many inter-module and circular dependencies
• No measurements of execution time

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Future development and Prediction

• Expert system applied in IDE to minimize common
  mistakes
• Desktop system will be replaced by embedded
  system
• Desktop full-featured operating system will be
  replaced by/ merged with embedded operating
  system.
• The Future is Open Source

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MERRY CHRISTMAS!!!