1. Chapter 13 Embedded Systems Patricia Roy Manatee Community College, Venice, FL ©2008, Prentice Hall Operating Systems: Internals and Design Principles, 6/E William Stallings

2. Embedded System Hardware and software designed to perform a dedicated function Tightly coupled to their environmnet

3. Examples

5. Embedded System Organization

6. Characteristics of Embedded Operating System Real-time operation Reactive operation –Respond to external events Configurability –Large variation in systems so need flexible configuration

7. Characteristics of Embedded Operating System I/O device flexibility Streamlined protection mechanisms Direct use of interrupts

8. Adapting an Existing OS Add real-time capability Streamlining operation Add necessary functionality

9. eCos Embedded Configurable Operating Systems Open source Royalty-free Real-time OS Most widely used embedded OS

10. eCos Configuration Tool

12. Loading an eCos Configuration

13. eCos Layered Structure

14. Hardware Abstraction Layer Presents consistent API to upper layers Different for each hardware platform

15. HAL

16. HAL Modules Architecture –Processor family type Variant –Support features of specific processor Platform –Support of tightly coupled peripherals

17. eCos Kernel Low interrupt latency Low task switching latency Small memory footprint Deterministic behavior

18. Not in eCos Kernel Memory allocation Device driver

19. eCos I/O System Framework for supporting device drivers

20. eCos Scheduler Bitmap scheduler –Efficient for small number of threads active –Each thread has different priority

21. Bitmap Scheduler

22. eCos Scheduler Multilevel queue scheduler –Appropriate when number of threads is dynamic –Multiple threads at each priority –Time slicing

23. Multilevel Queue Scheduler

24. eCos Thread Synchronization Mutexes Semaphores Condition variables

25. eCos Thread Synchronization Event flags Mailboxes Spinlocks –Useful in SMP (symmetric multiprocessing)

26. Mutexes

27. Mutexes and Condition Variables

29. TinyOS 400 bytes of code Not a real-time OS No kernel No memory protection

30. Tiny OS Component-based OS No processes No memory allocation Interrupt and exception handling dependent on peripheral Nonblocking

31. Wireless Sensor Network Topology

32. TinyOS Goals Allow high concurrency Operate with limited resources Adapt to hardware evolution

33. TinyOS Goals Support a wide range of applications Support a diverse set of platforms Be robust

34. TinyOS Components Single-hop networking Ad-hoc routing Power management Times Nonvolatile storage control

35. TimerM Component

36. TimerM Configuration

37. TinyOS Scheduler Operates across all components Only one task executes at one time Simple FIFO queue

38. Example TinyOS Appliction

40. TinyOS Resource Interface Dedicated Virtualized Shared

41. Shared Resource Configuration