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Design and realization of experiments for an embedded Linux Laboratory class

Design and realization of experiments for an embedded Linux Laboratory class. Ciaran mc Girl 4 th Electronic and Computer Engineering Project Presentation April 2008. Topics:. Brief Project Overview Real Time Systems RTAI Experiments Documented Problems Encountered Future development

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Design and realization of experiments for an embedded Linux Laboratory class

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  1. Design and realization of experiments for an embedded Linux Laboratory class Ciaran mc Girl 4th Electronic and Computer Engineering Project Presentation April 2008

  2. Topics: • Brief Project Overview • Real Time Systems • RTAI • Experiments Documented • Problems Encountered • Future development • Questions

  3. Brief Project Overview: -Set up a workingset of real-time laboratory exercises,togetherwith proper documentation, a supportingsoftware infrastructure andsome Guidelinesfor laboratory supervisors. -Experiments vary from running a single task program to a task with a variable period.

  4. Real-time Systems A real time system is where its application is considered to be mission critical, with a set deadline in which to be completed, if the application misses it’s deadline then it’s said to have failed Hard Real-time Systems Soft Real-time Systems

  5. RTAI – Real Time Application Interface RTAI is not a real time operating system but instead takes priority over Linux at low level and in doing so leaves Linux as a low priority task so it cannot interrupt the RTAI.

  6. RTAI - How It works: Consists basically of an interrupt dispatcher, mainly traps the peripherals interrupts and if necessary re-routes them to Linux; using the concept of HAL (Hardware Abstraction Layer) kernel kernel RTAI Hardware Hardware

  7. RTAI Installation • Download a new kernel and the RTAI • Patching this kernel with the RTAI • Compile and install the kernel • Documented for student installation

  8. Experiments Documented • Single Periodic Task • Periodic scheduling of two tasks • Variable Period Task

  9. Single Periodic Task • Single Task using a set period • Toggles the PC speaker, emits a tone using Pulse width modulation

  10. Single Periodic Task Contd. • Laboratory Session Developed • Initialise a task • Name a task • Remove a module

  11. Periodic Scheduling of Two Tasks • Two tasks that run at two different periods • One task toggles the PC speaker every 100ms like the first experiment with the addition of having to decrement a variable before each toggle. • The other task runs every second and increments the variable used by the first task. • This increases the time between toggles and causes the tone to lower.

  12. Periodic Scheduling of Two Tasks Contd. Laboratory Session Developed • Working with the original experiment, develop another task to increase the delay between the toggles (using a shared variable)

  13. Variable period Task • Uses One-Shot mode • Task runs until completion • A delay is incremented and decremented and so the tone from the PC speaker is increased and decreased repeatedly.

  14. Variable period Task contd. Laboratory session developed • Introduce the students to one shot mode and how the task operates. • The students must then incorporate the delay for the task to sleep.

  15. RTAI-Lab • XRTAILAB - GUI Included with the installation of RTAI • Scilab (open source MATLAB Equivalent) with a Scicos extension. • Then RTAI-Lib extension is added to Scicos • Various other Installations including Mesa

  16. RTAI-Lab contd. Sine Wave example

  17. Problems Encountered • 64 bit Architecture • AMD Processor • Ubuntu Distribution of Linux • Mesa library problems

  18. Future Development • More Documented Experiments • Remove any “teething” problems with current documented ones. • The RTAI-Lab could be used to help students with the understanding of real-time programming with the visual aid of the blocks in the system.

  19. Questions?

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