Giotto

1. Giotto www.eecs.berkeley.edu/~fresco/giotto Embedded Control Systems Development with Thomas A. Henzinger Ben Horowitz Christoph M. Kirsch University of California, Berkeley (presented by Marius Minea)

2. Embedded Systems Development Application models derives simulates Control Engineer Control Design Matlab Functionality & Timing Giotto Program decomposes implements tests Software Engineer Distributed Platform Giotto!

3. Our Approach The Time-Triggered Paradigm [Kopetz]: -all communication activities triggered by clock -predictability (i.e., verifiability) -safety-critical applications (e.g., automotive) TTA: hardware & protocol realization Giotto: programming language realization

4. Motivating Example: Flight Control (DARPA SEC Program)

5. INU task pitch control aileron 1 task GPS task aileron 2 task air data task tailplane task throttle control pilot task rudder task thrust task Periodic Tasks roll control Sensor tasks Control tasks Actuator tasks

6. 200 Hz 1 kHz 200 Hz 1 kHz

7. Modes • Control system of airplane is designed to operate in different modes. In each mode a particular set of controllers is deployed. There are switches between modes. • For example: • Navigational modes (taxi, takeoff, cruise). • Maneuver modes (dive, roll). • Fault tolerance modes (track which hardware is working).

8. Giotto • Giotto is a tool-supported methodology for embedded control systems design • Giotto consists of • a time-triggered and platform-independent programming language • a compiler • a runtime library • Giotto provides an abstract programmer’s model

9. The Giotto Methodology Functionality & Timing Giotto Program Compilation Scheduling & Communication Giotto Executable Giotto Runtime Library RTOS, e.g., VxWorks Distributed Platform

10. Task Definition: Abstract Syntax State Input ports f Output ports Period

11. Task Invocation:Time-Deterministic Semantics Task State Input ports f Output ports Period 10ms Time Read @ time t Write @ time t+10ms

12. Task Invocation:Time-Deterministic Semantics Actual time the task uses the CPU (may be preempted) Task State Input ports f Output ports Period 10ms Don’t care Time Read @ time t Write @ time t+10ms

13. Input/Output:Sensors-Control Law-Actuators State Sensors f Actuators

14. Inter-task Communication: Connections P Q

15. Different Periods Task P Q Q Time t t t+5ms t+5ms t+10ms

16. Q-to-Q Connection P Q

17. Zero-Delay Semantics Task P Q Q Time t t

18. P-to-Q Connection P Q

19. Zero-Delay Semantics Task P Q Q Time t t

20. Time-Deterministic Semantics Task P Perhaps on same CPU Q Q Don’t care Time t t+5ms t+5ms

21. Time-Deterministic Semantics Task P Q Q Time t t+5ms t+5ms

22. Time-Deterministic Semantics Task P Most recent value guaranteed to be available (may have to be buffered) Q Q Time t t+5ms t+5ms

23. Time-Deterministic Semantics Task P Q Q t t+5ms t+5ms t+10ms t+10ms

24. An Abstract Programmer’s Model High-Level Programming Giotto Functionality Input/Output Ports Time-Determ. Computation Zero-Delay Communication Timing

25. Giotto Modes • Multi-modal control • Fault tolerance • Event modeling • Resource sharing • Uncertain environments Some Motivations:

26. Giotto Modes • A mode is a parameterized set of tasks. • A Giotto program consists of a set of modes and mode switches. • A Giotto system is in a single mode at any given time.

27. Abstract Syntax of a Mode Entry Port P 1 Q 2 Period 10ms Frequencies

28. Abstract Syntax of a Mode Switch Connection M M’ Frequency2: evaluation of trigger predicate every 5ms Trigger predicate

29. Mode M P 1 Connection Q 2 Period 10ms

30. Mode M’ P 1 R 4 Connection Period 10ms

31. Concrete Syntax startm ( ) { modem ( )period10 ms{ taskfreq1doP ( ) ; taskfreq2doQ ( x, y ) ; exitfreq2ify = 5thenm’ ( y ) ; } modem’ ( int z )period10 ms{ taskfreq1doP ( ) ; taskfreq4doR ( x, z ) ; } } Tasks are C procedures

32. Semantics of the Mode Switch Task P P Q Q R Easy Case: Mode Switch @ t+10ms t+10ms

33. Semantics of the Mode Switch Task P Q Time Interesting Case: Mode Switch @ t+5ms

34. Semantics of the Mode Switch Task P P Q R R R t+5ms t+5ms t+7.5ms t+10ms

35. Mode M P 1 Connection Q 2

36. Semantics of the Mode Switch Task P Mode switch already finished! Q R R Time t+5ms t+5ms

37. Mode M’ P 1 R 4 Connection

38. Semantics of the Mode Switch Task P Q R R Time t+5ms t+5ms

39. Mode M’ P 1 R 4 Connection

40. Semantics of the Mode Switch Task P Q R R Time t+5ms t+5ms

41. Mode M’ P 1 R 4 Connection

42. Semantics of the Mode Switch Task P Initial value Q R R Time t+5ms t+5ms

43. Semantics of the Mode Switch Task P Q R R Time

44. The Abstract Programmer’s Model High-Level Programming Giotto Functionality Input/Output Ports Time-Determ. Computation Zero-Delay Communication Timing Decomposition Modes

45. The Giotto Compiler • Automatic code generation • Compilation directives in the form of Giotto annotations for distributed platforms

46. The Giotto Compiler Giotto Program • Two possible answers: • Giotto executable • “Not schedulable” Giotto Compiler (either because program overconstrained, or because compiler not smart enough) Giotto Executable

47. Closing the Gap:Giotto-Architecture Annotations Giotto Program Hosts (CPUs), Nets, Worst-case execution / transmission times Giotto-A Program Giotto Compiler Distributed Platform

48. Closing the Gap:Giotto-Mapping Annotations Giotto Program Giotto-A Program Hosts, Nets, Performance Tasks to Hosts, Connections to Nets Giotto-AM Program Giotto Compiler Distributed Platform

49. Closing the Gap:Giotto-Schedule Annotations Giotto Program Giotto-A Program Hosts, Nets, Performance Tasks to Hosts, Connections to Nets Giotto-AM Program Tasks to Priorities (say), Connections to TDMA (say) Giotto-AMS Program Giotto Compiler Distributed Platform

50. Platform Dependency Computation Task P Q Q Time