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Q uantitative E valuation of E mbedded S ystems

Q uantitative E valuation of E mbedded S ystems. Q uantitative E valuation of E mbedded S ystems. TDMA in a cyber physical system: preparation for the SDF3 assignment. Sharing Resources. No sharing – dedicated resources. Alternating access, round robin. Fixed priority.

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Q uantitative E valuation of E mbedded S ystems

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  1. Quantitative Evaluation of Embedded Systems

  2. Quantitative Evaluation of Embedded Systems TDMA in a cyber physical system: preparation for the SDF3 assignment

  3. Sharing Resources

  4. No sharing – dedicated resources

  5. Alternating access, round robin

  6. Fixed priority

  7. First-come first serve ?

  8. Time Division Multiplexing (1) Slice = S Period = P TP/S P-S Task = T

  9. Time Division Multiplexing (2) NEW!! Publication under submission... RTAS 2014 r r Slice = S Period = P 0 S/q P-S q P-(S/q) Task = T qT = rS

  10. A cyber physical system Sensor 1 Temperature Actor 1 Valve Comp. Inner control Sensor 2 Pressure Actor 2 Motor xyz Comp. Emergency detection Sensor 3 Camera Actor 3 Motor rot. Comp. Image processing Sensor 4 Microphone Physical World

  11. Dataflow of the control cycle Comp.1 Inner control Sensor 1 Temperature Actor 1 Valve Sensor 2 Pressure Actor 2 Motor xyz Comp.2 Emergency detection Sensor 3 Camera Actor 3 Motor rot. Comp.3 Image processing Sensor 4 Microphone

  12. Packet-flow of the control cycle p1 Comp.1 Inner control p16 Sensor 1 Temperature p5 p9 Actor 1 Valve p6 Sensor 2 Pressure p10 p11 p17 Actor 2 Motor xyz p2 Comp.2 Emergency detection p12 Sensor 3 Camera p3 p13 p7 p15 Actor 3 Motor rot. Comp.3 Image processing Sensor 4 Microphone p4 p14 p18 p8

  13. Network topology Actor 2 Motor xyz Sensor 1 Temperature Comp. Inner control Comp. Emergency detection Sensor 3 Camera Sensor 4 Microphone Sensor 2 Pressure Comp. Image processing Actor 1 Valve Actor 3 Motor rot.

  14. Network topology Actor 2 Motor xyz Sensor 1 Temperature Comp. Inner control Comp. Emergency detection Sensor 3 Camera Sensor 4 Microphone Sensor 2 Pressure Comp. Image processing Actor 1 Valve Actor 3 Motor rot.

  15. Packet flow + Network hops Comp.1 Inner control Sensor 1 Temperature Actor 1 Valve Sensor 2 Pressure Actor 2 Motor xyz Comp.2 Emergency detection Sensor 3 Camera Actor 3 Motor rot. Comp.3 Image processing Sensor 4 Microphone

  16. Packet flow + Network hops + Processor sharing Sensor 1 Temperature Actor 1 Valve Sensor 2 Pressure Actor 2 Motor xyz Sensor 3 Camera Actor 3 Motor rot. Sensor 4 Microphone

  17. Packet flow + Network hops + Processor sharing + Sampling times Actor 1 Valve Actor 2 Motor xyz Actor 3 Motor rot.

  18. Packets + Network + Processor + Sampling + Feedback Latency 1 L2 L3

  19. Time Division Multiplexing (2) r r Slice = S Period = P 0 S/q P-S q P-(S/q) Task = T qT = rS

  20. Filling in the details: Network sharing • One packet per slice in the network, therefore T = S = 0.01 ms • One slice per node in the network • But... each node schedules its routing in a TDMA fashion as well...So for each hop P = (C+1)*N*S where C is the number of connections and N is the total number of nodes in the network. Slice = S Period = P Task = T qT = rS

  21. Filling in the details: Proc. sharing • Three computations = three slices, so P = S1 + S2 + S3 • Task times may be bigger than slice times! • T1 = 0.5 ms • T2 = 3 ms • T3 = 7 ms • It is part of the assignment to figureout how P should be chosen anddivided over S1,S2 and S3. Slice = S Period = P Task = T qT = rS

  22. Filling in the details: The rates • Sensor 1 and 2 produce 1 packet every 2 ms • Sensor 3 produces 50 packets every 100 ms • Sensor 4 produces 10 packets every 20 ms • Computation 1 needs 1 packet from sensor 1 and 2, and produces 1 packet for computation 2 and one for actor 1 • Computation 2 takes 50 packets from computation 1 and 1 packet fromcomputation 3 and produces 1 for actors 2 and 3 and for computation 3. • Computation 3 takes 50 packets from sensor 3, 50 from sensor 4 and 1 packet from compation 2 and produces 1 for computation 2.

  23. The dataflow graph I prepared for you: hop1 hop2 hop9 1 hop10 hop11 hop12 Actuator1 2 ms Sensor1 Sensor2 Sensor3 Sensor4 Comp1 2 50 hop5 1 hop4 2 ms Actuator2 hop3 2 hop6 50 Comp2 50 hop13 2 100 ms 2 2 50 Comp3 Actuator3 10 hop14 20 ms hop15 hop8 hop7

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