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Introduction to role of embedded systems in society

Introduction to role of embedded systems in society

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Embedded Intro India05 Embedded Intro India05 Presentation Transcript

  • Embedded Computing Systems Rajesh Gupta, UC San Diego, CA mesl . ucsd . edu
  • Outline: what are embedded systems and what is so interesting about them?
    • What are embedded systems?
    • Embedded system characteristics
    • Challenges in Embedded Systems research and education
  • "Embedded Everywhere"
    • Generally, part of a larger system that may not be a “computer”
    • works in a reactive , time- and energy-constrained environment.
    • employs a combination of hardware & software (a “computational engine”) to perform a specific function;
      • Software is used for providing features and flexibility
      • Hardware = {Processors, ASICs, Memory,...} is used for performance (& sometimes security)
    An Embedded Computing System Application Specific Gates Processor Cores Analog I/O Memory DSP Code
  • Example: Automotive Embedded Systems Dominated by software and networking complexities
  • Control, processing, networking, …
    • Embedded, reactive controllers, for
      • Central locking system
      • Crash management
      • Power windows & seats
      • Airbag controller
      • etc.
    90 % of all innovations are SW-driven
    • Embedded processing for
      • Multimedia system
      • Navigation system
    • Infotainment alone uses up to 20 processors
  • Challenges in automotive embedded software
    • Highly complex , networked , and distributed
    • Consider processing
      • 70-80 electronic control units (ECUs) supporting hundreds of features
      • ECUs delivered by multiple suppliers, with their own software chains
    • Consider networking
      • Separate, integrated networks for power train, chassis, security, MMI, multimedia, body/comfort functions
      • Increasing interaction beyond car’s boundaries with devices, networks
    • Software development challenges:
      • hardware independence, information interdependence among subsystems, system composition, validation.
  • But that is just the beginning… Embedded Systems come in many (more) shapes.
  • Intel Montecito
    • Two 2-threaded 64b EPIC cores
      • Two threads hide memory latency on a single thread (TMT)
    • Total of 26.5 MB caches
    • 1.72 Billion transistors, 596 mm 2 , 90nm
  • 130 W; GBps
    • Generated clock frequency is a function of the measured voltage
      • -- 3X gain in power consumption
    MicroController 16 bit Instr 32 bit datapath 4K*16bit program 4K*8bit data 1 GHz, 5-stage pipe Real-time scheduler Power control Temperature control Calibration
  • Computers + Radios = Mobile Platforms
  • Sensor Nodes as Wireless Networked Embedded Systems Source: Estrin, MOBICOM’03
  • Indeed, computing nodes are changing rapidly
    • New computing nodes and networks are no longer monolithic entities
      • High-end processing migrating to mobile computing, sensor computing
      • Very likely sources of innovations in future for mainstream computing.
    Pointer to major sensor node platforms at http://mesl.ucsd.edu/gupta/SPOTSurl.html
  • Outline: what are embedded systems and what is so interesting about them?
    • What are embedded systems?
    • Embedded system characteristics
    • Challenges in Embedded Systems research and education
    • Application Specific
      • Perform a single or tightly knit set of functions;
      • (not usually "general purpose”)
    • Constrained
      • Power, cost and reliability are often important attributes that influence design;
    • Application specific processor design can be a significant component of some embedded systems.
      • Customization yields lower area, power, cost, ...
      • Higher HW/software development overhead
          • design, compilers, debuggers, ...
    Typical Characteristics
  • Real-Time Requirements
    • Hard-real time systems: where there is a high penalty for missing a deadline
      • e.g., control systems for aircraft/space probes/nuclear reactors; refresh rates for video, or DRAM.
    • Soft real-time systems: where there is a steadily increasing penalty if a deadline is missed.
        • e.g., laser printer: rated by pages-per-minute, but can take differing times to print a page (depending on the "complexity" of the page) without harming the machine or the customer.
      • However, the rate at which the image is delivered to the drum is a hard deadline, since the image will be lost otherwise.
    • Many systems have hard-deadlines imposed by the operations of peripherals, e.g., DRAM (refresh rate), disk (spin rate), cameras (scan rate), displays (refresh rate).
    • Modelling
      • the system to be designed, and experimenting with algorithms involved;
    • Refining (or “partitioning”)
      • the function to be implemented into smaller, interacting pieces;
    • HW-SW partitioning: Allocating
      • elements in the refined model to either (1) HW units, or (2) SW running on custom hardware or a general microprocessor.
    • Scheduling
      • the times at which the functions are executed. This is important when several modules in the partition share a single hardware unit.
    • Mapping (Implementing)
      • a functional description into (1) software that runs on a processor or (2) a collection of custom, semi-custom, or commodity HW.
    ES Design: Task Ingredients Environ -ment Processor Analog I/O Memory ASIC DSP Code
  • Scope and Ingredients of ES Design Tasks
    • The specific issues that need to be addressed in ES design depend to some extent on
      • the scope of the application at hand, and
      • the richness of the system delivered
    Dedicated system Digital Signal Processors General purpose processors Single Task General Task Mix Correlated Task Mix System + Application SW + SW environment Single Chip System + Applications Engine Control DFT
  • Programming with Time
    • E. G., Computing at the intersection of two different time topologies
    /* monitor temperature */ do forever { measure temp; if (temp < setting) start furnace; else if (temp > setting + delta) stop furnace; } /* monitor time of day */ do forever { measure time; if (6:00am) setting = 72; else if (11:00pm) setting = 60; } /* monitor keypad */ do forever { check keypad; if (raise temp) setting++; else if (lower temp) setting--; } Computing system Environment Sense Actuate
  • Programming with Location
    • Enabled by technology advances
      • Outdoor, indoor, absolute, relative, assertive
    • Infrastructure for location
      • Dynamic resource discovery and binding
      • Transparent location updates
      • Monitor resources in their environment
      • Virtual resource naming, that is, resources referred to based on their expected location
      • Reactive to changes in the resource availability
      • Control resource usage: access timeouts.
    • Programming with location
      • Spatial programming: how to use the location information in spatial references
  • One is already seeing time in programming
    • Absolute and relative delays
      • Delays as uninterruptible actions
      • Timeouts, timed procedure calls, wait selects
  • Of course, we have seen time before…
    • A process controller with following modules
      • a clock tick comes every 20 ms when a clock module must run
      • a control module must run every 40 ms
      • three modules with soft constraints
          • operator display update; operator input; information logs
    • Can be done synchronously (in one program) or asychronously through multiple tasks.
      • while (1) {
        • wait for clock; do clock module;
        • if (time for control) do control;
        • else if (time for display update) do display;
        • else if (time for operator input) do operator input;
        • else if (time for mgmnt. request) do mgmnt. output;
        • }
    • Must have t1 + max(t2, t3, t4, t5)  20 ms
        • may require splitting tasks… gets complex!
  • Multi-tasking
    • Most tasks are event driven
    • Asynchronous implementation approaches
      • Foreground/background systems : 2 tasks
      • Foreground (interrupt)
          • on interrupt {
          • do clock module; if (time for control) do control;
          • }
      • Background
          • while (1) {
          • if (time for display update) do display;
          • else if (time for operator input) do operator;
          • else if (time for mgmnt. request) do mgmnt.;
          • }
      • Decoupling relaxes constraint: t1 + t2  20 ms
    • Multi-tasking: also called processes, threads
      • Requires task scheduling, communication, sharing among tasks.
  • So, then how to organize multiple tasks?
    • Cyclic executive (Static table driven scheduling)
      • static schedulability analysis
      • resulting schedule or table used at run time
      • TDMA-like scheduling
    • Event-driven non-preemptive
      • tasks are represented by functions that are handlers for events
      • next event processed after function for previous event finishes
    • Static and dynamic priority preemptive scheduling
      • static schedulability analysis
      • no explicit schedule constructed: at run time tasks are executed “highest priority first”
      • Rate monotonic, deadline monotonic, earliest deadline first, least slack
  • Continued…
    • Dynamic planning-based scheduling
      • Schedulability checked at run time for a dynamically arriving task
      • “ admission control”
      • resulting schedule to decide when to execute
    • Dynamic best-effort scheduling
      • no schedulability checking is done
      • system tries its best to meet deadlines
    • Extensive literature on best scheduling methods with increasing complexity of tasks and architectures.
      • (Real-Time Symposiums).
    • This research has had an impact on how OS’s are structured for embedded systems…
  • OS Classes
    • General Purpose
      • Open, multiple applications, memory protection, multiple units of failure
      • Temporally unpredictable, large overheads
    • Real Time OS
      • Closed, single application, no memory protection, single unit of failure, temporally predictable, small system overhead
    • Consumer Electronics OS are in between
      • (CE Linux): Open, multiple apps, memory protection, temporally predictable, small overhead
  • Major OS Structures monolithic microkernel cyclic executive exo kernel
  • Outline: what are embedded systems and what is so interesting about them?
    • What are embedded systems?
    • Embedded system characteristics
    • Challenges in Embedded Systems research and education
  • A changing ecosystem of embedded systems “ Text” Timing- Dependent Data Real-World Sensor Inputs Single- or Few- Threaded Multi-Threaded OS Kernels/ Device Drivers MS Word cat Robotics Sensor Networks Distributed, Timing Dependent System MPI/Linda Distributed Robotics Squid TCP System/Internal Uncertainty Data/External Uncertainty Jeremy Elson, Microsoft
  • In the Human Body Source: Shkel (MAE), Ikei (Biomed), Zheng (ENT), UC Irvine
  • Into Fabrics and Buildings Ember radios and networks Source: Ember Networks
  • Summary: New “Computers”, New Challenges
    • Software development is a challenge with evolving processors
      • How to efficiently model, compile, target applications?
    • What is the right programming model for these systems?
      • What is the right set of OS, middleware services and API to provide a “usable” programming model?
    • Application modeling, programming for highly distributed, mobile, networked embedded systems
    • What happens in hardware versus software?
    • What is compiled and what happens dynamically?
    • What is done at the node, at the network?
    • How is awareness exploited?
      • Location, Energy, Connectivity
    • Getting it right means many more systems capabilities through software
      • Controlling power/energy usage, functional adaptivity, reliability, re/usability, availability, …
  • An emerging area for technical education
    • The design of embedded systems draws upon several disparate disciplines in CS and EE.
    • Application domain (Signal processing, ...)
    • Software engineering (Programming Languages, Compilers)
      • For implementing the software components; this can be a major component of several systems.
    • VLSI (computer aided) design
      • For implementing the custom and semi-custom hardware components.
    • Parallel/Distributed system design
      • since many embedded systems and multiprocessors are structured as a network of communicating processors; the network may be loosely coupled or tightly coupled.
    • Real-time systems (Hard- & soft- real time systems)
  • Cal-IT2  Systems Initiative
    • Part of the Cal-IT2 Core activities
    • SOC HyperIntegration Laboratory
      • Equipment and support for building board-level prototypes: key CalIT2 artificats such as CalRadio
      • Interfaces with ASIC design, test
    • Personnel supporting CalIT2 initiatives, visitors
      • Our interfaces with industry projects
      • Engineering personnel building prototypes, demonstration activities
      • Cal-IT2 students
    • Host projects, training and outreach
      • CalRadio, Damage Prognosis, MicroFluidic Sensing
  • Damage Prognosis in SHM
    • Supported through UCSD/LANL Engineering Institute
    • Goal: Monitoring Technologies for Large Scale Structures through sensing, computational modeling and predictive analysis
    • Field prototypes
      • Instrument large scale structures for continuous monitoring of structural health.
    Dasgupta, Gupta, Rosing, CSE, Michael Todd, MAE and Chuck Farrar, LANL