Advanced Embedded Systems Design

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Advanced Embedded Systems Design

• BAE 5030 - 003
• Fall 2004
• Instructor Marvin Stone
• Biosystems and Agricultural Engineering
• Oklahoma State University

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Overview Of Embedded Systems Design

• Embedded systems
• Definition The special function micro-controller
  based element integrated into an engineered
  system
• Provide control and user interface functions
• May or may not be real-time
• Real-time Provides that quality of processing
  events as they happen and collecting information
  as it is available and providing control outputs
  and necessary responses within specified time
  constraints.
• What is not an embedded system
• General purpose microcomputer
• Non micro-controller based electronic components
  of a system
• Embedded systems design
• Requirements specification, planning,
  development, and specification for manufacture of
  the hardware and software for embedded systems.

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Goals of BAE 5030-003 Embedded systems design

• To provide an introduction to methods and
  techniques for planning embedded systems
• To provide an introduction to task scheduling and
  development of time-triggered embedded systems
• To provide an introduction to event scheduled
  embedded systems
• To focus primarily on software at the system
  design and development level. Hardware will be
  covered with regard to interfacing basics and
  system level aspects, but other courses address
  electronic hardware design
• To develop hands-on competency in development of
  multi-tasking embedded software

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Web-site for BAE 5030

• Course materials website
• http//biosystems.okstate.edu/home/mstone/5030_04/
  5030_04index.htm
• Includes syllabus, downloads, lectures resources,
  assignments
• Course syllabus
• http//biosystems.okstate.edu/home/mstone/5030_04/
  outline/bae5030_sched.htm

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Topical review

• Embedded systems operating environments
• Event and time triggered tasking
• main()ISR, RTOS, and quantum approaches
• Cooperative, pre-emptive, time triggered and
  shared clock scheduling
• Rate Monotonic Analysis
• Planning and design of embedded systems
• Use of state machine and statechart descriptions
• Inter-task communication and task synchronization
• Application of a Quantum framework paradigm
• Management of communications
• Asynchronous queuing strategies
• Asynchronous serial/SPI/I2C
• Network communications
• Multi-processor strategies
• Implementation of control systems
• Monotonicity
• Control interfacing
• Distributed systems techniques
• Requirements specification for embedded systems

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Course style

• 15 3-hour class meetings
• Questions on reading
• 1 hour lecture from instructor
• 0.5 hour problem review or reading assignment
  review from student
• Demonstration from instructor
• Final exam
• Pre-requisites
• Completion of an undergraduate class in automatic
  control design
• Completion of an undergraduate level class in
  embedded systems
• Completion of an undergraduate class in
  electronics hardware

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Introduction to an Embedded Systems Design Process

• System planning process
• Develop thorough requirements specification
• Set a realistic project schedule
• Identify the significant tasks that will be
  needed to produce the ES
• Identify the resources available to conduct the
  development
• System designer
• Programmers
• Hardware designers
• Testers
• Budget and accounting
• Project management
• Documentors
• Explainors
• Assign resources, time and schedule to tasks
• Include reasonable contingency
• Make an initial hardware selection
• Develop a software plan
• Context diagram
• Data flow diagram

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Introduction to an Embedded Systems Design Process

• System preliminary design
• Develop an initial hardware design
• Review the hardware and software plans to assure
  requirements will be met
• Obtain hardware prototypes for software
  development
• Develop the software
• Develop and test driver level software on the
  prototypes
• Must include basic test software
• Develop the first draft of the application level
  software
• Develop the hardware design to the schematic
  level
• Review the hardware and software designs to
  assure they meet the requirements specification
  Adjust as appropriate
• Create first draft system hardware and software
  documentation
• System final design
• Revise the software to second draft
• Revise the hardware schematic
• Build and assemble hardware

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Introduction to an Embedded Systems Design Process

• System test
• Receive and test the target hardware with the
  previously developed drivers and test software
• Revise prototype hardware as necessary
• Install and test second draft software
• System final design
• Create final hardware schematics
• Create third draft final software design
• Fabricate final hardware prototype(s)
• Install and test final software and hardware
• Revise system documentation
• Deliver system

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Goals for Class Today

• Introduce course (done)
• Embedded Systems (done)
• Introduce graphical system planning tools
• Context diagrams
• Data flow diagrams
• Statecharts as a tool for specifying event driven
  systems
• Introduce Keil Compiler
• Set assignments

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Behavioral Modeling

• Logic tables a tabular relationship between all
  inputs and outputs. Inputs and outputs can
  include parameters in memory
• Statecharts modeling technique suited to
  describing systems where past state or memory
  defines the transitions to the next state
• Mealy automata processes occur on transitions
  between states
• Moore automata processes occur within a state
• UML - Unified Modeling Language specifies a
  syntax for state machine modeling

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Statechart definitions

• State - a distinguishable consistent
  characteristic behavior of a system that persists
  for a significant period of time
• Event a change in stimulus to a system that
  occurs in an infinitesimal period of time
• Transitions - responses to events that move the
  system from state to state
• Finite State Machine A model of a system and
  its behavior that captures states, events, and
  transitions between states
• Finite State Machine characteristics
• Characteristic behavior within a state is
  distinct and unchanging
• Finite number of states
• Residence time in states is a significant period
• Transitions are the response of the system to
  events
• Transitions between states are distinct and
  unchanging
• Transitions between states are finite in number
• Transition time between states is infinitesimal

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Statechart elements and syntax

• Start occurs at the initial pseudo state
• The trigger event causes the change of state if
  the guard condition is true
• System may exit the top state when the final
  state is reached
• Time between states is infinitesimal
• Elements (Simple statecharts)
• Initial state
• State
• Transition
• Event
• Trigger
• Guard
• Action
• Final state

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Statechart Example
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Hierarchical State Example
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Modified statechart for Lowering mode

• Handle case where current is high when
  determining mode
• Explicitly handle testing for time in
  determining lowering mode

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Software structure to realize a state machine

• Many possibilities but typical isinfinite loop
  encompassinga case structure. (see Samek)
• Consider the following example

void Process_State_0( void ) state STATE_1
while((!Trigger_5) (state STATE_3))
switch (state)      case STATE_1         
if (Trigger_1) process_1()
state STATE_2
        break     case STATE_2          if
(Trigger_2) process_2()
state STATE_2
if (Trigger_3) process_3()
state STATE_2   
      break      case STATE_3 if
(Trigger_4) process_4()
state STATE_1
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Concurrent tasks
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Context diagrams

• Usage
• Define the extents of a system
• Define elements of a system
• Define information flow from external elements to
  or from the system
• Process for construction
• Identify external elements that communicate with
  the system
• Identify data that are the object of the
  communications
• Construct the diagram that connects the external
  elements to the system with lines representing
  the communication

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Example Context Diagram
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Dataflow Diagram

• Usage
• Define the movement of information to, from, and
  within a system
• Define processing elements and data stores of a
  system
• Define information (data) flow to and from
  processing elements of a system
• Process for construction
• Identify processing elements of the system
• Identify data passed to, from and between
  processes in the system
• Construct the diagram that connects the data
  flows to processing elements of the system

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Example dataflow diagram
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Assignment

• Code the door control example in C
• Read Pont, Chapters 1,2,3,6 (Review 4,5,7,8 as
  necessary)
• Read Samek, Chapter 1,2,3
• Tutorial 30 min
• Explain how an interrupt and return from
  interrupt works at the machine level on an 8051.
  Explain the situation where an interrupt has
  occurred and then another occurs.