Slide 1: General Introduction to Embedded Systems

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Slide 1 General Introduction to Embedded Systems

• By
• Dr. Mouaaz Nahas
• Embedded Systems
• 802455

Umm Al-Qura University Electrical Engineering
Department
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What is an embedded system?

• General-purpose computer, such as a personal
  computer (PC), is designed to be flexible and to
  meet a wide range of end-user needs (today, there
  is a huge number of end-user applications running
  on PC).
• In contrast, embedded system is a special-purpose
  computer which is designed to perform a small
  number of dedicated functions (tasks) for a
  specific application.

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What is the embedded part?

• An embedded system might contain one or more
  programmable chips such as a microcontroller (µC,
  uC or MCU), microprocessor or digital signal
  processor.
• The word embedded indicates that the computer
  unit (e.g. microcontroller) is fully surrounded
  by the device it controls, and is invisible to
  the user of the device.

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Components of embedded system

• An embedded system usually consists of hardware,
  software and perhaps mechanical or other
  components, and can be a small part of a larger
  system or machine.
• Embedded systems combine elements of hardware and
  software, semiconductor technology, analog and
  digital electronics, computer architecture,
  sensors and actuators, and more.

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Interfacing with environment

• In desktop computer systems, the user usually
  interacts with the software application through a
  set of highly-capable input / output devices such
  as keyboard, mouse, and coloured screen.
• In contrast, embedded systems have no
  sophisticated interface devices instead, they
  interact with the surrounding environment through
  a set of simple components such as switches,
  small keypads, light-emitting diodes (LEDs) and
  so on.

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Role of embedded systems

• People in the 21st century may not realise that,
  without the emergence of embedded technology,
  their life would have become harder. This is
  because most electrical devices people use
  nowadays are utilising embedded systems.
• Examples of such devices are microwave ovens,
  TVs, VCRs, DVDs, mobile phones, MP3 players,
  washing machines, air conditions, handheld
  calculators, printers, digital watches, digital
  cameras, automatic teller machines (ATMs) and
  medical equipments.

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Basic examples of embedded systems
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The need for embedded systems?

• In a publication by ABB Corporate Research
  (2006), Christoffer Apneseth reports that the
  need for embedded microprocessors arises mainly
  because
• General-purpose computers, like PCs, generally
  exceed the cost of the majority of products that
  utilise embedded systems, and
• General-purpose systems are not capable of
  meeting the requirements that embedded systems
  should have such as reliability, product size
  limitation, real-time performance and
  power-consumption constraints.

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What is simply the reliability?

• Reliability simply means
• The ability to provide the service to the user
  whenever requested.
• The ability of a person or system to perform and
  maintain its functions in routine circumstances,
  as well as unexpected circumstances.
• In engineering, reliability is the ability of a
  system or component to perform its required
  functions under stated conditions for a specified
  period of time.

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Historical Background

• The first computer system, recognised as an
  embedded system, was the Apollo Guidance Computer
  developed in 1959 to control the Apollo
  spacecraft.
• The first successful commercial minicomputer was
  the PDP-8 produced by Digital Equipment
  Corporation in 1965.
• In 1971, Intel released the first commercial
  single-chip microprocessor, the Intel 4004, which
  was primarily used in calculators and small
  systems.

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Historical Background (Cont.)

• External memory and support chips were required
  with the microprocessor unit until 1980s, when
  microcontrollers were developed to integrate all
  components of a microprocessor system into a
  single chip.
• Since then, many commercial companies began the
  development of embedded microcontrollers to meet
  the increasingly growing demand of modern
  technology.

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Microcontrollers companies / families

• Examples of companies producing microcontrollers
  are Atmel, Philips, Intel, Infineon, Texas
  Instruments, Microchip and Motorola.
• Examples of microcontroller families used in the
  design of embedded systems are 8051, ARM, PIC,
  MIPS, PowerPC, Atmel AVR, MPC555 and C16x.

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Embedded Systems Market

• In 2002, Ludwig D.J. Eggermont (STW Technology
  Foundation) estimated the embedded systems market
  size as100 times larger than the size of desktop
  (PC) market.
• In 2003, Bas Graaf (IEEE Software) forecasted
  this market size to grow exponentially within the
  next ten years.

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Global embedded systems market trend
(Source BBC Research Group, 2005)
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Safety-critical systems

• Form safety point of view, there are two types of
  embedded systems
• Non-critical systems.
• Critical systems.
• In safety-critical systems, failures can have
  very serious impacts on human safety.
• For example, incorrect operation of such systems
  may endanger human lives or cause catastrophic
  consequences.

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Safety-critical systems (Cont.)

• Safety-critical systems are typically used in the
  development of aerospace, automotive, railway,
  military and medical applications.
• The utilisation of embedded systems in
  safety-critical applications requires that the
  system should have real-time operations to
  achieve correct functionality and/or avoid any
  possibility for detrimental consequences.

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Real-time systems

• Real-time systems are computer systems which must
  react (respond) to events in the environment
  within limited time boundaries.
• Real-time behaviour can only be achieved if the
  system is able to perform predictable and
  deterministic processing.

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Real-time systems (Cont.)

• A given system is described as real-time if it is
  able to complete the execution of particular
  activities within specific time intervals.
• The system should guarantee that a particular set
  of activities will always be completed within
  (for example) 4 ms or at precisely 3 ms periods
  (e.g. calculating the required throttle settings
  to control speed in an auto-driver system) .

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Real-time systems (Cont.)

• In situations where the system is unable to meet
  these time constraints (requirements), then the
  whole application is not simply slower than would
  be expected, it tends to be entirely useless.
• As a result, the correct behaviour of a real-time
  system depends on
• The logical correctness of the output results.
• The time at which the results are produced.

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Real-time systems (Cont.)

• Real-time systems are divided into two main
  classes
• Soft-real-time where timing constraints should
  be generally met, and failure to do so may only
  result in reduced system performance but does not
  cause serious damages or jeopardise correct
  behaviour.
• Hard-real-time systems where timing constraints
  must be deterministically met in order to
  achieve correct operations or avoid harmful
  consequences.

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Brake-by-Wire system

• The BBW system is a brake system based on
  controlling the electric brake system in each
  wheel by electric signal.
• This BBW system can significantly improve the
  brake performance compared with traditional brake
  systems using hydraulic power.
• This BBW system also helps to increase fuel
  efficiency.

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Brake-by-Wire system (Cont.)
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Brake-by-Wire system (Cont.)

• Brake-by-Wire system is designed for modern
  passenger cars.
• The brake actuators are required to respond
  within a fixed amount of time after the brake
  pedal is pressed.
• If the system fails to respond within this time
  frame, then there could be a danger that the
  vehicle may not stop in time before crashing into
  another vehicle, causing serious damage and
  possibly losses in passenger lives.

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Aircraft auto-pilot system

• In the aircraft auto-pilot system, rapid
  reactions are necessarily required to keep the
  aircraft staying on its path.
• Reactions include rudder, elevator, aileron and
  engine settings.
• If the system cannot adjust the rudder setting in
  millisecond time-scale (for example), the plane
  may oscillate unpleasantly or even crash in more
  severe circumstances.

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Aircraft auto-pilot system (Cont.)
Image courtesy of Bill Harris
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Aircraft auto-pilot system (Cont.)
Image courtesy of Bill Harris
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Aircraft auto-pilot system (Cont.)
Image courtesy of Bill Harris
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Predictability

• In real-time applications, it is important to
  predict the timing behaviour of the system to
  guarantee that
• The system will behave correctly.
• Life of the people using the system will be
  saved.
• While the most important property of a desktop
  computing system is its speed, the most important
  property in a real-time computing system is
  predictability.

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Predictability (Cont.)

• Giorgio Buttazzo states that
• rather than being fast, a real-time computing
  system should be predictable .
• Hence, predictability is an important
  characteristic in real-time embedded systems.

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Predictability (Cont.)

• Predictability is
• In general the ability to forecast (or
  anticipate) what will happen in the future.
• For systems the ability to determine, in
  advance, exactly what the system will do at every
  moment of time in which it is running, hence,
  determine whether the system is capable of
  meeting all its timing constraints.
• Therefore, building an embedded application with
  highly predictable system behaviour is a non
  straightforward process.

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Challenges in building predictable embedded
systems

• Embedded systems engineering can be viewed as a
  branch of systems engineering discipline.
• Engineers are concerned with all aspects of the
  system development including hardware and
  software engineering.
• Activities such as specification, design,
  implementation, testing, operation and
  maintenance are all involved in the development
  of an embedded application.

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Challenges in building predictable embedded
systems (Cont.)
Development Life Cycle (Waterfall Model)
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Challenges in building predictable embedded
systems (Cont.)
Development Life Cycle (Waterfall Model)
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Challenges in building predictable embedded
systems (Cont.)

• Requirements specifications
• A design of any system usually starts with ideas
  in peoples mind.
• These ideas need to be captured in requirements
  specifications documents that specify
• The basic functions of the system.
• The desirable features of the system.

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Challenges in building predictable embedded
systems (Cont.)

• System and Software Design
• After the requirements specifications are
  documented correctly, design process begins.
• The design process determines how the system
  functions and features can be achieved by the
  system components (hardware and software).
• Design is usually based on modelling.

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Challenges in building predictable embedded
systems (Cont.)

• Implementation
• Implementation is the process of converting
  design elements into a hardware system and / or
  software system (executable source code).
• If commercial off the shelf (COTS) uCs are
  used, then developers will mainly focus on
  software implementation.
• Selection of the programming language to program
  the uC is made in this stage (e.g. Assembly, Ada,
  C or many other languages).

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Challenges in building predictable embedded
systems (Cont.)

• Integration and Testing
• All system units are put together (integrated).
• The complete system is tested (verified) to
  ensure that it functions as required.

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Challenges in building predictable embedded
systems (Cont.)

• Operation and Maintenance
• After integration and testing, the system becomes
  operational.
• In system maintenance, periodic checks are
  carried out to ensure high quality and correct
  functionality of the system.

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Challenges in building predictable embedded
systems (Cont.)

• Ensuring predictability, whilst moving between
  the various development stages, requires further
  techniques to be applied at different stages
  throughout the whole development process.
• Giorgio Buttazzo states that
• one safe way to achieve predictability is to
  investigate and employ new methodologies at every
  stage of the development of an application, from
  design to testing.

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Validation and Verification

• There are two main processes to evaluate the
  operation of any software-based system
• Validation to ensure that the right system is
  built.
• Verification to ensure that the system is built
  right.

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Validation and Verification (Cont.)

• Validation is
• The process of evaluating software at the end of
  the development process to ensure compliance with
  software requirements.
• A general process which checks the consistency of
  the system as a whole with its requirements.
• Determination of the correctness of the final
  program or software produced from a development
  project with respect to the user needs and
  requirements.

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Validation and Verification (Cont.)

• Verification is
• The process of evaluating a system or component
  to determine whether the products of a given
  development phase satisfy the conditions imposed
  at the start of that phase.
• The demonstration of consistency, completeness,
  and correctness of the software at each stage and
  between each stage of the development life cycle.
• Verification is a detailed process which must be
  applied at each stage in the software development
  process to check the conformance of that stage
  with its predefined specification.

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Validation and Verification (Cont.)

• Validation is a general process which shows that
  the software meets the customer needs, while
  verification is the process which ensures that
  the software conforms to its specification.
• Validation usually takes place at the end of the
  development cycle, and looks at the complete
  system as opposed to verification, which focuses
  on smaller sub-systems.
• Validation is usually accomplished by verifying
  each stage of the software development life
  cycle.
• Validation can be viewed as end-to-end
  verification process

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Validation and Verification (Cont.)
The system development life cycle.
Integrating validation and verification in the
system development life cycle.
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Validation and Verification (Cont.)

• Validation and verification processes are used to
  check both the functional and non-functional
  requirements of the system.
• Functional requirements relate to the behaviour
  of the system.
• Non-functional requirements relate to the quality
  attributes of the system (non-behavioural
  requirements).
• Predictability is classified as non-functional
  requirement.
• Non-functional requirements also include,
  scalability, efficiency, reliability, usability,
  stability, and many others.