ELCT 912: Advanced Embedded Systems - GUCeee.guc.edu.eg/Courses/Electronics/ELCT912 Advanced...

ELCT 912:Advanced Embedded Systems

Lecture 1: Introduction

Dr. Mohamed Abd El Ghany, Department of Electronics and Electrical Engineering

[email protected]

Administrative Rules

� Course components:� Lecture: Wednesday (First slot), 8:30-10:00 (H10)� Office Hours: Thursday after lecture

� Teaching assistant: ----

� Grading:� Assignments: 20%� Project : 20%� Mid term exam: 20%� Final exam: 40%

2Dr. Mohamed Abd el Ghany Department of Electronics and Electrical Engineering

ELCT 912: Advanced embedded Systems Winter 2011

Administrative Rules

� Assignments � Project:

� Announcement : Thursday, 29/10/2011� Due date: 21/12/2011Due date: 21/12/2011



Course Policies

� Take notes during the lectures, Don’t expect that everything said during the lecture will be documented in the slides

� I expect that anything “said” during a lecture � I expect that anything “said” during a lecture or tutorials will be known by all students. So, if you don’t attend, then please “at least” ask!

� It is your responsibility to check the course website regularly for any announcements or material



Course Objective

� Understanding the constraints and characteristics of embedded systems

� Understanding the hardware/software trade-offs inherent in embedded systems

Understanding the particular requirements of real-time � Understanding the particular requirements of real-time systems

� Applying this understanding to carry out the design process

� Developing assembly and C programs to control embedded systems



Text and Reference Books

� P. Marwedel: Embedded System Design, Springer, 2006

� T. Noergaard, “Embedded systems Architecture” Elsevier Inc. 2005, ISBN: 0-7506-7792-9

� W. Wolf, “Computers as Components: Principles of Embedded Computing system Design,” 2nd Edition, Morgan Kaufman Publishers, 2008

� A. N. Sloss, D. Symes, and C. Wright, “ ARM System Developers’ Guide,” ISBN: 1- 55860-874-5



Prerequisites

�Digital Logic Design�Electric Circuits I, II�Introduction to Computer

Programming



What is a real-time system?

� Frequently embedded systems are real-time in nature

� A real-time system is any information processing system which has to respond to externally generated input stimuli within a finite and specified period

� the correctness depends not only on the logical results but also the time it was delivered

� Failure to respond is as bad as the wrong response!



Application areas and examples

Automotive electronics

Avionics

Security

Consumer electronics

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Railways

Telecommunication

Health Sector

Fabrication equipment

Smart building

Robotics

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Generalized Embedded System

� Computer is interfaced directly to real-world physical equipment

� Physical equipment controlled through regularly sampling measurement devices

System software modules reflect physical nature of


� System software modules reflect physical nature of environment� Module for physical control of devices� Module to record system changes� Module to retrieve & display changes� Module to interact with operator


A Typical Embedded System



Embedded vs. Conventional Systems – Hardware

� Computer hardware for embedded applications consists of fairly standard components – e.g.� Processors � Memory units


� Memory units� Buses & peripheralsplus

� Real-time I/O devices, e.g. sensors & actuators


Embedded vs. Conventional Systems – software: Correctness

Embedded software differs from conventional software: program must be both logically & temporally correct

� Software must satisfy timing assertions on relation over relative & absolute times – e.g. deadlines – a limit on (relative or absolute) time when a computation must


(relative or absolute) time when a computation must complete

� Distinction between hard & soft real-time systems� Hard – must meet timing constrains, else system fails;

e.g. system that controls vertical motion of a lift� Soft – considered successful despite missing some

timing constraints; performance may deteriorate; e.g. failed phone connection


Embedded vs. Conventional Systems – software: Concurrency

Embedded software must deal with inherent physical concurrency – part of the external world to which they’re connected

� Signals from environment can arrive simultaneously, disjoint but parallel activities may be monitored/


disjoint but parallel activities may be monitored/ controlled by a signal computer system & output signals may need to be emitted at the same time (timing constraints)

� Complexity of system design increases because of combination of concurrency and timing problems


Embedded vs. Conventional Systems – software: Reliability

Reliability & Fault Tolerance issues are particularly significant

� Reliability –measure of how often a system will fail, or the probability that it will perform correctly over a given period of time.


period of time.However, no system is perfectly reliable, so must be able to cope with failures - e.g. mission failures, loss of human life or money can be very costly

� Fault Tolerance - concerned with recognizing & handling failures; avoid failures where possible, else fail gracefully with as little cost as possible


Embedded vs. Conventional Systems – software: Criticality

Criticality – measure of the cost of failure

� Higher the cost of failure, the more critical the systeme.g. - aircraft or nuclear power plant controller are highly

critical systems


� Communication frequently non-critical e.g. mobile phone

� Differentiate hardness & criticality (often go together) -not meeting a constraint may cause system failure, but failure may not be critical


Embedded vs. Conventional Systems –software: Application Specific

Most conventional computer systems are general-purpose – i.e. run several applications at the sametime

� Embedded systems, on the other hand, are application-specific & often standalone - all s/w


application-specific & often standalone - all s/w including OS is tailor-made for the particular system

� Many embedded systems have a human operator who interactively controls & monitors it - human-machine interface design must prevent errors & confusion


Embedded vs. Conventional Systems –software: Testing

Testing & Validation - due to high costs of failures, itis often impossible to test & validate systems intheir environments, but rely on

� simulations


� testing of subsystems

� careful specifications & comprehensive analysis of designs

� run-time procedures for fault detection & handling


Interaction with Hardware Devices

� Embedded systems require components to interact with environmental devices through sensors & actuators

� Computer interface is through input & output registers -operation is device & system dependent


operation is device & system dependent

� Devices can also generate interrupts to signal the processor

� Control of devices must often be direct (not through OS) because of time-criticality

� Interfacing to devices considered laterELCT 912: Advanced embedded Systems Winter 2011

Generic Embedded Hardware Configuration

� Comprises several nodes connected by a communications network

� Significant - presence of sensors, actuators, displays, precise clocks & timers


� For the purpose of timing prediction, behavior of virtual memories, instruction & data caches must predictable

� System should provide both polling & priority interrupts for sensors, actuators & I/O devices




Generic network

Generic node



� Resource sharing between processors & I/O devices can cause unpredictable performance

� Programs can be organized so that processors & I/O don’t access same memory locations simultaneously

More difficult to guarantee deterministic timing over a


� More difficult to guarantee deterministic timing over a comms. network

� Message transmission times unpredictable because of transmission path or medium multiplicity, or shared network

� H/W reliability within and between nodes obtained through redundancy


Software Life-cycle of Embedded Systems

� Life Cycle - similar to standard software engineering

� Classified into six sequential phases or tasks1. Concept - determination of project needs & goals2. Requirements - what the software must do3. Design - how S/W will meet its requirements


3. Design - how S/W will meet its requirements4. Implementation - programming the application5. Testing - set of independently developed test cases are

used to verify that system meets requirements6. Maintenance - additions, deletions & modifications due

to changing conditions

� Feedback loops connect the phasesELCT 912: Advanced embedded Systems Winter 2011

Concept Phase

� Determine project goals & needs - driven by customer input, technology changes & marketing decisions

� Includes feasibility studies


� Includes feasibility studies

� By-product of stage - often a white paper, detailing what to build, and justifying the project & its feasibility


Requirements Phase

� Formal requirements specification about interfaces, functions, timing & physical constraints, such as, mass, power, voltage, etc.

� Does not specify how to meet requirements, but may specify budget & schedule


specify budget & schedule

� Test requirements committed to a test plan (used to generate test cases in stage 5)

� Forms the contract if customer & designer are different


Requirements Phase

� Functional Requirements - features which can be tested by exercising the system

� Non-functional Requirements - specification about processor type, implementation language, methodology, version control, documentation, maintainability, modularity,


version control, documentation, maintainability, modularity, schedule, etc.

� Chief goals of phase –� Define H/W & S/W interfaces� Write requirements document� Write test plan� Prepare project schedule & budget


Design Phase

� Converts requirements document into a detailed specification called detailed design document

� Specifies how requirements are to be met by partitioning functional features into H/W or S/W modules


modules

� Design phase often finds problems in the requirements document, such as, conflicts, redundancies or technological difficulties

� Requirements document may need to be modified -e.g. exempt certain requirements


Design Phase – Major Tasks

� Partition system into modules whose implementation is clear

� Allocate modules to H/W or S/W

� Prepare detailed design document


� Prepare detailed design document

� Develop specific test cases


Implementation Phase

� Implement modules detailed in design phase - programs for S/W, circuits for H/W - implemented concurrently

� Phase ends when all modules implemented & integrated

� Tools (e.g. CASE) can be used to manage software development


development

� Major Tasks –� Code S/W & build H/W modules� Debug S/W & H/W and integrate modules� Developed automated test cases


Testing Phase

� Testing, in order to debug software, occurs throughout implementation phase

� Testing phase is a formal step where a set of independently developed test cases are used to verify that system meets its requirements


that system meets its requirements

� System cannot be changed in this phase - if it fails, has to be redesigned and then completely re-tested

� Main tasks in this phase - perform system validation & prepare test reports


Maintenance Phase

� Phase consists of:� Product deployment� Customer support� Continuing system error correction� Release control


� Release control

� Phase ends when product is no longer required

� Each of these 6 stages is very similar to standard SE. However, partitioning between hardware and software is an additional requirement.

� Testing of increased importanceELCT 912: Advanced embedded Systems Winter 2011

Embedded System Architecture

FPGA/ASIC Memory

CPUADC DAC

Software

Sensors Actuators


Microcontroller

Diagnostic Tools

Human Interface

Auxiliary Systems (Power, Cooling)

Electro-mechanical backup & Safety

External Environment


Challenges in Embedded System Design

� Embedded systems really must be dependable.

� Due to efficiency targets, software designs cannot be done independently of the underlying hardware. Therefore, software and hardware must be taken into account during the design steps. Many objectives must be taken into


the design steps. Many objectives must be taken into account during the design. Just capturing non-functional requirements is already difficult.

� The link to physics has additional implications. For example, we must check if we will definitely meet real-time constraints. Managing time is one of the largest challenges


Challenges in Embedded System Design

� Real systems are profoundly concurrent. Managing concurrency is therefore another major challenge.

� Real embedded systems are complex. Therefore, they comprise various components and we are interested in compositional design.


compositional design.

� Traditional sequential programming languages are not the best way to describe concurrent, timed systems.


Summary

� Strong link between embedded and real-time systems

� Hard vs soft real-time

� Embedded software has additional characteristics including complexity, reliability, concurrent and real-time control.


� Have to consider interaction with hardware interfaces,

� Software design cycle same as standard SE with added complexity

� Efficient implementation important for many embedded devices.


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