Embedded Systems - Brief Intro

8/3/2019 Embedded Systems - Brief Intro

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K Raghu Nathan 1

A Brief Introduction to

Embedded Systems

K. RaghunathanChartered Engineer

FIETE, MIE, MCSI, MISTE, MISTD. MIIMM

Retd. Dy. Controller (R&D)


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Embedded Systems

Overview of Embedded Systems

Embedded System Design

Embedded System Designer

More Knowledge


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What is an Embedded System ?

Examples of Embedded Systems

Why an Embedded System ?

Salient Features


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What is an Embedded System ?

A computer system, fitted as part of some

Equipment which is not a computer

The whole system is not called a computer - it isknown by the name of the Equipment

The embedded computer system controls the

equipment in which it is embedded

Performs only specific tasks, often in real-time


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Network Printer Network Interfacing & Routing

Handheld Barcode Scanner Conversion of Image to Number

Mobile Phone with Internet Connectivity Browsing, eMail, FTP, Chat etc


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CNC Machines & Robots Control the Sequence of Operations

Satellites Remote-sensing, Data-formatting,

Communication, Navigation Control etc

Televison Set Digital on-screen display of menu, channel

number, subtitles etc Washing Machines Control of Sequence of Operations, Motor

speed & duration control etc


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Why embed a Computer ?

Computers are more suitable for

Control Data Processing Decision Making Digital Communication


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Why embed a Computer ?

Main Equipment is Larger & Costlier;

computer is smaller, cheaper & used for

only some specific purpose

Using General-purpose computer involvesadditional space & wiring. It is better to fit a

small computer inside [or onto] the

equipment itself often, main equipment itself may have to

be small & portable


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Salient Features of Embedded Systems

Purpose & Functionality Specific Purpose; Limited Functionality

Size

Small enough to fit into/onto the main eqpt Real-Time

Response within a specified Time-limit

I/O Devices Very Few; only a set of Sensors & Activators Conspicuous absence of conventional devices

like keyboard, CRT screen, hard disk etc


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Embedded Systems




More Knowledge


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Selection of CPU & other Hardware Design of the Hardware System

Design & Development of Software Testing & Debugging Loading the Software into the Embedded

Systems Memory


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Selection of CPU & other Hardware

CPU Speed

Instruction Set Multitasking Capabilities Interrupt- handling Capabilities Power Consumption

Heat Dissipation


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Memory

Non-Volatile[ROM/PROM/EPROM] Code

Fixed Data Look-Up Tables, Constants, Initial Values of

Variables

Volatile[RAM] Variable Data temporary data


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I/O Devices

Depends on : Main Equipment & its purpose/functions Purpose to be served by the embedded

system

May also need : HW & SW Interfaces or Drivers for the i/o

devices


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Software Development

Software has to be developed on some

other convenient computer system [Host

System]

The Code obtained in the Host system

should run in the Embedded System

[Target System]


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HW configuration of Host & Target will be

different

Should use Cross Compilers & CrossAssemblers on the Host, to get Target Systems

Machine Code as the Output

Often, an RTOS [Real Time Operating System] is

used


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Usually the SW is developed as a set of

Tasks [functions/procedures] & ISRs

[Interrupt Service Routines]

Tasks perform some specific actions most likely, some of the primary functions of

the Main eqpt

ISRs interrupt running Tasks based oncertain events [inputs from sensors] to take appropriate action for those inputs to update data for the tasks


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Testing & Debugging

Often not possible to test the program by

actually loading it into the target system &

running it in the Main eqpt

So, code has to be tested in the Hostsystem itself

Need Emulators which can emulate the

embedded systems CPU


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Testing & Debugging

Drivers & Scaffolds to be written to simulate actual inputs & behaviour of the

main eqpt

Test Data normally expected range of values

out-of-range values erroneous data


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Loading SW in the Embedded

Systems Memory

No operating system in the embedded

system

Code generated on the Host systemshould include start-up [initialising] routines

for the target system Use of RTOS ensures automatic addition

of start-up code


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Loading SW in the Embedded

Systems Memory

Special programs calledLocatorsenabledeveloper to specify which blocks of code should

be loaded at what addresses in the embedded

systems memory Output of Locator is in the form of a file stored in

the Host; this file will have a special format [not

the standard executable file you get in desktop

systems] Special programs called Loaders

understand the Locators file format load the code in embedded systems memory


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Tools for Embedded Software

Development

Cross Compilers Cross Assemblers

Locators

RTOS

Loaders


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RTOS

Cross-Compiler with extra features Easier Development Environment Produce Machine Code of Target CPU

Automatic inclusion of Start-up Code Many RTOSes available

iRMX86, uC-OS, VxWorks, pSOS, QNX etc

Many of them written in C/C++ allow us to develop programs using C/C++


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Hardware Design Considerations

Physical Size Small

Power Consumption Low

Heat Dissipation Very Low

Cost Low cost, without compromising Quality &

Performance


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Software Design Considerations

Real Time Response No part of the code can take unpredictable

execution time

ISRs must be kept short No Dead-Locks or Circular Waits

Reliability Should run without Human Intervention

Should NOT Crash Robust & Fault Tolerant Exception Handling without Malfunction or

unpredictable behaviour


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Embedded Systems




More Knowledge


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Specialist Knowledge of Theory & Practical

Techniques of both Hardware & Software

Strong Foundation in Digital Logic Ckts, ADCs, DACs, PLCs, FPGAs Microcontrollers & Interfacing TechniquesAssembly Language Programming High Level Language Programming [C/C++] Writing ISRs RTOS


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Job Oppurtunities

Employers Manufacturers of

Telecom Products

Automatons & Industrial Robots Automated Production & Diagnostic Eqpt

Software Development Firms

Remuneration Lucrative


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Embedded Systems




More Knowledge


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For More Knowledge

Books

Hands-on Training


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Books on Embedded Systems

An Embedded System Primer David E Simon

Embedded System Design Steve Heath

The Art of Programming Embedded Systems Jack G Ganssle

Fundamentals of Embedded Software - Where C and

Assembly Meet Daniel W Lewis

Real Time Systems & Programming Languages Alan Burns & Andy Wellings Real Time Programming

Moore Grehan


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Training on Embedded Systems

TCIL, & their Branches & Franchisees Telecom Consultants India Ltd formed by DoT

ECIL, Hyderabad Electronic Corporation of India Ltd

Many institutes boast of embedded system

training teach only soldering & assembling using kits do not teach theory or design


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Thank You !

Embedded Systems - Brief Intro

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