Chapter: Embedded Systems
Embedded System : An Introduction
EMBEDDED
SYSTEM : AN INTRODUCTION
Unit
Structure
Objectives
1Introduction
2 Definition
of Embedded System
3 History of Embedded System
4Embedded System & General purpose computer
5Classification of Embedded System
6Application of Embedded System
0 OBJECTIVES
To understand what is an Embedded System and then define it
Look at embedded systems from a historical point of view
Classify embedded systems
Look at certain applications & purposes of embedded systems
1. INTRODUCTION
This chapter introduces the reader to the world
of embedded systems. Everything that we look around us today is electronic. The
days are gone where almost everything was manual. Now even the food that we eat
is cooked with the assistance of a microchip (oven) and the ease at which we
wash our clothes is due to the washing machine. This world of electronic items
is made up of embedded system. In this chapter we will understand the basics of
embedded system right from its definition.
An
embedded system is a combination of 3 things:
Hardware
Software
Mechanical
Components
And it is
supposed to do one specific task only.
Example
1: Washing Machine
A washing machine from an embedded systems point
of view has:
Hardware: Buttons,
Display & buzzer, electronic circuitry.
Software:
It has a chip on the circuit that holds the software which drives controls
& monitors the various operations possible.
Mechanical
Components: the internals of a washing machine which actually wash the clothes
control the input and output of water, the chassis itself.
Example
2: Air Conditioner
An Air Conditioner from an embedded systems
point of view has:
Hardware:
Remote, Display & buzzer, Infrared Sensors, electronic circuitry.
Software:
It has a chip on the circuit that holds the software which drives controls
& monitors the various operations possible. The software monitors the
external temperature through the sensors and then releases the coolant or
suppresses it.
Mechanical
Components: the internals of an air conditioner the motor, the chassis, the
outlet, etc
An embedded system is designed to do a specific
job only. Example: a washing machine can only wash clothes, an air conditioner
can control the temperature in the room in which it is placed.
The hardware & mechanical components will
consist all the physically visible things that are used for input, output, etc.
An embedded system will always have a chip
(either microprocessor or microcontroller) that has the code or software which
drives the system.
3 HISTORY
OF EMBEDDED SYSTEM
The first
recognised embedded system is the Apollo Guidance Computer(AGC) developed by
MIT lab.
AGC was
designed on 4K words of ROM & 256 words of RAM.
The clock
frequency of first microchip used in AGC was 1.024 MHz.
The
computing unit of AGC consists of 11 instructions and 16 bit word logic.
It used
5000 ICs.
The UI of
AGC is known DSKY(display/keyboard) which resembles a calculator type keypad
with array of numerals.
The first
mass-produced embedded system was guidance computer for the Minuteman-I missile
in 1961.
In the
year 1971 Intel introduced the world's first microprocessor chip called the
4004, was designed for use in business calculators. It was produced by the
Japanese company Busicom.
4 EMBEDDED SYSTEM
& GENERAL PURPOSE COMPUTER
The
Embedded System and the General purpose computer are at two extremes. The
embedded system is designed to perform a specific task whereas as per
definition the general purpose computer is meant for general use. It can be
used for playing games, watching movies, creating software, work on documents
or spreadsheets etc.
Following are certain specific points of
difference between embedded systems and general purpose computers:
5
CLASSIFICATION OF EMBEDDED SYSTEM
The classification of embedded system is based
on following criteria's:
On generation
On complexity &
performance
On deterministic
behaviour
On triggering
On generation
First generation(1G):
Built
around 8bit microprocessor & microcontroller.
Simple in
hardware circuit & firmware developed.
Examples:
Digital telephone keypads.
Second generation(2G):
Built
around 16-bit µp & 8-bit µc.
They are
more complex & powerful than 1G µp & µc.
Examples:
SCADA systems
Third generation(3G):
Built
around 32-bit µp & 16-bit µc.
Concepts
like Digital Signal Processors(DSPs), Application Specific Integrated
Circuits(ASICs) evolved.
Examples:
Robotics, Media, etc.
Fourth generation:
Built
around 64-bit µp & 32-bit µc.
The
concept of System on Chips (SoC), Multicore Processors evolved.
Highly
complex & very powerful.
Examples:
Smart Phones.
On complexity & performance
1. Small-scale:
Simple in
application need
Performance
not time-critical.
Built
around low performance & low cost 8 or 16 bit µp/µc.
Example:
an electronic toy
Medium-scale:
Slightly
complex in hardware & firmware requirement.
Built
around medium performance & low cost 16 or 32 bit µp/µc.
Usually
contain operating system.
Examples:
Industrial machines.
Large-scale:
Highly
complex hardware & firmware.
Built
around 32 or 64 bit RISC µp/µc or PLDs or Multicore Processors.
Response
is time-critical.
Examples:
Mission critical applications.
On deterministic behaviour
This
classification is applicable for “Real Time” systems.
The task
execution behaviour for an embedded system may be deterministic or
non-deterministic.
Based on
execution behaviour Real Time embedded systems are divided into Hard and Soft.
On triggering
Embedded
systems which are “Reactive” in nature can be based on triggering.
Reactive
systems can be:
Event
triggered
Time
triggered
6
APPLICATION OF EMBEDDED SYSTEM
The application areas and the products in
the embedded domain are countless.
Consumer Electronics: Camcorders, Cameras.
Household appliances: Washing machine,
Refrigerator.
Automotive industry: Anti-lock breaking
system(ABS), engine control.
Home
automation & security systems: Air conditioners, sprinklers, fire alarms.
Telecom: Cellular phones, telephone switches.
Computer
peripherals: Printers, scanners.
Computer networking systems: Network routers
and switches.
Healthcare: EEG, ECG machines.
Banking & Retail: Automatic teller
machines, point of sales.
Card
Readers: Barcode, smart card readers.
7
PURPOSE OF EMBEDDED SYSTEM
Data Collection/Storage/Representation
Embedded
system designed for the purpose of data collection performs acquisition of data
from the external world.
Data
collection is usually done for storage,analysis, manipulation and transmission.
Data can
be analog or digital.
Embedded
systems with analog data capturing techniques collect data directly in the form
of analog signal whereas embedded systems with digital data collection
mechanism converts the analog signal to the digital signal using analog to
digital converters.
If the
data is digital it can be directly captured by digital embedded system.
A digital
camera is a typical example of an embedded
System
with data collection/storage/representation of data.
Images are
captured and the captured image may be stored within the memory of the camera.
The captured image can also be presented to the user through a graphic LCD
unit.
Data communication
Embedded
data communication systems are deployed in applications from complex satellite
communication to simple home networking systems.
The
transmission of data is achieved either by a wire-line medium or by a wire-less
medium.
Data can
either be transmitted by analog means or by digital means.
Wireless
modules-Bluetooth, Wi-Fi.
Wire-line modules-USB,
TCP/IP.
Network
hubs, routers, switches are examples of dedicated data transmission embedded
systems.
Data signal processing
Embedded
systems with signal processing functionalities are employed in applications
demanding signal processing like speech coding, audio video codec, transmission
applications etc.
A digital
hearing aid is a typical example of an embedded system employing data
processing.
Digital
hearing aid improves the hearing capacity of hearing impaired person
Monitoring
All embedded
products coming under the medical domain are with monitoring functions.
Electro
cardiogram machine is intended to do the monitoring of the heartbeat of a
patient but it cannot impose control over the heartbeat.
Other
examples with monitoring function are digital CRO, digital multi-meters, and
logic analyzers.
Control
A system with control functionality contains
both sensors and actuators.
Sensors are connected
to the input port for capturing the changes in environmental variable and the
actuators connected to the output port are controlled according to the changes
in the input variable.
Air conditioner system
used to control the room temperature to a specified limit is a typical example
for CONTROL purpose.
Application specific user interface
Buttons, switches,
keypad, lights, bells, display units etc are application specific user
interfaces.
Mobile phone is an
example of application specific user interface.
In mobile phone the
user interface is provided through the keypad, system speaker, vibration alert
etc.
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