EMBEDDED SYSTEM : AN INTRODUCTION
2 Definition of Embedded System
3 History of Embedded System
4Embedded System & General purpose computer
5Classification of Embedded System
6Application of Embedded System
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
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:
And it is supposed to do one specific task only.
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 complexity & performance
On deterministic behaviour
Built around 8bit microprocessor & microcontroller.
Simple in hardware circuit & firmware developed.
Examples: Digital telephone keypads.
Built around 16-bit µp & 8-bit µc.
They are more complex & powerful than 1G µp & µc.
Examples: SCADA systems
Built around 32-bit µp & 16-bit µc.
Concepts like Digital Signal Processors(DSPs), Application Specific Integrated Circuits(ASICs) evolved.
Examples: Robotics, Media, etc.
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
Simple in application need
Performance not time-critical.
Built around low performance & low cost 8 or 16 bit µp/µc.
Example: an electronic toy
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.
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.
Embedded systems which are “Reactive” in nature can be based on triggering.
Reactive systems can be:
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
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.
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
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.
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.