Embedded System
Unit-1
Introduction
What is embedded system?
An embedded system is some combination of computer hardware and software, either fixed in capability or programmable, that is designed for a specific function or for specific functions within a larger system. Industrial machines, agricultural and process industry devices, automobiles, medical equipment, cameras, household appliances, airplanes, vending machines and toys as well as mobile devices are all possible locations for an embedded system.
An embedded system has three components :−
• It has hardware.
• It has application software.
• It has Real Time Operating system (RTOS)
Advantages
• Easily Customizable
• Low power consumption
• Low cost
• Enhanced performance
Disadvantages:
• High development effort
• Larger time to market
Characteristics of an Embedded System
• Single-functioned :−
An embedded system usually performs a specialized operation and does the same repeatedly.
• Reactive and Real time :−
Many embedded systems must continually react to changes in the system's environment and must compute certain results in real time without any delay.
• Microprocessors based :−
It must be microprocessor or microcontroller based.
• Memory :−
It must have a memory, as its software usually embeds in ROM. It does not need any secondary memories in the computer.
• Connected :−
It must have connected peripherals to connect input and output devices.
• HW-SW systems :−
Software is used for more features and flexibility. Hardware is used for performance and security.
Types of Embedded system:
Embedded system can be classified into different types based on performance function requirement and performance of the microcontroller.
Real time embedded system :
An embedded system that gives an output within a specified amount of real time is called real time embedded system. That is in additional to a proper output it depends on time constant as well.
Stand Alone embedded system:
These are embedded system that can work by themselves. In other words they are self sufficient and don't required a different system to function. Music players, video gaming and microwave ovens are the examples of standalon system.
• Network embedded system:
Embedded system that are connected to the network & depends on it from their functionally are called network embedded system. Router home security system are network embedded system.
• Mobile embedded system
Embedded system that are mobile in nature are called mobile embedded system. They include generally small system. They are used in portable embedded devices like cell phones, mobile, digital camers, mp3 player and personal digital assistant.
Apllication of embedded system:
Here are some application area of embedded system:
• Consumer electronics:
Mobile phones , video games, printers, home entertainment system, television, digital camera, music player
• Household application:
Washing machine , diswashes, air conditioner, etc
• Medical equipment:
BLood pressure monitor, CET scanner, heart beat monitor, ECG machine, etc
• Automobiles
Anticlock breaking system, air conditionor control, electronic fuel, injections, entertainment systems
• Industrial system
Robotic machine, control system, smoke detector, fire detector, data collection system, system monitoring, feedback system
• Aerospace
Navigation system, guided system, global positioning system (GPS)
• Communication
Router, network hubs, phone, etc
Some Basic terms:
Chips :
Most digital electronic circuits today are built with semi conductor parts called chips. Chips are purchased from manufacturers specializing in building such parts. Semi-conductor themselves are enclosed in small thin square or rectangle black package made of plastics or ceramics. Each package made of plastics or ceramics. Each package have collection of pins and those pins are response for their own functions. Most digital circuit use just two voltage to do their work
– OVDC somtimes called ground or low input.
– Either 3V or 5V sometimes called VCC or high
The most common mechanism to connect the chips to one another is the printed circuit board.
Gates :
A very simple part built from a handful of semiconductor transistor is called gates or sometime discrete.
or
" A logic gate is an elementary building block of a digital circuit. Most logic gates have two inputs and one output. At any given moment , every terminal is in one of two binary conditions low (0) or high(1)."
# Types of Gates:
And gate:
An AND gate is one whose output is driven to high of both the input are high and in other conditions the output is driven to low
A B Y
0 0 0
0 1 0
1 0 0
1 1 1
OR gate:
An OR gate is one which output is high if either or both of the inputs are high. AND whose output is driven to low if only if both input are low.
A B Y
0 0 0
0 1 1
1 0 1
1 1 1
NOT/ INVERTER gate:
Inverter are the very simple gate i.e output driven to low if the input is high & vice- versa
I/O
1 0
0 1
Bubble:
The bubble or little loop on the invertor symbol is used in other schematic symbols to indicate that an input or an output is inverted that is loop when it should be high & vice versa
A Y
0 0
1 1
X-OR gate:
AN XOR gate is one whose output is driven high if one if the input is high & other input is low. And if both the input are high or low at that conditions the output is low, then it is called XOR gate.
A B Y
0 0 0
0 1 1
1 0 1
1 1 1
NAND gate:
NAND gate is not AND gate.
A B Y
0 0 1
0 1 1
1 0 1
1 1 0
Some Terminology:
Telegraph :
It is one of the example of embedded system that do the long-distance transmission of textual or symbolic (as opposed to verbal or audio) messages without the physical exchange of an object bearing the message. Telegraphy requires that the method used for encoding the message be known to both sender and receiver. Such methods are designed according to the limits of the signaling medium used.
– Telegraph must sort out on the network and provide the clean data stream to the printer.
– Telegraph has to work with a number of different types of a printers without customer configuration.
– Telegraph must respond quite rapidly to certain events.
– Telegraph must keep track of time
Cordless Bar-code scanner
A cordless barcode reader (or barcode scanner) is an embedded system (electronic device) that can read and output printed barcodes to a computer. Like a flatbed scanner, it consists of a light source, a lens and a light sensor translating optical impulses into electrical ones. Additionally, nearly all barcode readers contain decoder circuitry analyzing the barcode's image data provided by the sensor and sending the barcode's content to the scanner's output port.