Module V IO Organization and Peripherals IO Devices

Module V I/O Organization and Peripherals

I/O Devices • Peripheral devices refer to any external device connected to the computer. • Computer peripherals can be divided into two categories: – Devices that perform input and output operations: Examples : Keyboard, Mouse, Printer, Video Display, etc – Devices for the secondary storage of data Examples : Magnetic disk, Floppy Disk, CD ROM, etc

Peripheral devices • Peripheral devices to be studied in detail include: – Scanner – Plotter – Joysticks – Touchpad

UQ : Write short note on Scanners

Scanners • Scanners transform printed material and photographs into digital representations. • Most scanners use a flat-bed arrangement, in which the page being scanned is placed over a flat glass surface. • A source of light scans the page, and the reflected light is focused on a linear array of charge coupled devices (CCDs). • When a CCD device is exposed to light, an electrical charge is stored in a tiny capacitor associated with it such that the amount of charge is proportional to the intensity of light. • This charge is collected by appropriate circuitry and converted to a digital representation using an analog to digital converter.

Scanners • For color scanners, red green and blue filters are used to separate the primary colors and process them separately. • As the light source moves across the page, the sensor array is read repeatedly, thus sampling the successive lines of pixels of image. • After scanning the image is represented in memory as an array of pixels.

Scanners

UQ : Write short note on Plotters

Plotters • A plotter is a printer that interprets commands from a computer to make line drawings on paper with one or more automated pens. • The plotter can draw continuous point-to-point lines directly from vector graphics files or commands. • There are different types of plotters: – a drum plotter draws on paper wrapped around a drum which turns to produce one direction of the plot, while the pens move to provide the other direction; – a flatbed plotter draws on paper placed on a flat surface; and – an electrostatic plotter draws on negatively charged paper with positively charged toner.

Plotter

Plotters • Plotters were the first type of printer that could print with color and render graphics and full-size engineering drawings. • Plotters are much more expensive than printers. • They are most frequently used for – CAD (computer-aided design) and – CAM (computer-aided manufacturing). • Hewlett-Packard is the leading vendor of plotters worldwide

UQ : Write short note on Joysticks

Joysticks • Joystick is a short pivoted stick that can be moved by hand to point in any direction in the X-Y plane. • When this information is sent to the computer, the software moves the cursor on the screen in the same direction. • The position of the stick can be sensed by a suitable linear or angular position transducer, such as the potentiometer arrangement. • The voltage outputs of the X and Y potentiometers are fed to two analog-to-digital convertors , whose outputs determine the position of the joystick and thus the desired direction of motion

Joysticks

Joysticks • Joysticks are widely used in video games. • For use in video games, the joystick is shaped into a handle that suits the nature of the game. • It is usually equipped with push buttons to be used for shooting a ball or firing a gun.

Joysticks

UQ : Write short note on Touchpad

Touchpad • The touchpad is a small pad made of pressure sensitive material. • When the user’s finger touches some point on the pad, the pressure causes the electrical characteristics of the material at that spot. • The location of the spot is detected and communicated to the computer.

Touchpad • By moving a finger across the pad, the user can instruct the software to move the cursor on the screen in the same direction. • This makes touchpad a low cost replacement for the mouse, with high degree of robustness and reliability because it contains no moving parts.

Touchpad • The most innovative material for implementing touchpad is the one that has a large number of optical fibers embedded in it. • The material can identify the location of an object touching it as well as the amount of pressure being applied. • This material was developed for robotic applications in space. • A touchpad can be combined with a liquid crystal display to produce a touch sensitive screen that can be used for both input and output operations.

Touchpad