© 2007 the mcgraw-hill companies, inc. all rights reserved input/output chapter 1: part 11

© 2007 The McGraw-Hill Companies, Inc. All rights reserved

Input/OutputChapter 1: Part 11


Overview

• In this chapter, you will learn to

– Explain how to support common input/output ports

– Identify certain common input/output devices on a PC

– Describe how certain specialty input/output devices work on a PC


Supporting Common I/O Ports

CompTIA A+Essentials

Essentials


Serial Ports

• Converts data between serial and parallel devices

• RS-232 Standard– Primary standard used for

serial devices– Rarely used today

Other standards (such as USB) much quicker

• COM ports are serial– 9-pin connector– Used by modems and other devices


Serial Properties

• Speed set in bits per second– 75 bps to 128,0000 bps

• Size of data chunks sent– 7 or 8 bits

• Stop bits– Identify end of chunk

• Flow control


USB Ports

• Understanding USB– Host controller in chipset: contains root hub


USB Speeds

• USB 2.0– Runs at 480 Mbps (Hi-Speed)

• USB 1.1– 1.5 Mbps (Low-Speed) and 12 Mbps (Full-Speed)

• To get Hi-Speed– Hi-Speed device must be plugged into Hi-Speed port

with Hi-Speed cable

• Speed is total speed of bus – Divided between all the devices

• Most systems support both 1.1 and 2.0


USB Hubs and Cables

• USB controller supports up to 127 devices– Won’t find 127 USB ports on any computer– Add hubs to add additional ports

• Hubs can be powered or unpowered

• Cables can’t be longer than 5 meters


USB Configuration

• First rule of USB device installation– Always install driver BEFORE installing device

• UVCView shows controllers and hubs– Microsoft tool—free download


USB

• Device Manager shows all USB devices– Locate USB hub under Universal Serial Bus

Controller icon– Has a Power tab to show power properties

• Beware of sleeping devices– System tells them to sleep to save power– Sleeping devices no longer appear in

Device Manager– Uncheck Allow the computer

to turn off this device to save power


FireWire

• Similar to USB– Different speeds and

different connectors

• IEEE 1394– 1394a runs at 400 Mbps– 1394b runs at 800 Mbps

USB

FireWire


FireWire

• Devices can be connected to a hub or daisy-chained

• Up to 63 devicessupported

• Max cable length can be up to 4.5 meters


General Port Issues

• Basic checks– Is the port bad or the device bad?– Plug in known good device to check port

• If port bad– Check CMOS—turned off?– Check Device Manager—disabled?


General Port Issues

• Check for physical damage– Bent, missing pins– Sometimes possible to reshape pins and plugs


Common I/O Devices


Keyboards

• Primary method of input

• USB keyboards– Make sure USB keyboard support option enabled

in CMOS

• Some settings availablein Keyboard applet


Cleaning the Keyboard

• Clean the top with cloth dampened with water

• Can use isopropyl alcoholfor stubborn dirt


Cleaning the Keyboard

• Cleaning under the keys– Start with compressed air– Can sometimes take the layers apart and clean– Keep track of the location of all keys and parts– Allow sheets to dry before reassembling– Careful when removing keys—can break them


Mice

• Hot keys do exist to work without mouse

• Mouse applet in Control Panel– Slightly different in 2000 and XP– Can adjust buttons and speed of movement


Mice

• Two primary technologies– Ball mice—use small round ball– Optical mice—use LEDs or lasers

• Common problem with ball mice– They get dirty– Mouse pointer becomes jumpy


Cleaning the Mouse

• Remove the ball– Remove dirt from roller

• Optical mouse – Rarely need cleaning– Clean optics when necessary


Scanners

• Enable you to make digital copies of– Photos– Documents– Drawings– And more

• Flatbed scanners– Place document on the glass– Close the lid– Run the software


Scanners

• Software used to capture image

• Default driver:– TWAIN (Technology Without An Interesting Name)

• Common software– Photoshop– Paint Shop Pro– Printer-specific


How to Choose a Scanner

• Consider five primary variables:– Resolution: dots per inch (dpi)– Color depth: bits used for color (8, 16, 24, 36, 48)– Grayscale depth: bits for shades of gray (8, 16, more)– Connection: typically USB or FireWire– Scan speed: seconds

72 dpi 300 dpi 1200 dpi


Installing and Scanning Tips

• Typically USB or FireWire connections– Install drivers before plugging in

• Do the best quality possible first– Then manipulate size and quality for end use

• Two resources affect what you can do:– RAM: 8x10 @ 600 dpi is about 93 MB– Processor speed


Installing and Scanning Tips

• Keep the glass clean– Dirty glass results in dirty scans

• When moving the scanner– Use the locking mechanism for the scanner

light assembly


Digital Cameras

• Storage media—digital film– Secure Digital (SD) card common– About the size of Wheat Thin– Sizes range from 64 MB to 1 GB

• Connection– USB and FireWire common– Allow you to read data

from card while in camera– Card readers allow you to

remove card and pluginto reader


Digital Cameras

• Quality measured in megapixels– 2-megapixel can produce quality 4x6-inch photos– 5-megapixel can produce quality 8x10-inch photos

• Zoom– Optical zoom—physically built into the lens– Digital zoom—software provides zoom capabilities

• Optical zoom more important when comparing camera quality

• Form factor– Larger usually means

better quality


Web Cameras

• Used for Internet interaction

• Biggest issue is image quality– Resolutions between 100,000 to

1.3 million pixels– 1.3 megapixels best quality

achievable with broadband connection

• Frame rate– How many pictures per second– 30 frames per second considered

best


Web Cameras

• Microphones– Some webcams have microphones– Can use your own headset

• Configuring webcams– USB connections common– Install drivers first


Web Cameras

• Configuring software—common steps– Tell the program you want to use a camera– Tell the program whether you want the camera to

turn on automatically when you chat– Configure the image quality– Test the camera


Specialty I/O Devices


Biometric Devices

• Used for authentication– Fingerprints– Retinal scans– Voice recognition


Bar Code Readers

• Designed to read standard Universal Product Code (UPC)

• Frequently used to track inventory– Includes asset inventory– Also used in point-of-sale systems


Touch Screens

• Monitor with sensing device on face

• Detects location of touch– Either by finger or stylus– Responds as if it were a mouse click

• Touch screens can be seen in– Information kiosks– PDAs– Point-of-sale systems– Tablet PCs