Input/Output Devices

Common and Specialty

Serial Ports

UARTs

• Universal Asynchronous Receiver/Transmitter

• Converts between parallel (bus) and serial

• Connects the computer to a 9-pin, or 25-pin serial port – an RS-232 connector

Terminal Emulation

• “Big Iron” computer systems use terminals and can use computers

• VT100 is old, standard terminal used by lots of equipment (Cisco )

• Terminal Emulation software (once included with modems) about dead but not completely gone

USB• Universal Serial Bus – 4 wires

• USB 1.1 supports 1.5Mbps and 12Mbps

• USB 2.0 supports transfer rates of 480Mbps (about 60MBps) – 25 times faster than parallel ports

• USB 3.0 supports up to 5Gbps

• Far more common than its cousin: IEEE 1394 or Firewire

• 1996 for USB1.0; 2000 for USB 2.0; 2003 for USB 2.0 in laptops

Every device sharesThe USB bus with Every other deviceOn the Host; bus slowsAnd power consumed

Device Manager, Expand USB,Right-click HubProperties

USB issues

• Powered, and unpowered, devices can overload Host Controller

• Three speeds:– Low-Speed (USB 1.1) = 1.5 Mbps– Full-Speed (USB 1.1) = 12 Mbps– Hi-Speed (USB 2.0) = 480 Mbps– SuperSpeed (USB 3.0) = -> 4.8 Gbps

• Hi-Speed is backwards compatible as is SuperSpeed

USB Hubs

• Host Controller supports up to 127 devices

• Use a hub when you run out of ports

• Powered (or not)

• Can daisy-chain up to five hubs

• Allows longer cable runs to devices

• Theory is 5m for longest cable; I have found ~20-foot cables at Fry’s

USB Configuration

• Install the device driver first, then plug in the device

• Windows 2k and XP support keyboards, mice and most flash drives

• Make sure you have the speed the device can run at, otherwise it will default down in speed

• Make sure you have enough power (powered hub(s))

http://www.microsoft.com/whdc/device/stream/vidcap/UVCView.mspx

Firewire• IEEE 1394• Older (by six months) than USB• Digital Video Camcorders and (older) Apple

computers• 6-pin powered connector, or a 4-pin bus-

powered connector • 1394a at 400 Mbps; 1394b at 800 Mbps• Devices can bus master – talk to each other• Maximum of 63 devices• Hubbed or daisy-chained devices• Max cable length is 4.5m

More Firewire

• Can daisy-chain devices (without hubs) if you wish; USB requires hub(s)

• Should install driver first, but most external hard disk drives and Digital Video are supported by Windows

Legacy Free PC

• No serial port(s)

• No parallel port

• No keyboard/mouse ports

• No floppy drive connector

• Thus, no Super I/O chip

Port Issues

• Is it the port, or is it the device?

• Has the CMOS been told to turn off the port? Or Device Manager?

• Is the port broken from too much use?– Bent or broken pins on connector– Bent or broken shell around pins

Somebody got really upset at USB port or device!

Keyboards – 1

• Oldest form of input and still primary form

• If you want to use a USB keyboard, make sure BIOS knows about it (Enable “USB Keyboard Support” somewhere)

Keyboards – 2

• Spills can cook the keyboard controller (Super I/O chip) on motherboard

• Physical damage –rage or a dropped book

• Dirt (and bits of that sandwich)

• I use foaming bathroom cleaner sparingly to clean keyboards

• Need a really good reason to repair a keyboard

Mice

• Windows 98 will grind to a halt if it does not detect a mouse; 2000 and XP won’t

• Windows has drivers for most mouse functions – extra buttons require extra drivers

• Mechanical or ball mouse needs cleaning at points of contact with internal rollers

• Take a tour through Mouse Control Panel applet

Ball Mouse Gunk

Y axisX axis

Spring loaded wheel

Scanners

• Scanners take a PICTURE of the object – you can read the text but computer can not without additional software

• Control of scanner is either at the scanner or software installed on computer – use one or the other but not both at the same time

• TWAIN – Technology Without An Interesting Name

• OCR – Optical Character Recognition• Scan’s file size can quickly get out of hand

Buying a Scanner

• Most people simply go on price – whatever sells for $50-$125. More dollars equals more control over scan parameters.

• Optical resolution – how many data points in an inch. Mine is 9600x4800

• Color depth – how much information can be stored for each data point. 48-bit for me

• Connection – USB now, thank you! Was parallel port

Biometric Devices

• Keep your computer secure• Mostly fingerprint scanning to replace username

and password(s)• Voice recognition – the illusive dream; it is

getting better, but still a long way from accurate• Make it work:

– Install the device– Register your identity with device “train it”– Set what to do when it recognizes you

Barcode Readers

• Used for inventory control – track in and out

• Make sure to use the device the software will understand – forget price

• More USB ports

Touch Screens

• Replaces mouse – uses stylus or finger as replacement for mouse click

• Built-in screens like the one at the checkout counter at Vons, or

• Standalone monitors (HP used to make one)

KVM Switches

• Keyboard, Video and Mouse

• Allows multiple computers and single keyboard/mouse/monitor

• Don’t cross the cables!

Digital Cameras

• Read reviews – MacWorld or a PC magazine or web

• Removable storage media – the “film” usually Secure Digital (SD) cards

• Storage data – measured in megapixels, 3 to 12 megapixels today

• Zoom with camera’s optics not software

Webcams

• Resolution, like cameras, in megapixels – 1.3 per Michael

• Frame rate – pictures per second – up to around 30 per second

• More USB connections

• Configuring webcams – follow the software’s instructions

• Good luck with applications!