1

Interfacing User Input DevicesInterfacing User Input Devices

JoysticksJoysticks

TrackballsTrackballs

MousesMouses

Touch ScreenTouch Screen

Light PensLight Pens

X-Y DigitizerX-Y Digitizer

Digital CameraDigital Camera

Chap 0 2

Potentiometer-Type JoysticksPotentiometer-Type Joysticks

Gimbal arrangement Rotates the wipers

when you control the joystick

External and Internal view

Block diagram of IBM game adapter board

Chap 0 3

Potentiometer-Type JoysticksPotentiometer-Type Joysticks

Game adaptor board In expansion slot Address of 201H

Converting resistance into digital value 558 Quad timer

Resistance to Pulse duration

Permit use of two simultaneous joysticks

Duration = 24.2 + 0.011(R) (s)

OUT command to port 201H All four one-shots are

fired IBM PC convert duration

to digital number using clock and register

IN command to port 201H Reads the values of four

one shot output Status of each of the fire

button

Chap 0 4

Potentiometer-Type JoysticksPotentiometer-Type Joysticks Two joystick can

be connected to the IBM PC

IN command returns 1 Byte

information STICK command

in BASIC returns X and Y

coordinates of sticks

Chap 0 5

Build custom designed prototype Build custom designed prototype boardboard

For connecting a potentiometer type and switch type joysticks

Port address = 309H OUT to 309H

/BIOW and /E9 Triggers 556 dual timer

IN at 309H /BIOR and /E9 Pulse duration and Fire

button to be read through 74LS244

Chap 0 6

Build custom designed prototype Build custom designed prototype boardboard

Reading duration BASIC is too slow to read pulse duration

Assembly Language Program is preferred Trigger one shot and then continuously read

the port until both one shot timed out Polling

Use 8253 programmable timer to get more accurate result

Interrupt or Polling See Section 3.3, For more information

Chap 0 7

Alternative Approach Using ADCAlternative Approach Using ADC

ADC0816 on Prototype board For more information,

See Chapter 5

BASIC program to read digital value from each channel

Homework #11-1 Analyze this program

Chap 0 8

Switch Type JoysticksSwitch Type Joysticks

Four switches

Standard 9-Pin

Connect to Prototype board Buffer input values for

all possible switch positions

Two switches can be ON if the stick is moved diagonally

Chap 0 9

Switch Type JoysticksSwitch Type Joysticks

BASIC program Converts joystick’s

switch position into physical movement of cursor

Homework #11-2 Analyze this program

Homework #11-3 Joystick 을 변형하여

DDR 을 구성해보라 .

Chap 0 10

TrackballsTrackballs

Control device Movement of ball

causes optical encoders to generate pulse

Speed Direction of rotation

Most trackball produce 50 ~ 550 pulses per

revolution TTL level signal

x , -x, y, -y The photodiodes in the

optical encoder are placed such that the encoder detect the proper left or right (up and down) movement 1 LED + 1 photodiode :

Speed only 2 LED + 2 photodiode :

Speed and Direction

Chap 0 11

Trackball InterfaceTrackball Interface

Two Up/Down Counter For x and y axes

Boundary Detection Logic Prevent roll over

From 255 to 0 From 0 to 255

Chap 0 12

MousesMouses

Hand-held digital input devices Lisa from Apple

computer 1st computer use

mouse to control applications

Upside down trackball Generate pulses using photo-

optical sensors and optical interrupt disk

IBM PC Interface RS-232C PS-2

Optical Mouse 2 LED inside mouse shine down

onto two-color grid of lines on a special board

Reflect back up through lens and are detected by 4-quadrant sensing device

Similar to Optical Bar Code Reader

Chap 0 13

Touch ScreensTouch Screens Resistive Touch

Screen From TSD Display

Products Output voltage is

proportional to the position touched

5 operating mode Inactive Continuous output Output on Initial touch only ADDS Regent 40

alignment Fixed array of 80 touch

screen

Chap 0 14

Touch ScreensTouch Screens

Using ultrasonic technique Piezoelectric transducer

Mounted along the edge of screen

Set up acoustic surface waves

The travel time of waves are constant unless finger disturb them

The x and y location of finger can be predicted by echo-ranging technique

Using capacitance sensing When a pad is touched

The body’s capacitance is added and sensed

Chap 0 15

HPTouchHPTouch

Adopted in HP 150 PC Optical touch screen

LED Along the bottom and

right side Photodiode

Along the top and left side

40 x 23 matrix of beams The rays are slightly

above the surface of screen

Actually touching screen is not necessary

Softkeys Functions keys

displayed on the bottom of the screen

Computer recognize a selection only when the finger is withdrawn

Chap 0 16

Light PensLight Pens

Raster Scan CRT

Cathode Ray Tube

Sawtooth waveform is applied to yoke

Simplified tracing

Video signal is sent to the Electron Gun

To ensure synchronization of raster scan Trigger pulses are sent

with video signal to mark the beginning of the sawtooth

Hsync for Horizontal Vsync for Vertical

Chap 0 17

Light PensLight Pens

Raster Scan TV

Hsync = 15,750Hz Vsync = 60Hz

IBM Monochrome monitor Hsync = 18,432Hz Vsync = 50Hz

Interlace Mode High resolution graphic

monitor and in TV Allows the image to be

updated twice as often Yet, keeps the BW of

system the same Raster scan is not traveling

twice as fast

Composite video signal Decode by monitor

Chap 0 18

Light PensLight Pens

Detects light emitted by the phosphor screen When tip detects light, it

sends a signal to the processor

Phototransistor is preferred Higher sensitivity Response is slower than

photodiode Produced current from

photo-detector Convert to voltage Amplified High pass filtered

• Remove 60Hz and sunlight

Possible decoding technique for the light pen

counter

counter

Light Pen

Hsync/N

몇 번째Hsync

Hsync/N 중몇 번째

Chap 0 19

X-Y DigitizersX-Y Digitizers

A device that sends to computer the coordinates of the location of a special pen on the tablet

Methods of Conversion Ultrasound

Pen emit ultrasound Sensors in the border of

tablet measure travel time

Location of pen can be calculated

Electromagnetic Tablet set up an

electromagnetic field which is disturbed by the pen in some predictable way

Magnetostrictive Screen like mesh is under

the tablet surface Intersection of two wires

describes an x-y pair Pulses of current travel

along the wire, create magnetic fields

Pen detects moving magnetic filed and determine the coordinates

Chap 0 20

Homework #11-4Homework #11-4

최근 컴퓨터가 소형화 되면서 키보드를 대신할 입력 장치에 대한 관심이 높아지고 있다 . 특히 pen 을 이용하여 직접 입력하는 방법이 문자 인식 기술의 발전에 따라 PDA 등에서 많이 채용되고 있는 추세이다 . 이런 목적을 달성할 수 있는 입력장치를 고안해보라 .