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Event-Driven Programming andSensor Programming

Yinong Chen

Introduction to Engineering Using Robotics Laboratories

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Table of Contents

Event-Driven Sensor Programming2

Types of Sensors3

Program a Range Sensor4

Control Flow vs. Event-Driven1

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Ro

uti

ne

of

aM

edic

al

Pro

fess

or

inC

on

tro

lF

low

Mo

de

Research

Write proposal

Consult students

Teaching Prep

See ICU patients

See out-patients

Teach a course

Read reports

See all in-patients

See ICU patients

Outside officeIn Office

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Ro

uti

ne

of

Med

ica

lP

rofe

sso

rsin

Ev

ent-

Dri

ve

Mo

de

Research

Write proposal

Student questions

Teaching Prep

Answer studentquestions

ICU patient

Teach a course

See out-patients

Read reports

See all in-patients

Outside office

EventBoard

AlertBoard

ICU patient

ICU patient

Student questions

Student questions

Student questions

Student questions

Not

ific

atio

n

Inte

rrup

t/

Not

ific

atio

n

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Event-Driven Programming

Event-driven programming is a computingparadigm which allows interaction between thecomputer program and the user;

The execution flow of the program isdetermined by• user actions, such as mouse clicks, key presses,

sensor outputs (e.g., touch sensor), and

• messages from other programs

It assumes that there are unlimited number ofprocessors available, and the events can behandled immediately.

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Sensors and Actuatorsin Robotics Application

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Eventemitter

Motorposition

M1Notify

handler M1

Motor 1control

Motor1

Eventemitter

T1

T2

Tm

Notify handler T1

Notify handler T2

Notify handler Tm

TouchSensor

Main programin a loop

HandlerTouch

HandlerSonar

Eventemitter

S1

S2

Sn

Notify handler S1

Notify handler S2

Notify handler Sn

SonarSensor

HandlerMotor 1

HandlerMotor 2

Eventemitter

Motorposition

Motor 2control

Motor2

Notifyhandler M2

M2

Frequency ofreading

Alert

LightSonar

Frequency ofreading

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Communication betweenActivities / Services in VPL

Event!

Activity /Service

Activity /Diagram

0 0 0 0

1 1 1 1

Data

Signals

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Variable and Data Flow

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Data Output versus Notification Output

Control Flow

Queue

Set

Event Driven:All will be done atthe same time, but

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Types of Sensors

Ranging sensors, such as

sonar,

ultrasonic,

IR, and

laser sensors:

These sensors return the distance tothe object.

They typically have two lens (eyes).One sends out a light beam and theother receives the reflected beam.

By measuring the time and angle ofreflected beam, as shown in theFigure on the right, the sensors canmeasure the distance to the object

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Types of SensorsThere are many types of sensors

Contact (touch) sensor: A signal isgenerated when touched

Compass (magnetic) sensor

GPS (Global Positioning System)

Color sensor: return different valuefor different colors

Temperature sensorReturn the temperature

Vehicle accelerometer sensor

Vehicle tire pressure sensor

…

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EV3 and Edison Robots

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Example: NXT Robot and An Application

SonarSensor

TouchSensor

Actuator:Motor Effector:

Finger

While (true){

if touch sensor value == 1Trigger the motor;

elseif sonar distance < 3 feet{

while sonar distance < 5{}Trigger the motor;

}}

Image from: http://www.gadgetsireland.tv/2007/09/

This program will not be workingwithout event-driven programming:Touch sensor has no chance!

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Test Sensors in ASU-VPL

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A Line-Follower Program Using Color Sensor