Lab7: Introduction

to Arduino
ENGG1100 Engineering Design I
 Study this document before coming to the lab
 Demonstrate your results of the following
exercises to a TA before the lab ends.
 Part (b) of Exercise 7.1 (page 28)
 Part (b) of Exercise 7.2 (page 33)
 Exercise 7.3 (page 41)
 Exercise 7.4d (page 52)

This material is based on various resources

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Overview
• Theory
• Introduction to Arduino
• Hardware system structure
• Programming structure
• Practice
• Experiment1: LED control
• Experiment1: Input/output functions
• Experiment2: Pulse width modulation (PWM)
• Experiment3: Finite State machines (FSM)

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Introduction to Arduino
• Arduino is a computation tool for sensing and
controlling signals
• It is more convenient and cost effective than using
a personal computer PC.
• It's an open-source system in terms of hardware
and software.
• You can download the Integrated Development
Environment (IDE) for your own OS from http://
arduino.cc/en/Main/Software
• Follow the instruction to install the IDE
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Arduino UNO
• Microcontroller is based on 14 digital input/output (I/O) pins
13,12,… ………2,1,0
ATmega328
• If needed , download Arduino Integrated
D
evelopment Environment IDE http://ardui
no.cc/en/Main/Software#toc1

• 14 digital input/output (I/O)

pins plus
A0-A5
• 6 analog input pins (these 6 Analog inputs, they can also
pins can also be programmed be used as digital I/O pins
to be digital I/O pins)
• A 16 MHz ceramic resonator

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the Arduino
IDE
• To start Arduino IDE,
click Start Menu  All
Programs  Arduino

• Make sure the board

model (Arduino Uno)
and connected port
(depends on your PC)
are correct
Your board Model The port that your
board connected to
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Select Board

Select a correct board

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Select Port

Select a correct port.

The actual number
depends on your
system.

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Arduino IDE
Tool Bar Serial monitor,
Can use this to issue
commands to the
board, and read
outputs from the
board.
This programming Area
is called “Sketch”.

The program code are placed here.

Status Message

Messages from the system

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Toolbar
• Verify
• Checks code for errors
• Upload
• Compiles and uploads code to the Arduino I/O board
• New
• Creates a new sketch
• Open
• Open sketch
• Save
• Save sketch
• Serial Monitor
• Display serial data being sent from the Arduino board
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Arduino Code
To run a program in Arduino, your sketch should
contain two methods
void setup()
{
// initialization of variables, pin modes, libraries
// run once after each power up or reset
}

void loop()
{
// loops the content consecutively
// allowing the program to change and respond
}

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Basic software functions

• Hardware related
• pinMode(), setup the functions of hardware pins
• digitalWrite(), set a pin to a digital level : ‘1’ or ‘0’
• digitalRead(), read the digital level of a pin: ‘1’ or ‘0’
• delay()
• Software related
• If-then-else
• For
• Switch-case

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System setup procedures

• (Step 1) Setup the direction of the pins:
• using pinMode(),
• (Step 2) Then you can set a pin to : HIGH or LOW
• (Step 2a) digitalWrite(), //set pin to : HIGH ‘1’ or LOW ‘0’
• or
• (step 2b) digitalRead(), //read state of pin: HIGH ‘1’ or
LOW ‘0’

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Basic Function (step1) –

pinMode()
• pinMode() is used to configure the specified pin to
behave either as an input or output, or input_pullup
• Syntax Pin =0,..,13, or A0,A1,..,A5
Write comment for you to read
for Digital I/O, or
pinMode(pin, mode) // comment
• pin: the index number of the pin whose mode you wish to set
• mode: INPUT, OUTPUT, INPUT_PULLUP
• Example:
• pinMode(1, OUTPUT)//setup pin1 =digital out
• pinMode(3, INPUT)//setup pin3 =digital in
• pinMode(A3, INPUT)//setup A3 for digital in
• pinMode(A3, OUTPUT)//setup A3 for digital out
• If no PinMode applied to A0->A5, they are analog_in
by default.
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Meaning of INPUT,
OUTPUT, INPUT_PULLUP
HIGH(5V) or LOW(0V)
• INPUT: Arduino

• OUTPUT:
HIGH(5V) or LOW (0V) Arduino

High(5V))
• INPUT_PULLUP:
1KΩ
When the pin is not Arduino
connect to HIGH(5V) or LOW)
or
anything, it is HIGH not_connected_to_anything

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Basic Function(step2a) –
digitalWrite()
• digitalWrite() is used to write a HIGH or a LOW
value to a digital pin

• Syntax
digitalWrite(pin, value) // comment
• pin: the number of the pin whose value you wish to set
• value: HIGH (5 V) or LOW (Ground)
• Example:
• digitalWrite(pin, value) // comment
• E.g
• digitalWrite(1, HIGH)//set pin1 to HIGH
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Basic Function(step2b) –
digitalRead()
• digitalWrite() is used to read the value from a
specified digital pin, either HIGH or LOW

• Syntax
digitalRead(pin)
• pin: the number of the pin whose mode you want to
read (integer)
• Example:
• digitalRead(pin)// read the state of the
• // it can be “HIGH” or
“LOW”

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Some other basic Function –

delay()
• delay() is used to pause the program for the
amount of time (in milliseconds)

• Syntax
delay(ms)
• ms: the number of milliseconds to pause (unsigned long)

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Basic Control Structure – IF

• Syntax
IF(condition1){
// do stuff if condition1 is true
}ELSE IF (condition2){
// do stuff only if condition1 is false
// and conition2 is true
}ELSE{
// do stuff when both condition1 and
// condition2 are false
}

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Basic Control Structure –

FOR
• Syntax
FOR(initialization; condition; increment){
// statement(s);
}

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Basic Control Structure

– SWITCH-CASE
• switch (var) {
• case label1:
• // statements when var=label1
• break;
• case label2:
• // statements when var=label2
• break;
• default:
• // statements
•}
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More Functions
• Please visit http://arduino.cc/en/Reference/ for
Arduino Language Reference

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Experiment 7.1:
Blinks an LED
Turns on/off an Active-LOW LED

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Start Arduino IDE

• Stack the debug board on
the Arduino board, connect
it to the PC via a USB cable
and start the Arduino IDE
• To start Arduino IDE, This area is called the “Sketch”
click Start Menu  All
Programs  Arduino
• Make sure
• ToolsboardArduino
Uno
• Tools serial port  com?
(choose a correct one) Your board Model The port that your
board connected to
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Connect Arduino UNO to
PC 14 digital input/output (I/O) pins
13,12,… ………2,1,0
Success
Connection:
Connect to LED will be
PC through ON
USB Cable

24

6 Analog inputs (or Digital I/O)

A5A0 24
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Can be used as digital I/O too
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File/Load the Code to Arduino(or cut

and paste to the “sketch” area)
• Click verify to check whether your code is correct.
After verification, you can upload the code to the
Arduino board

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Circuit and Code

• Cut and paste the code below to the sketch area of
the Arduino IDE , and click on
• demo71a.ino
//demo71a.ino
int led = 7; // assign a name to pin 7
// This setup routine runs once when reset is pressed
void setup () {
pinMode (led, OUTPUT); // assign the pin as an output
}
// This loop routine runs over and over again forever
void loop() {
digitalWrite (led, HIGH); // turn off the LED
delay (3000); // wait for three second
digitalWrite (led, LOW); // turn on the LED
delay (1000); // wait for a second
}
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Result of the program

• LED 7 should be blinking

LED7 is ON for
a second and
OFF for three
second

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Exercise 7.1
a) Write a program to turn on and off each of the
LEDs (LED0,… LED7) one at a time. Such that,
LED0 is turn on for a second and off for one
second, then it will be the turn for LED1 and so
on till LED7 is selected. After that, start again with
LED0.
b) Why all LEDs light up at the beginning? Change
your program to solve this problem?
Advanced exercise (to be done in your spare time if
you are interested): Display the state of the LED using
the serial monitor. See
http://arduino.cc/en/Serial/Print#.UxFaulPYFCs
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Hints X start value Test for

X stop condition
X increment (use x++) or
decrement (use x--)
• //setup pinMode
• void setup() {
• for (int x=0; x<8; x++)
• {
• pinMode(x, OUTPUT);
• }
• }

• void loop() {
• //to be filled by students

• }
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Experiment 7.2:
Get Input
Use an input value to control an LED

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Use an integer variable “InputPin” to hold the pin number: 2

demo72.inoUse an integer variable “ledPin” to hold the led number: 7
//demo72.ino
int inputPin = 2; // the number of the input pin
int ledPin = 7; // the number of the LED pin
int inputState = 0; //variable for reading the input status
void setup () {
pinMode (ledPin, OUTPUT); //assign the pin as an output
pinMode (inputPin, INPUT); //assign the pin as an input
}

void loop() {
inputState = digitalRead(inputPin); //get status
if (inputState == LOW) { // GND is connected
digitalWrite(ledPin, HIGH); // turn off LED
}
else {
digitalWrite(ledPin, LOW); //turn on LED
}
}
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 demo (7.2) Expected
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Results (verify this using

your setup)
5 V is connected to Pin 2 GND is connected to Pin 2
LED7 is ON LED2 is OFF LED7 is OFF LED2 is ON
To show the To show the
output input

Input/output
13 12 11 10 9 8 7 6 5 4 3 2 1 0

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Exercise 7.2
a) Explain what you see after running demo72.ino
b) Modify the code so that the input pin is 3 (instead
of 2) and output LED is 6 (instead of 7). Run the
code to verify your result.
Advanced exercise (to be done in your spare time if
you are interested): Use the keyboard of your PC to
control the on and off of the LEDS. See
http://arduino.cc/en/Serial/read#.UxFdTPmSxIE

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Experiment 7.3:
Pulse Width
Modulation (PWM)
Use PWM to control the intensity an LED

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Pulse Width Modulation

(PWM)
• PWM is a modulation technique that obtains
analog results by digital means
• The duration of “ON” is called the pulse_width
• Create an analog output by changing the pulse_width
for a fixed frequency signal
• Can be used to control the speed of a motor
• The longer the switch is ON compared to the OFF
periods, the higher the power supplied to the load
• Advantage: easy to use and implement, low power
loss.
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PWM in Arduino
• The green lines represents
a regular time period i.e.
inverse of PWM frequency
• Arduino’s default PWM
frequency is approximately
500 Hz i.e. a period is 2 ms
• Use analogWrite() to
control the pulse width
• Varying LED’s brightness
• Varying motor’s speed
• Only pin 3, 5, 6, 9, 10, and
11 can be used for PWM Courtesy of Arduino.cc

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Arduino PWM pins

Only pins
• 3, 5, 6, 9, 10,
and 11 can
be used for
PWM

PWM outputs
13 12 11 10 9 8 7 6 5 4 3 2 1 0

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analogRead()
• analogRead() is used to read the value from the
specified analog pin
• The input voltage between 0 V and 5 V will be mapped
into integer values between 0 and 1023 i.e. 4.9 mV/unit

• Syntax
return = analogRead(pin)
• pin: the number of the analog input pin to read from 0 V
to 5 V
• return: integer from 0 to 1023

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analogWrite()
• analogWrite() is used to set the duty cycle of a
PWM pulse
• After a call to analogWrite(), the pin will generate a
steady square wave of the specified duty cycle until the
next call to analogWrite(), digitalRead() or digitalWrite()
on the same pin
• Syntax
analogWrite(pin, value)
• pin: the pin to write to
• value: the duty cycle between 0 (always OFF) and 255
(always ON)

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Run this Demo73.ino and

explain what you see
//demo73.ino
int ledPin = 3; // must be one of 3, 5, 6, 9, 10, or 11 for PWM
void setup () {
pinMode (ledPin, OUTPUT); // assign the pin as an output
}

void loop() {
int dtwait = 1000;
analogWrite (ledPin, 255-0); //LED OFF,when value=255,LED=off
delay (dtwait);
analogWrite (ledPin, 255-100); // a dimmer LED
delay (dtwait);
analogWrite (ledPin, 255-255); // full bright LED, when value=0
delay (dtwait);
}

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Exercise 7.3
• Write the program to control the intensity of LED5
continuously and repeatedly from dark to full and
dark again within a period of five seconds.
• Hint: Change intensity every 0.5 seconds, put the
statements inside: Void Loop( ) { Your code }
• Advanced exercise (to be done in your spare time if
you are interested): Use the 7 LEDS as an intensity
ramp: intensity changes from low to high for LED0
to LED7 at the beginning and then gradually reverse
the pattern continuously and repeatedly at 1Hz.
(Hints: may need to use for())
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Experiment 7.4:
Finite State
Machine (FSM)
Use FSM to control a system

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Logic Control
• Logic control is an essential part to develop an
intelligence device

• Logic control can be developed by

• Truth table
• You only need to know the corresponding input/output relation
• As there is no memory, only simple operations can be achieved
• Finite State Machine
• Decision is based on what it has done i.e. the system has
memory, the performance can be more complex

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A FSM demo74a.ino
(FSM with no input)
Transition condition:
• delay 1 second

start State: State:

State 1 State 2

Entry action: Entry action:

LED3 is OFF LED3 is ON
LED4 is ON LED4 is OFF

Transition condition:
delay 2 seconds

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//demo74a.ino •

•
void loop() {

switch(state) {

Try this code •

•
case STATE1:

digitalWrite(3, HIGH); // LED OFF

• digitalWrite(4, LOW); // LED OFF

• //demo74a.ino • delay(1000);

•
• #define STATE1 1 state=STATE2;

• break;
• #define STATE2 2 • case STATE2:

• #define STATE_END 100 • digitalWrite(3, LOW); // LED ON

• digitalWrite(4, HIGH); // LED OFF

• unsigned char state=1;
• delay(2000);
//init. to state1
• state=STATE1;
• void setup() { • break;

• pinMode (3, OUTPUT); • case STATE_END: // turn off the LEDs, this state is
not used here

• pinMode (4, OUTPUT); • digitalWrite(3, HIGH); // LED OFF

• digitalWrite(4, HIGH); // LED OFF

• }
• break;

• default:

• state=STATE_END;

• break;

• } }

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Demo 7.4b:
Two-State FSM with input
• When a magnetic strip is detected, the LED is ON
• When there is no magnetic strip, the LED is OFF
State Transition Table State Diagram
Input Current State Next State
Magnetic strip is ON ON
detected
Magnetic strip is OFF ON
detected
No magnetic strip ON OFF
is detected
No magnetic strip OFF OFF
is detected

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Two-State FSM demo7.4b

• Circuit
• Connect one leg of a magnetic sensor to GND and
another leg to pin 7
• Code demo74b.ino
• When a magnet is near the magnetic switch sensor (if
you don’t have a magnetic switch, connect Pin7 to
ground to simulate the effect), then
LED5=ON,LED6=OFF
• When a magnet is NOT near the magnetic switch sensor
(or leave pin7 unconnected), then LED5=OFF,LED6=ON
• Try demo74b.ino

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• void loop() {
• //demo74b.ino • switch(state) {
• #define STATE1 1 • case STATE1:

• #define STATE2 2 • digitalWrite(ledPin_S1, HIGH); // LED OFF

• digitalWrite(ledPin_S2, LOW); // LED ON

• #define STATE_END 100
• if (digitalRead(magnetic) == LOW)
• int magnetic = 7; • state=STATE2; break;

• int ledPin_S1 = 5; • case STATE2:

• digitalWrite(ledPin_S1, LOW); // LED ON

• int ledPin_S2 = 6;
• digitalWrite(ledPin_S2, HIGH); // LED OFF
• unsigned char state=1; • if (digitalRead(magnetic) == HIGH)

• void setup() { • state=STATE1; break;

• case STATE_END:
• pinMode (magnetic, INPUT);
• digitalWrite(ledPin_S1, HIGH); // LEDOFF
• pinMode (ledPin_S1, • digitalWrite(ledPin_S2, HIGH); // LED OFF
OUTPUT); pinMode break;
(ledPin_S2, OUTPUT); • default:

• } • state=STATE_END;

• break; }}

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Exercise 7.4c
• Write a FSM program that controls two LEDs
through two input signals, the specification is
shown in flow diagram 7.4c in the next slide
• Use inputs
• pin0 for sensor1, and
• pin1 for sensor2.
• The values of input signals (sensor 1 and sensor 2) can be
either GND (LOW) or 5V (HIGH)
• Use outputs
• pin5 for LED1 and
• pin6 for LED2

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Exercise 7.4c
State Diagram 7.4c

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Hints
• //hint for ans74.c
• void loop() {
• #define STATE1 1
• switch(state) {
• #define STATE2 2
• case STATE1:
• #define STATE3 3
• digitalWrite(led1, LOW);
• #define STATE4 4
• digitalWrite(led2, LOW);
• #define STATE_END 100
• if ((digitalRead(sensor1) == LOW) &&
(digitalRead(sensor2) == HIGH)) state=STATE2;
• int sensor1 = 0; • else if ((digitalRead(sensor1) == HIGH) &&
• int sensor2 = 1; (digitalRead(sensor2) == LOW)) state=STATE3;

• int led1 = 5; • else if ((digitalRead(sensor1) == HIGH) &&

(digitalRead(sensor2) == HIGH)) state=STATE4;
• int led2 = 6;
• break;
• unsigned char state=4;
• // …………To be filled in by students
• void setup() {
• pinMode (sensor1, INPUT);
• pinMode (sensor2, INPUT);
• pinMode (led1, OUTPUT);
• pinMode (led2, OUTPUT);
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Exercise 7.4d
• Improve the previous exercise with the following
conditions
• When both LEDs are ON, they should be in full
brightness
• When either LED is lighted up, the brightness of that LED
should be as low as 10 %
• Hint use: analogWrite(led1, 255-25); //will give 10% LED light

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Summary
• Learned the use of
• the Arduino microcontroller
• digital input / outputs functions
• some basic functions
• if-then-else and switch-case control statements in
programs
• Finite state machines

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