Arduino programming

1. Structure

Arduino programs can be divided into three main parts: Structure, Values (variables and constants), and Functions. In this tutorial, we will learn about the Arduino software program, step by step, and how we can write the program without any syntax or compilation error.

Let us start with the Structure. Software structure consists of two main functions −

• Setup( ) function
• Loop( ) function

 Void setup ( ) {  
 }  

• PURPOSE − The setup() function is called when a sketch starts. Use it to initialize the variables, pin modes, start using libraries, etc. The setup function will only run once, after each power-up or reset of the Arduino board.

• INPUT − -

• OUTPUT − -

• RETURN − -

 Void Loop ( ) {  
 }  

• PURPOSE − After creating a setup() function, which initializes and sets the initial values, the loop() function does precisely what its name suggests, and loops consecutively, allowing your program to change and respond. Use it to actively control the Arduino board.

• INPUT − -

• OUTPUT − -

• RETURN − -

2.Variable and Data Types

• int 

Integers are the primary data-type for number storage. int stores a 16-bit (2-byte) value. This yields a range of -32,768 to 32,767 (minimum value of -2^15 and a maximum value of (2^15) - 1).

Example

 int number = 52;  

• Unsigned int

Unsigned ints (unsigned integers) are the same as an int in the way that they store a 2-byte value. Instead of storing negative numbers, however, they only store positive values, yielding a useful range of 0 to 65,535 (2^16) - 1).

Example

 Unsigned int num = 60 ;   

• float

Floating-point numbers can be as large as 3.4028235E+38 and as low as -3.4028235E+38. They are stored as 32 bits (4 bytes) of information.

Example

 float num = 1.352;   

• double

On the Uno and other ATMEGA based boards, Double-precision floating-point number occupies four bytes. That is, the double implementation is exactly the same as the float, with no gain in precision. On the Arduino Due, doubles have 8-byte (64 bit) precision.

Example

 double num = 45.352 ;  

• byte

A byte stores an 8-bit unsigned number, from 0 to 255.

Example

 byte m = 25 ;  

• word

On the Uno and other ATMEGA based boards, a word stores a 16-bit unsigned number. store 0 to 65535  ((2^16)-1)

Example

 word w = 1000 ;  

• short

A short is a 16-bit data-type. On all Arduinos (ATMega and ARM-based), a short stores a 16-bit (2-byte) value. This yields a range of -32,768 to 32,767 (minimum value of -2^15 and a maximum value of (2^15) - 1

Example

 short val = 13 ;  

• long

Long variables are extended size variables for number storage, and store 32 bits (4 bytes), from -2,147,483,648 to 2,147,483,647.

Example

 long velocity = 102346 ;  

• unsigned long

Unsigned long variables are extended size variables for number storage and store 32 bits (4 bytes). Unlike standard longs, unsigned longs will not store negative numbers, making their range from 0 to 4,294,967,295 (2^32 - 1).

Example

 Unsigned long velocity = 101006 ;  

• char

A data type that takes up one byte of memory that stores a character value. Character literals are written in single quotes like this: 'A' and for multiple characters, 

Example

 Char chr_a = ‘a’ ; 

 Char  chr_a = 65 ; 

• String 

strings use double quotes: "ABC".

Example

 String value = "Welcome to Arduino programing"  

3.Function Digital I/O

• pinMode

Description

Configures the specified pin to behave either as an input or an output. See the Digital Pins page for details on the functionality of the pins.

As of Arduino 1.0.1, it is possible to enable the internal pullup resistors with the mode INPUT_PULLUP. Additionally, the INPUT mode explicitly disables the internal pullups.

Syntax
pinMode(pin, mode)

Parameters

pin: the Arduino pin number to set the mode of.
mode: INPUT, OUTPUT, or INPUT_PULLUP. See the Digital Pins page for a more complete description of the functionality.

Example Code

The code makes the digital pin 13 OUTPUT and Toggles it HIGH and LOW

void setup() {
  pinMode(13, OUTPUT);    // sets the digital pin 13 as output
}

void loop() {
  digitalWrite(13, HIGH); // sets the digital pin 13 on
  delay(1000);            // waits for a second
  digitalWrite(13, LOW);  // sets the digital pin 13 off
  delay(1000);            // waits for a second
}

• digitalWrite()

Description

Write a HIGH or a LOW value to a digital pin.

If the pin has been configured as an OUTPUT with pinMode(), its voltage will be set to the corresponding value: 5V (or 3.3V on 3.3V boards) for HIGH, 0V (ground) for LOW.

If the pin is configured as an INPUT, digitalWrite() will enable (HIGH) or disable (LOW) the internal pullup on the input pin. It is recommended to set the pinMode() to INPUT_PULLUP to enable the internal pull-up resistor. See the Digital Pins tutorial for more information.

If you do not set the pinMode() to OUTPUT, and connect an LED to a pin, when calling digitalWrite(HIGH), the LED may appear dim. Without explicitly setting pinMode(), digitalWrite() will have enabled the internal pull-up resistor, which acts like a large current-limiting resistor.

Syntax

digitalWrite(pin, value)

Parameters

pin: the Arduino pin number.
value: HIGH or LOW.

•   delay()

Description

Pauses the program for the amount of time (in milliseconds) specified as parameter. (There are 1000 milliseconds in a second.)

Syntax
delay(ms)

Parameters

ms: the number of milliseconds to pause. Allowed data types: unsigned long.

Example Code

The code pauses the program for one second before toggling the output pin.

int ledPin = 13;              // LED connected to digital pin 13

void setup() {
  pinMode(ledPin, OUTPUT);    // sets the digital pin as output
}

void loop() {
  digitalWrite(ledPin, HIGH); // sets the LED on
  delay(1000);                // waits for a second
  digitalWrite(ledPin, LOW);  // sets the LED off
  delay(1000);                // waits for a second
}

Circuit 

• digitalRead()

Description

Reads the value from a specified digital pin, either HIGH or LOW.

Syntax

digitalRead(pin)

Parameters

pin: the Arduino pin number you want to read

Returns

HIGH or LOW

Example Code

Sets pin 13 to the same value as pin 7, declared as an input.

int ledPin = 13;  // LED connected to digital pin 13
int inPin = 7;    // pushbutton connected to digital pin 7
int val = 0;      // variable to store the read value

void setup() {
  pinMode(ledPin, OUTPUT);  // sets the digital pin 13 as output
  pinMode(inPin, INPUT);    // sets the digital pin 7 as input
}

void loop() {
  val = digitalRead(inPin);   // read the input pin
  digitalWrite(ledPin, val);  // sets the LED to the button's value
}

Circuit 

4.Serial Monitor

Serial.begin()

Description

Sets the data rate in bits per second (baud) for serial data transmission. For communicating with Serial Monitor, make sure to use one of the baud rates listed in the menu at the bottom right corner of its screen. You can, however, specify other rates - for example, to communicate over pins 0 and 1 with a component that requires a particular baud rate.

An optional second argument configures the data, parity, and stop bits. The default is 8 data bits, no parity, one stop bit.

Syntax

Serial.begin(speed)

Example Code

 void setup() {  
  Serial.begin(9600);  
 }  
 void loop() {  
  Serial.println("Welcome to Bangladesh");  
  delay(1000);  
 }  

Serial.read()

Description

Reads incoming serial data.

Serial.read() inherits from the Stream utility class.

Syntax

Serial.read()

Example Code

char input;
 
void setup() {
    Serial.begin(9600); 
    delay(2000);  
 
    Serial.println("Type something!");
}
 
void loop() {
    if(Serial.available()>0){
        input = Serial.read();
        Serial.print("You typed: " );
        Serial.println(input);

    }
}

Serial.print()

Description

Prints data to the serial port as human-readable ASCII text. This command can take many forms. Numbers are printed using an ASCII character for each digit. Floats are similarly printed as ASCII digits, defaulting to two decimal places. Bytes are sent as a single character. Characters and strings are sent as is. For example-

• Serial.print(78) gives "78"
  

• Serial.print(1.23456) gives "1.23"
  

• Serial.print('N') gives "N"
  

• Serial.print("Hello world.") gives "Hello world."

Syntax

Serial.print(val)

Serial.print(val, format)




Serial.available()

Description

Get the number of bytes (characters) available for reading from the serial port. This is data that’s already arrived and stored in the serial receive buffer (which holds 64 bytes).

Serial.available() inherits from the Stream utility class.

Syntax

Serial.available()




5.Function Analog I/O 

analogRead()

[Analog I/O]

Description

Reads the value from the specified analog pin. Arduino boards contain a multichannel, 10-bit analog to digital converter. This means that it will map input voltages between 0 and the operating voltage(5V or 3.3V) into integer values between 0 and 1023. On an Arduino UNO, for example, this yields a resolution between readings of: 5 volts / 1024 units or, 0.0049 volts (4.9 mV) per unit. See the table below for the usable pins, operating voltage and maximum resolution for some Arduino boards.

The input range can be changed using analogReference(), while the resolution can be changed (only for Zero, Due and MKR boards) using analogReadResolution().

On ATmega based boards (UNO, Nano, Mini, Mega), it takes about 100 microseconds (0.0001 s) to read an analog input, so the maximum reading rate is about 10,000 times a second.

BOARD	OPERATING VOLTAGE	USABLE PINS	MAX RESOLUTION
Uno	5 Volts	A0 to A5	10 bits
Mini, Nano	5 Volts	A0 to A7	10 bits

Syntax

analogRead(pin)

Parameters

pin: the name of the analog input pin to read from (A0 to A5 on most boards, A0 to A6 on MKR boards, A0 to A7 on the Mini and Nano, A0 to A15 on the Mega).

Returns

The analog reading on the pin. Although it is limited to the resolution of the analog to digital converter (0-1023 for 10 bits or 0-4095 for 12 bits). Data type: int.

Example Code

The code reads the voltage on analogPin and displays it.

 int analogPin = A3; // potentiometer wiper (middle terminal)  
            // connected to analog pin 3  
           // outside leads to ground and +5V  
 int val = 0; // variable to store the value read  
 void setup() {  
  Serial.begin(9600);      // setup serial  
 }  
 void loop() {  
  val = analogRead(analogPin); // read the input pin  
  delay(1000);  
  Serial.println(val);     // debug value  
 }   

Circuit 

analogWrite()

[Analog I/O]

Description

Writes an analog value (PWM wave) to a pin. Can be used to light a LED at varying brightnesses or drive a motor at various speeds. After a call to analogWrite(), the pin will generate a steady rectangular wave of the specified duty cycle until the next call to analogWrite() (or a call to digitalRead() or digitalWrite()) on the same pin.

BOARD	PWM PINS	PWM FREQUENCY
Uno, Nano, Mini	3, 5, 6, 9, 10, 11	490 Hz (pins 5 and 6: 980 Hz)

Syntax

analogWrite(pin, value)

Parameters

pin: the Arduino pin to write to. Allowed data types: int.
value: the duty cycle: between 0 (always off) and 255 (always on). Allowed data types: int.

Example Code

Sets the output to the LED proportional to the value read from the potentiometer.

 int ledPin = 9;   // LED connected to digital pin 9  
 int val = 90;     // variable to store the read value  
 void setup() {  
  pinMode(ledPin, OUTPUT); // sets the pin as output  
 }  
 void loop() {  
  analogWrite(ledPin, val/4); // analogRead values go from   
                       //analogWrite values from 0 to 255  
 }  

Circuit 

6. Light Brithnase control

Circuit 

Code

 int ledPin = 6;   // LED connected to digital pin 6  
 int analogPin = A3;  // potentiometer connected to analog pin 3  
 int val = 0;     // variable to store the read value  
 void setup()  
 {  
  pinMode(ledPin, OUTPUT);  // sets the pin as output  
 }  
 void loop()  
 {  
  val = analogRead(analogPin);  // read the input pin  
  analogWrite(ledPin, val / 4); // analogRead values go from 0 to 1023,analogWrite values from 0 to 255  
 }