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How to Build DIY Calculator using Arduino Uno, Keypad and character LCD

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Programming is always fun. If you are just starting to use embedded programming, Arduino is a great platform. In this tutorial, we will use Arduino to build our own calculator. These values can be sent via the keyboard (4 x 4 keyboard) and the results can be viewed on the LCD screen (16 x 2 dot matrix). This calculator can perform simple operations such as addition, subtraction, multiplication, and integer division. But once you understand this concept, you can use Arduino’s built-in functions to achieve even scientific functionality.

How to Build DIY Calculator using Arduino Uno

At the end of this project, you will know how to use the 16×2 LCD and keyboard with Arduino and how easy it is to program them using an off-the-shelf library. You will also learn how to program your Arduino to accomplish a specific task.

Hardware required

Wiring       

How to Build DIY Calculator using Arduino Uno

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/*

  • Arduino Keypad calculator Program

*/

#include <LiquidCrystal.h> //Header file for LCD from https://www.arduino.cc/en/Reference/LiquidCrystal

#include <Keypad.h> //Header file for Keypad from https://github.com/Chris–A/Keypad

const byte ROWS = 4; // Four rows

const byte COLS = 4; // Three columns

// Define the Keymap

char keys[ROWS][COLS] = {

{‘1′,’2′,’3′,’A’},

{‘4′,’5′,’6′,’B’},

{‘7′,’8′,’9′,’C’},

{‘*’,’0′,’#’,’D’}

};

byte rowPins[ROWS] = { 0, 1, 2, 3 };// Connect keypad ROW0, ROW1, ROW2 and ROW3 to these Arduino pins.

byte colPins[COLS] = { 4, 5, 6, 7 }; // Connect keypad COL0, COL1 and COL2 to these Arduino pins.

Keypad kpd = Keypad( makeKeymap(keys), rowPins, colPins, ROWS, COLS ); //  Create the Keypad

const int rs = 8, en = 9, d4 = 10, d5 = 11, d6 = 12, d7 = 13; //Pins to which LCD is connected

LiquidCrystal lcd(rs, en, d4, d5, d6, d7);

long Num1,Num2,Number;

char key,action;

boolean result = false;

 

void setup() {

lcd.begin(16, 2); //We are using a 16*2 LCD display

lcd.print(“DIY Calculator”); //Display a intro message

lcd.setCursor(0, 1);   // set the cursor to column 0, line 1

lcd.print(“TechnicalUstaad”); //Display a intro message

delay(5000); //Wait for display to show info

lcd.clear(); //Then clean it

}

void loop() {

 

key = kpd.getKey(); //storing pressed key value in a char

if (key!=NO_KEY)

DetectButtons();

if (result==true)

CalculateResult();

DisplayResult();

}

void DetectButtons()

{

lcd.clear(); //Then clean it

if (key==’*’) //If cancel Button is pressed

{Serial.println (“Button Cancel”); Number=Num1=Num2=0; result=false;}

 

if (key == ‘1’) //If Button 1 is pressed

{Serial.println (“Button 1”);

if (Number==0)

Number=1;

else

Number = (Number*10) + 1; //Pressed twice

}

 

if (key == ‘4’) //If Button 4 is pressed

{Serial.println (“Button 4”);

if (Number==0)

Number=4;

else

Number = (Number*10) + 4; //Pressed twice

}

 

if (key == ‘7’) //If Button 7 is pressed

{Serial.println (“Button 7”);

if (Number==0)

Number=7;

else

Number = (Number*10) + 7; //Pressed twice

}

 

if (key == ‘0’)

{Serial.println (“Button 0”); //Button 0 is Pressed

if (Number==0)

Number=0;

else

Number = (Number*10) + 0; //Pressed twice

}

 

if (key == ‘2’) //Button 2 is Pressed

{Serial.println (“Button 2”);

if (Number==0)

Number=2;

else

Number = (Number*10) + 2; //Pressed twice

}

 

if (key == ‘5’)

{Serial.println (“Button 5”);

if (Number==0)

Number=5;

else

Number = (Number*10) + 5; //Pressed twice

}

 

if (key == ‘8’)

{Serial.println (“Button 8”);

if (Number==0)

Number=8;

else

Number = (Number*10) + 8; //Pressed twice

}

 

if (key == ‘#’)

{Serial.println (“Button Equal”);

Num2=Number;

result = true;

}

 

if (key == ‘3’)

{Serial.println (“Button 3”);

if (Number==0)

Number=3;

else

Number = (Number*10) + 3; //Pressed twice

}

 

if (key == ‘6’)

{Serial.println (“Button 6”);

if (Number==0)

Number=6;

else

Number = (Number*10) + 6; //Pressed twice

}

 

if (key == ‘9’)

{Serial.println (“Button 9”);

if (Number==0)

Number=9;

else

Number = (Number*10) + 9; //Pressed twice

}

if (key == ‘A’ || key == ‘B’ || key == ‘C’ || key == ‘D’) //Detecting Buttons on Column 4

{

Num1 = Number;

Number =0;

if (key == ‘A’)

{Serial.println (“Addition”); action = ‘+’;}

if (key == ‘B’)

{Serial.println (“Subtraction”); action = ‘-‘; }

if (key == ‘C’)

{Serial.println (“Multiplication”); action = ‘*’;}

if (key == ‘D’)

{Serial.println (“Devesion”); action = ‘/’;}

delay(100);

}

 

}

void CalculateResult()

{

if (action==’+’)

Number = Num1+Num2;

if (action==’-‘)

Number = Num1-Num2;

if (action==’*’)

Number = Num1*Num2;

if (action==’/’)

Number = Num1/Num2;

}

void DisplayResult()

{

lcd.setCursor(0, 0);   // set the cursor to column 0, line 1

lcd.print(Num1); lcd.print(action); lcd.print(Num2);

 

if (result==true)

{lcd.print(” =”); lcd.print(Number);} //Display the result

 

lcd.setCursor(0, 1);   // set the cursor to column 0, line 1

lcd.print(Number); //Display the result

}

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