Build an Arduino Calculator with 16x2 LCD and Keypad

About this project

At the end of this project you will know how to use a 16x2 LCD and Keypad with Arduino and also how easy it is to program for them using the readily available libraries. You will also understand how to program your Arduino for accomplishing a particular task.

Materials Required:

• Arduino Uno (Any version will work)

• 16×2 LCD Display

• 4×4 Keypad

• 9V Battery

• Breadboard and Connecting wires

D0

1st pin of the keyboard

D1

2nd pin of the keyboard

D2

3rd pin of the keyboard

D3

4th pin of the keyboard

D4

5th pin of the keyboard

D5

6th pin of the keyboard

D6

7th pin of the keyboard

D7

8th pin of the keyboard

D8

Register select pin of LCD (pin 4)

D9

Enable pin of LCD (pin 6)

D10

Data pin 4 (pin 11)

D11

Data pin 4 (pin 11)

D12

Data pin 4 (pin 11)

D13

Data pin 4 (pin 11)

+5V

Connected to Vdd pin of LCD (pin 2)

Ground

Connected to Vss, Vee and RW pin of LCD (pin 1, 3 and 5)

Some Arduino boards might show an error while uploading program if there are anything connected to pin 0 and pin1, so if you experience any just remove the keypad while uploading the program.

Once your connections are done your hardware will look something like this below

Code

• Untitled file

Untitled fileArduino

*
 * 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] = {

  {'7','8','9','D'},

  {'4','5','6','C'},

  {'1','2','3','B'},

  {'*','0','#','A'}

};

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("-CircuitDigest"); //Display a intro message 

   delay(2000); //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
}

Schematics