# Arduino DIY Calculator Using 1602 LCD and 4x4 Keypad

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Hi guys in this instructables we will make a calculator using Arduino which can do basic calculations. So basically we will take input from 4x4 keypad and print the data on 16x2 lcd display and arduino will do the calculations.

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## Step 1: Things You Need

For this instructables we will need following things :

Arduino Uno (Any version will work)

9V Battery

Connecting wires

## Step 2: Connections

The complete circuit diagram of this Arduino Calculator Project is given above. The +5V and ground connection shown in the circuit diagram can be obtained from the 5V and ground pin of the Arduino. The Arduino itself can be powered from your laptop or through the DC jack using a 12V adapter or 9V battery.
We are operating the LCD in 4-bit mode with Arduino so only the last four data bits of the LCD is connected to Arduino. The Keyboard will have 8 output pins which have to be connected from pin 0 to pin 7 as shown above.

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.

## Step 3: Code

/*
*/
#include "LiquidCrystal.h" //Header file for LCD from https://www.arduino.cc/en/Reference/LiquidCrystal
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.
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
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')
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 }

## Step 4: Calculator Output

So we completed the connections & Uploaded the code to arduino and its time to plug power and do some calculations & as you can see i am doing calculations with keypad and you can see the results in the lcd. So have fun making your own diy calculator using arduino.

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