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Bernd Desens

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Description

MyCalculator

I created a small math calculator to do some quick calculations. It works through a display that displays the data inputs from the keypad and the outputs calculated by the program. The calculator can do addition, subtraction, multiplication and division.

Code

Internal Code

C/C++

#include <Keypad.h>
#include <Wire.h> 
#include <LiquidCrystal.h>

LiquidCrystal lcd(13, 12, 11, 10, 9, 8);

long firstNum = 0;
long secondNum = 0;
double total = 0;

char customKey;
const byte ROWS = 4;
const byte COLS = 4;

//create a table in code
char keys[ROWS][COLS] = {
  {'1','2','3','+'},{'4','5','6','-'},{'7','8','9','*'},{'C','0','=','/'}
};

//connect rows to tab
byte rowPins[ROWS] = {7,6,5,4};

//connect columns to the board
byte colPins[COLS] = {3,2,1,0}; 


//instance of the NewKeypad class
Keypad customKeypad = Keypad( makeKeymap(keys), rowPins, colPins, ROWS, COLS); 

void setup()
{
lcd.begin(16, 2); //create despla
for(int i=0;i<=3;i++);
lcd.setCursor(0,5);
  lcd.print("Calculator");
delay(2000);
lcd.clear();

//explain the table
lcd.setCursor(0, 0);
  lcd.print("A -> +");
lcd.setCursor(9, 0);  
  lcd.print("B -> -");
lcd.setCursor(0, 5);
  lcd.print("C -> *");
lcd.setCursor(9, 5);
  lcd.print("D -> /");
delay(3000);
  
lcd.clear();
  
lcd.setCursor(0, 0);
  lcd.print("# -> =");
lcd.setCursor(0, 5);
  lcd.print("* -> Clear");
delay(3000);
  
lcd.clear();
}


void loop()
{

  customKey = customKeypad.getKey();
  switch(customKey) 
  {
  case '0' ... '9': 
    lcd.setCursor(0,0);
    firstNum = firstNum * 10 + (customKey - '0');
    lcd.print(firstNum);
    break;

  case '+':
    if (total != 0)firstNum = total; //ipnut first number
    lcd.setCursor(0,1);
    lcd.print("+"); //print sign
    secondNum = SecondInput();
    total = firstNum + secondNum; //calculate
    lcd.setCursor(0,3);
    lcd.clear();
    lcd.print(total); //print result
    firstNum = 0, secondNum = 0; //set the first and second numbers zero for a successive calculation
    break;

  case '-':
    if (total != 0)firstNum = total;
    lcd.setCursor(0,1);
    lcd.print("-");
    secondNum = SecondInput();
    total = firstNum - secondNum;
    lcd.setCursor(0,3);
    lcd.clear();
    lcd.print(total);
    firstNum = 0, secondNum = 0;
    break;

  case '*':
    if (total != 0)firstNum = total;
    lcd.setCursor(0,1);
    lcd.print("*");
    secondNum = SecondInput();
    total = firstNum * secondNum;
    lcd.setCursor(0,3);
    lcd.clear();
    lcd.print(total);
    firstNum = 0, secondNum = 0;
    break;

  case '/':
    if (total != 0)firstNum = total;
    lcd.setCursor(0,1);
    lcd.print("/");
    secondNum = SecondInput();
    lcd.setCursor(0,3);
    
	lcd.clear();
    if (secondNum == 0){
      lcd.print("Invalid");
    }else{
        total = (float)firstNum / (float)secondNum;
      }

    lcd.print(total);
    firstNum = 0, secondNum = 0;
    break;

  case 'C':
    total = 0;
    lcd.clear();
    lcd.print("0.00");
    break;
  }
}

long SecondInput()
{
  while( 1 )
  {
    customKey = customKeypad.getKey();
    if(customKey >= '0' && customKey <= '9')
    {
      secondNum = secondNum * 10 + (customKey - '0');
      lcd.setCursor(0,2);
      lcd.print(secondNum);
    }

    if(customKey == '=') break;
  }
 return secondNum; 
}

Oct 07,2022

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