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@suadanwar
Created September 19, 2019 09:20
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This sample code is for Calculator Using 4x4 Keypad and I2C LCD on Arduino.
#include <LiquidCrystal_I2C.h>
LiquidCrystal_I2C lcd(0x27, 20, 2); // set the LCD address to 0x27 for a 16 chars and 2 line display
#include <Keypad.h>
const byte ROWS = 4;
const byte COLS = 4;
char keys [ROWS] [COLS] = {
{'1', '2', '3', '+'},
{'4', '5', '6', '-'},
{'7', '8', '9', '*'},
{'C', '0', '=', '/'}
};
byte rowPins[ROWS] = {10, 9, 7, 6};
byte colPins[COLS] = {5, 4, 3, 2};
Keypad myKeypad = Keypad( makeKeymap(keys), rowPins, colPins, ROWS, COLS );
boolean presentValue = false;
boolean next = false;
boolean final = false;
String num1, num2;
int answer = 0;
char op;
void setup()
{
lcd.init();
lcd.backlight();
lcd.setCursor(3,0);
lcd.print("Maker UNO");
lcd.setCursor(3,1);
lcd.print("Calculator");
delay(3000);
lcd.clear();
}
void loop() {
char key = myKeypad.getKey();
if (key != NO_KEY && (key == '1' || key == '2' || key == '3' || key == '4' || key == '5' || key == '6' || key == '7' || key == '8' || key == '9' || key == '0'))
{
if (presentValue != true)
{
num1 = num1 + key;
int numLength = num1.length();
lcd.setCursor(0, 0);
lcd.print(num1);
}
else
{
num2 = num2 + key;
int numLength = num2.length();
int numLength1 = num1.length();
lcd.setCursor(1 + numLength1, 0);
lcd.print(num2);
final = true;
}
}
else if (presentValue == false && key != NO_KEY && (key == '/' || key == '*' || key == '-' || key == '+'))
{
if (presentValue == false)
{
int numLength = num1.length();
presentValue = true;
op = key;
lcd.setCursor(0 + numLength, 0);
lcd.print(op);
}
}
else if (final == true && key != NO_KEY && key == '=') {
if (op == '+') {
answer = num1.toInt() + num2.toInt();
}
else if (op == '-') {
answer = num1.toInt() - num2.toInt();
}
else if (op == '*') {
answer = num1.toInt() * num2.toInt();
}
else if (op == '/') {
answer = num1.toInt() / num2.toInt();
}
lcd.clear();
lcd.setCursor(16, 1);
lcd.autoscroll();
lcd.print(answer);
lcd.noAutoscroll();
}
else if (key != NO_KEY && key == 'C') {
lcd.clear();
presentValue = false;
final = false;
num1 = "";
num2 = "";
answer = 0;
op = ' ';
}
}
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