#include <Keypad.h>
#include <Wire.h>
#include <LiquidCrystal_I2C.h>

LiquidCrystal_I2C lcd(0x27, 16, 2); // Set the LCD address to 0x27 for a 16 chars and 2 line display

const int numRows = 4;
const int numCols = 4;
char keys[numRows][numCols] = {
  {'1','2','3','A'},
  {'4','5','6','B'},
  {'7','8','9','C'},
  {'*','0','#','D'}
};

byte rowPins[numRows] = {0,1,2,3}; //connect to the row pinouts of the keypad
byte colPins[numCols] = {A0,A1,A2,A3}; //connect to the column pinouts of the keypad

void setup() {
  Serial.begin(9600);
  lcd.init();                      // initialize the lcd 
  lcd.backlight();
  lcd.print("Hello World");
  delay(3000);
  lcd.clear();
}

void loop() {
  char key = getKey();
  
  if (key != NO_KEY) {
    lcd.clear();
    lcd.setCursor(0, 0);
    lcd.print("Pressed Key:");
    lcd.setCursor(0, 1);
    lcd.print(key);
    delay(1000);
  }
}

char getKey() {
  char key = NO_KEY;
  for (int i = 0; i < numCols; i++) {
    pinMode(colPins[i], OUTPUT);
    digitalWrite(colPins[i], LOW);

    for (int j = 0; j < numRows; j++) {
      pinMode(rowPins[j], INPUT_PULLUP);
      if (digitalRead(rowPins[j]) == LOW) {
        key = keys[j][i];
        while (digitalRead(rowPins[j]) == LOW)
          delay(10);
      }
      pinMode(rowPins[j], INPUT);
    }

    pinMode(colPins[i], INPUT);
    digitalWrite(colPins[i], HIGH);
  }
  return key;
}