#include <Wire.h> // include I2C library
#include <LiquidCrystal_I2C.h> // include LCD library
#include <Keypad.h> // include keypad library

// Define keypad pins and keypad matrix
const byte ROWS = 4;
const byte COLS = 4;
char keys[ROWS][COLS] = {
  {'1', '2', '3', 'A'},
  {'4', '5', '6', 'B'},
  {'7', '8', '9', 'C'},
  {'*', '0', '#', 'D'}
};
byte rowPins[ROWS] = {22, 24, 26, 28};
byte colPins[COLS] = {34, 36, 38, 40};

// Initialize keypad and LCD
Keypad keypad = Keypad(makeKeymap(keys), rowPins, colPins, ROWS, COLS);
LiquidCrystal_I2C lcd(0x27, 16, 2);

char key = ' ';
char key2 = ' ';

void setup() {
  // Initialize serial communication
  Serial.begin(9600);
  
  // Initialize LCD
  lcd.init();
  lcd.backlight();
  lcd.clear();
  lcd.setCursor(0, 0);
  lcd.print("Welcome to");
  lcd.setCursor(0, 1);
  lcd.print("my project!");

  delay(2000); // wait 2 seconds

  lcd.clear();
  lcd.setCursor(0, 0);
  lcd.print("Waiting");
}

void loop() {
  char tempKey = keypad.getKey();
  
  if (tempKey != NO_KEY) {
    key2 = key;
    key = tempKey;
    
    Serial.println(key);

    // Display the last key pressed on the top row of the LCD
    lcd.setCursor(0, 0);
    lcd.print("Last key: ");
    lcd.print(key2);

    // Display the new key pressed on the bottom row of the LCD
    lcd.setCursor(0, 1);
    lcd.print("New key: ");
    lcd.print(key);
    
    while (keypad.getState() == PRESSED && keypad.getKey() == key) {
      delay(1000); // debounce delay
    }
  }
}