Code

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

// --- Configuration ---
const char* masterCode = "1234"; // Set your 4-digit PIN here
const int relayPin = 16;         // D0 on NodeMCU
const int lockDelay = 3000;      // How long the door stays open (ms)

// --- Keypad Setup ---
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] = {D3, D4, D5, D6}; 
byte colPins[COLS] = {D7, D8, 3, 1}; // 3 is RX, 1 is TX

Keypad keypad = Keypad(makeKeymap(keys), rowPins, colPins, ROWS, COLS);
LiquidCrystal_I2C lcd(0x27, 16, 2); // Change 0x27 to 0x3F if it doesn't work

String inputCode = "";

void setup() {
  pinMode(relayPin, OUTPUT);
  digitalWrite(relayPin, LOW); // Ensure lock is closed
  
  lcd.init();
  lcd.backlight();
  showIdleMessage();
}

void loop() {
  char key = keypad.getKey();

  if (key) {
    if (key == '#') { // Submit Key
      checkCode();
    } else if (key == '*') { // Clear Key
      resetInput();
    } else {
      inputCode += key;
      lcd.setCursor(inputCode.length() - 1, 1);
      lcd.print('*'); // Mask the input for security
    }
  }
}

void checkCode() {
  lcd.clear();
  if (inputCode == masterCode) {
    lcd.print("Access Granted");
    digitalWrite(relayPin, HIGH); // Open Lock
    delay(lockDelay);
    digitalWrite(relayPin, LOW);  // Close Lock
  } else {
    lcd.print("Invalid Code!");
    delay(2000);
  }
  resetInput();
}

void resetInput() {
  inputCode = "";
  showIdleMessage();
}

void showIdleMessage() {
  lcd.clear();
  lcd.print("Enter Code:");
  lcd.setCursor(0, 1);
}