DIY Smart Lock: Arduino + Rack & Pinion + Keypad

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

// --- LCD Configuration ---
LiquidCrystal_I2C lcd(0x27, 16, 2);

// --- Servo ---
Servo lockServo;

// --- Keypad Configuration ---
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] = {2, 3, 4, 5};
byte colPins[COLS] = {6, 7, 9, 8};  // Note: matches first code's pin order

Keypad keypad = Keypad(makeKeymap(keys), rowPins, colPins, ROWS, COLS);

// --- Pin Definitions ---
#define RED_LED    12
#define GREEN_LED  13
#define SERVO_PIN  10
#define BUZZER     11

// --- Password Logic ---
String correctPassword = "1234";
String enteredPassword = "";

void setup() {
  Serial.begin(9600);

  // Initialize LCD
  lcd.init();
  lcd.backlight();

  // Initialize pins
  pinMode(RED_LED,   OUTPUT);
  pinMode(GREEN_LED, OUTPUT);
  pinMode(BUZZER,    OUTPUT);

  // Initialize Servo
  lockServo.attach(SERVO_PIN);
  lockServo.write(90);  // Locked position

  // Default state: locked
  digitalWrite(RED_LED,   HIGH);
  digitalWrite(GREEN_LED, LOW);

  // --- Startup Test (from first code) ---
  lcd.print("System Testing");

  // LED Test
  lcd.setCursor(0, 1);
  lcd.print("Testing LEDs... ");
  digitalWrite(RED_LED, HIGH);  delay(500);
  digitalWrite(RED_LED, LOW);
  digitalWrite(GREEN_LED, HIGH); delay(500);
  digitalWrite(GREEN_LED, LOW);

  // Buzzer Test
  lcd.clear();
  lcd.print("Buzzer: BEEP");
  digitalWrite(BUZZER, HIGH); delay(150);
  digitalWrite(BUZZER, LOW);

  // Servo Test
  lcd.clear();
  lcd.print("Servo: Testing");
  lockServo.write(0); delay(1000);
  lockServo.write(90);  delay(1000);

  lcd.clear();
  lcd.print("Test Complete!");
  delay(1000);

  // Set locked state and show prompt
  digitalWrite(RED_LED, HIGH);
  resetSystem();

  Serial.println("--- System Online: Waiting for Input ---");
}

void loop() {
  char key = keypad.getKey();  // Uses Keypad library (no manual scan needed)

  if (key) {
    Serial.print(key);

    if (key == '#') {
      Serial.println("\n--- SUBMIT BUTTON PRESSED ---");
      processPassword();
    }
    else if (key == '*') {
      Serial.println("\n--- CLEAR BUTTON PRESSED ---");
      resetSystem();
    }
    else {
      if (enteredPassword.length() < 8) {
        enteredPassword += key;

        // Show asterisk for each character
        lcd.setCursor(enteredPassword.length() - 1, 1);
        lcd.print('*');

        Serial.print("Typed: ");        Serial.print(key);
        Serial.print(" | Buffer: ");    Serial.println(enteredPassword);

        // Key press beep
        digitalWrite(BUZZER, HIGH); delay(50);
        digitalWrite(BUZZER, LOW);
      }
    }
  }
}

void processPassword() {
  Serial.print("Entered: [");   Serial.print(enteredPassword); Serial.println("]");
  Serial.print("Expected: [");  Serial.print(correctPassword); Serial.println("]");

  lcd.clear();
  enteredPassword.trim();

  if (enteredPassword == correctPassword) {
    Serial.println(">>> RESULT: MATCH FOUND! <<<");
    lcd.print("Access Granted!");

    digitalWrite(RED_LED,   LOW);
    digitalWrite(GREEN_LED, HIGH);

    lockServo.write(0);  // Unlock
    delay(3000);
    lockServo.write(90);   // Lock again

    digitalWrite(GREEN_LED, LOW);
    digitalWrite(RED_LED,   HIGH);
  }
  else {
    Serial.println(">>> RESULT: NO MATCH! <<<");
    lcd.print("Wrong Password!");

    for (int i = 0; i < 4; i++) {
      digitalWrite(BUZZER, HIGH); delay(150);
      digitalWrite(BUZZER, LOW);  delay(150);
    }
  }

  resetSystem();
}

void resetSystem() {
  enteredPassword = "";
  lcd.clear();
  lcd.print("Enter Password:");
  lcd.setCursor(0, 1);
}