Arduino-Smart-Lock.ino

#include <Keypad.h>
#include <LiquidCrystal.h>
#include <Servo.h>

#define PWD_LEN 5
#define SERVO_PIN 10
#define LOCK_TIMEOUT 4000
#define PENALTY_TIMEOUT 10000

// --- FINITE STATE MACHINE STATES ---
#define STATE_BOOT 0
#define STATE_LOCKED 1
#define STATE_INPUT 2
#define STATE_EVALUATE 3
#define STATE_UNLOCKED 4
#define STATE_LOCKOUT 5

int currentState = STATE_BOOT;

// --- HARDWARE INTERFACES ---
Servo myservo;
const int rs = A0, en = A1, d4 = A2, d5 = A3, d6 = A4, d7 = A5;
LiquidCrystal lcd(rs, en, d4, d5, d6, d7);

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] = {0, 1, 2, 3};
byte colPins[COLS] = {4, 5, 6, 7};
Keypad customKeypad = Keypad(makeKeymap(keys), rowPins, colPins, ROWS, COLS);

// --- VARIABLES ---
char Data[PWD_LEN];
char Master[PWD_LEN] = "A753";
byte data_count = 0;
byte failed_attempts = 0;
unsigned long stateTimer = 0;
int last_sec = -1; // Tracks the last displayed second to prevent LCD flickering

// --- FUNCTION PROTOTYPES ---
void TransitionTo(int nextState);
void ProcessKeypadInput();
void UnlockDoor();
void LockDoor();
void HandleFailedAttempt();
void clearData();

void setup()
{
    myservo.attach(SERVO_PIN);
    myservo.write(90); // Initialize locked position

    lcd.begin(16, 2);
    lcd.print("System Booting..");

    stateTimer = millis();
    currentState = STATE_BOOT;
}

void loop()
{
    // FINITE STATE MACHINE CONTROLLER
    switch (currentState)
    {

    case STATE_BOOT:
        if (millis() - stateTimer >= 2000)
        {
            lcd.clear();
            TransitionTo(STATE_LOCKED);
        }
        break;

    case STATE_LOCKED:
        lcd.setCursor(0, 0);
        lcd.print("Enter Password:");
        TransitionTo(STATE_INPUT);
        break;

    case STATE_INPUT:
        ProcessKeypadInput();
        if (data_count == PWD_LEN - 1)
        {
            TransitionTo(STATE_EVALUATE);
        }
        break;

    case STATE_EVALUATE:
        Data[data_count] = '\0'; // Null terminate for safety
        if (!strcmp(Data, Master))
        {
            failed_attempts = 0;
            UnlockDoor();
            stateTimer = millis();
            TransitionTo(STATE_UNLOCKED);
        }
        else
        {
            failed_attempts++;
            HandleFailedAttempt();
        }
        clearData();
        break;

    case STATE_UNLOCKED:
        if (millis() - stateTimer >= LOCK_TIMEOUT)
        {
            LockDoor();
            TransitionTo(STATE_LOCKED);
        }
        break;

    case STATE_LOCKOUT:
    {
        unsigned long elapsed = millis() - stateTimer;

        // If the penalty time is over, unlock the system
        if (elapsed >= PENALTY_TIMEOUT)
        {
            failed_attempts = 0;
            lcd.clear();
            TransitionTo(STATE_LOCKED);
        }
        else
        {
            // Calculate remaining seconds (+999 ensures it rounds up beautifully from 10 down to 1)
            int remaining_sec = (PENALTY_TIMEOUT - elapsed + 999) / 1000;

            // Only update the LCD if the second has actually changed
            if (remaining_sec != last_sec)
            {
                lcd.setCursor(0, 1);
                lcd.print("Wait: ");
                lcd.print(remaining_sec);
                lcd.print(" Sec   "); // Extra spaces clear leftover characters like the '0' from '10'
                last_sec = remaining_sec;
            }
        }
    }
    break;
    }
}

// --- HELPER FUNCTIONS ---

void TransitionTo(int nextState)
{
    currentState = nextState;
}

void ProcessKeypadInput()
{
    char customKey = customKeypad.getKey();
    if (customKey)
    {
        if (customKey == 'C')
        { // Input correction
            clearData();
            lcd.clear();
            TransitionTo(STATE_LOCKED);
            return;
        }
        Data[data_count] = customKey;
        lcd.setCursor(data_count, 1);
        lcd.print('*');
        data_count++;
    }
}

void UnlockDoor()
{
    lcd.clear();
    lcd.print("Access Granted");
    myservo.write(0); // Open
}

void LockDoor()
{
    lcd.clear();
    lcd.print("Securing...");
    myservo.write(90); // Close
    delay(500);
    lcd.clear();
}

void HandleFailedAttempt()
{
    lcd.clear();
    lcd.print("Access Denied");
    lcd.setCursor(0, 1);
    lcd.print("Attempts: ");
    lcd.print(failed_attempts);

    delay(1500);

    if (failed_attempts >= 3)
    {
        lcd.clear();
        lcd.print("SYSTEM LOCKED");
        last_sec = -1; // Reset our LCD tracker for the countdown
        stateTimer = millis();
        TransitionTo(STATE_LOCKOUT);
    }
    else
    {
        lcd.clear();
        TransitionTo(STATE_LOCKED);
    }
}

void clearData()
{
    memset(Data, 0, sizeof(Data));
    data_count = 0;
}