Smart Classroom Safety System

#include <Arduino.h>
#include <Wire.h>
#include <DHT.h>
#include <TM1637Display.h>
#include <SPI.h>
#include <MFRC522.h>
#include <MPU6050.h>

// ── Pin Definitions ───────────────────────────────────────────
#define DHT_PIN          7
#define FAN_LED_PIN      6    // Green LED — lights when temp >= threshold
#define BUZZER_PIN       5
#define DND_LED_PIN      4
#define SOUND_DO_PIN     17   // A3 used as digital input
#define WATER_POWER_PIN  12   // Pulse power to reduce electrode corrosion
#define WATER_S_PIN      A0   // Analog water level signal

#define SEG_CLK_PIN      8
#define SEG_DIO_PIN      9

#define RFID_SS_PIN      10
#define RFID_RST_PIN     11

// ── Thresholds ────────────────────────────────────────────────
#define TEMP_HOT_C          30.0f
#define HUMID_FLOOD_PCT     80.0f
#define WATER_LEVEL_THRESH  400
#define NOISE_DURATION_MS   3000UL
#define QUAKE_THRESHOLD     15000L   // raw accel magnitude above 1g baseline
#define CLASS_DURATION_SECS (45L * 60L)

// ── Enrolled RFID UIDs ────────────────────────────────────────
// Scan an unknown card → Serial prints its UID → paste bytes here.
struct RfidCard {
  byte uid[4];
  const char* name;
};


// Forward declarations
int readWater();
void showCountdown(long secs);
void showSegDashes();
const char* lookupUid(MFRC522::Uid &u);

static const RfidCard ENROLLED[] = {
  { {0xDE, 0xAD, 0xBE, 0xEF}, "Teacher"   },
  { {0x11, 0x22, 0x33, 0x44}, "Student 1" },
  { {0x55, 0x66, 0x77, 0x88}, "Student 2" },
};
static const uint8_t ENROLLED_COUNT = sizeof(ENROLLED) / sizeof(ENROLLED[0]);

// ── Objects ───────────────────────────────────────────────────
DHT          dht(DHT_PIN, DHT11);
TM1637Display seg(SEG_CLK_PIN, SEG_DIO_PIN);
MFRC522      rfid(RFID_SS_PIN, RFID_RST_PIN);
MPU6050      mpu;

// ── State ─────────────────────────────────────────────────────
float lastT = 25.0f, lastH = 50.0f;
int   waterLevel  = 0;
bool  noiseActive = false;
bool  dndActive   = false;
unsigned long noiseSince = 0;
unsigned long lastSensor = 0;
unsigned long lastWater  = 0;

// Timer
bool  timerRunning   = false;
long  countdownSecs  = 0;
unsigned long timerLastTick = 0;

// Earthquake
bool  quakeAlert = false;
unsigned long quakeTime = 0;

// Attendance
int  attendanceCount = 0;

// ── Helpers ───────────────────────────────────────────────────
int readWater() {
  digitalWrite(WATER_POWER_PIN, HIGH);
  delayMicroseconds(500);
  int v = analogRead(WATER_S_PIN);
  digitalWrite(WATER_POWER_PIN, LOW);
  return v;
}

void showCountdown(long secs) {
  if (secs < 0) secs = 0;
  int m = (int)(secs / 60);
  int s = (int)(secs % 60);
  seg.showNumberDecEx(m * 100 + s, 0x40, true);
}

void showSegDashes() {
  uint8_t d[4] = {0x40, 0x40, 0x40, 0x40};
  seg.setSegments(d);
}

const char* lookupUid(MFRC522::Uid &u) {
  if (u.size != 4) return nullptr;
  for (uint8_t i = 0; i < ENROLLED_COUNT; i++) {
    if (memcmp(u.uidByte, ENROLLED[i].uid, 4) == 0)
      return ENROLLED[i].name;
  }
  return nullptr;
}

// ── Setup ─────────────────────────────────────────────────────
void setup() {
  Serial.begin(9600);

  pinMode(FAN_LED_PIN,     OUTPUT);
  pinMode(BUZZER_PIN,      OUTPUT);
  pinMode(DND_LED_PIN,     OUTPUT);
  pinMode(WATER_POWER_PIN, OUTPUT);
  pinMode(SOUND_DO_PIN,    INPUT);

  digitalWrite(FAN_LED_PIN,     LOW);
  digitalWrite(BUZZER_PIN,      LOW);
  digitalWrite(DND_LED_PIN,     LOW);
  digitalWrite(WATER_POWER_PIN, LOW);

  dht.begin();

  seg.setBrightness(5);
  showSegDashes();

  Wire.begin();
  SPI.begin();
  rfid.PCD_Init();

  mpu.initialize();
  if (!mpu.testConnection()) {
    Serial.println(F("MPU6050 not found — check wiring"));
  }

  // Auto-start 45-minute class timer
  countdownSecs = CLASS_DURATION_SECS;
  timerLastTick = millis();
  timerRunning  = true;

  Serial.println(F("=== Smart Classroom Ready ==="));
  Serial.print(F("45-min timer started | Enrolled cards: "));
  Serial.println(ENROLLED_COUNT);
  Serial.println(F("Sensors: DHT11 | Water | Sound | MPU6050 | RFID"));
}

// ── Loop ──────────────────────────────────────────────────────
void loop() {
  unsigned long now = millis();

  // ── 1. DHT11 every 2 s ──────────────────────────────────────
  if (now - lastSensor >= 2000) {
    lastSensor = now;
    float t = dht.readTemperature();
    float h = dht.readHumidity();
    if (!isnan(t)) lastT = t;
    if (!isnan(h)) lastH = h;
  }

  // ── 2. Fan/heat LED ─────────────────────────────────────────
  digitalWrite(FAN_LED_PIN, lastT >= TEMP_HOT_C ? HIGH : LOW);

  // ── 3. Water level every 1 s ────────────────────────────────
  if (now - lastWater >= 1000) {
    lastWater  = now;
    waterLevel = readWater();
  }
  bool floodAlert = (lastH >= HUMID_FLOOD_PCT) && (waterLevel >= WATER_LEVEL_THRESH);

  // ── 4. MPU6050 earthquake detection ─────────────────────────
  int16_t ax, ay, az, gx, gy, gz;
  mpu.getMotion6(&ax, &ay, &az, &gx, &gy, &gz);
  // Subtract gravity (1g ≈ 16384 in ±2g range) from Z axis
  int32_t mag = (int32_t)abs(ax) + abs(ay) + abs((int16_t)(az - 16384));
  if (mag > QUAKE_THRESHOLD && !quakeAlert) {
    quakeAlert = true;
    quakeTime  = now;
    Serial.println(F("!! EARTHQUAKE ALERT — SEEK COVER !!"));
  }
  if (quakeAlert && (now - quakeTime >= 10000)) {
    quakeAlert = false;
    Serial.println(F("Quake alert cleared."));
  }

  // ── 5. Buzzer: quake > flood > dismissed ────────────────────
  if (quakeAlert) {
    // Rapid double-beep
    uint8_t phase = (uint8_t)((now / 150) % 4);
    digitalWrite(BUZZER_PIN, (phase == 0 || phase == 2) ? HIGH : LOW);
  } else if (floodAlert) {
    digitalWrite(BUZZER_PIN, (now / 500) % 2 == 0 ? HIGH : LOW);
  } else if (!timerRunning && countdownSecs == 0) {
    // Class dismissed — slow beep for 10 s then stop
    unsigned long elapsed = now - timerLastTick;
    if (elapsed < 10000) {
      digitalWrite(BUZZER_PIN, (now / 600) % 2 == 0 ? HIGH : LOW);
    } else {
      digitalWrite(BUZZER_PIN, LOW);
    }
  } else {
    digitalWrite(BUZZER_PIN, LOW);
  }

  // ── 6. Sound / noise detection ──────────────────────────────
  bool soundHigh = (digitalRead(SOUND_DO_PIN) == HIGH);
  if (soundHigh) {
    if (noiseSince == 0) noiseSince = now;
    noiseActive = (now - noiseSince >= NOISE_DURATION_MS);
  } else {
    noiseSince  = 0;
    noiseActive = false;
  }
  if (noiseActive) {
    static bool noisePrinted = false;
    if (!noisePrinted) {
      Serial.println(F("NOISE ALERT — classroom too loud!"));
      noisePrinted = true;
    }
  } else {
    static bool noisePrinted = false;
    noisePrinted = false;
  }

  // ── 7. RFID attendance ──────────────────────────────────────
  if (rfid.PICC_IsNewCardPresent() && rfid.PICC_ReadCardSerial()) {
    const char* name = lookupUid(rfid.uid);
    if (name) {
      attendanceCount++;
      Serial.print(F("ATTENDANCE: "));
      Serial.print(name);
      Serial.print(F("  #"));
      Serial.println(attendanceCount);
      // Teacher card toggles DND
      if (strcmp(name, "Teacher") == 0) {
        dndActive = !dndActive;
        Serial.print(F("DND: "));
        Serial.println(dndActive ? F("ON") : F("OFF"));
      }
    } else {
      Serial.print(F("UNKNOWN CARD UID: "));
      for (byte i = 0; i < rfid.uid.size; i++) {
        if (rfid.uid.uidByte[i] < 0x10) Serial.print('0');
        Serial.print(rfid.uid.uidByte[i], HEX);
        if (i < rfid.uid.size - 1) Serial.print(',');
      }
      Serial.println();
    }
    rfid.PICC_HaltA();
    rfid.PCD_StopCrypto1();
  }

  // ── 8. DND LED ──────────────────────────────────────────────
  digitalWrite(DND_LED_PIN, dndActive ? HIGH : LOW);

  // ── 9. Countdown timer ──────────────────────────────────────
  if (timerRunning) {
    if (now - timerLastTick >= 1000) {
      timerLastTick += 1000;
      if (--countdownSecs <= 0) {
        countdownSecs = 0;
        timerRunning  = false;
        timerLastTick = now;    // reuse as dismissed-at timestamp for buzzer
        Serial.println(F("*** CLASS DISMISSED ***"));
      }
    }
    showCountdown(countdownSecs);
  } else if (countdownSecs == 0) {
    // Flash 00:00
    if ((now / 500) % 2 == 0) {
      seg.showNumberDecEx(0, 0x40, true);
    } else {
      uint8_t blank[4] = {0, 0, 0, 0};
      seg.setSegments(blank);
    }
  } else {
    showSegDashes();
  }

  // ── 10. Serial heartbeat every 10 s ─────────────────────────
  static unsigned long lastSerial = 0;
  if (now - lastSerial >= 10000) {
    lastSerial = now;
    Serial.print(F("T:"));    Serial.print(lastT, 1);
    Serial.print(F("C H:")); Serial.print(lastH, 1);
    Serial.print(F("% | Water:"));  Serial.print(waterLevel);
    Serial.print(F(" | Flood:"));   Serial.print(floodAlert  ? F("YES") : F("no"));
    Serial.print(F(" | Quake:"));   Serial.print(quakeAlert  ? F("YES") : F("no"));
    Serial.print(F(" | Noise:"));   Serial.print(noiseActive ? F("YES") : F("no"));
    Serial.print(F(" | DND:"));     Serial.print(dndActive   ? F("ON")  : F("off"));
    Serial.print(F(" | Timer:"));   Serial.print(countdownSecs);
    Serial.print(F("s | Attn:"));   Serial.println(attendanceCount);
  }
}