#include <Wire.h> 
#include <LiquidCrystal_I2C.h> 
#include "DHT.h" 
// Pin Assignments 
#define DHT_PIN     15     // DHT22 data pin 
#define PIR_PIN     14     // PIR sensor output pin 
#define MQ2_PIN     35     // MQ-2 analog output (ESP32 ADC pin) 
#define LDR_PIN     34     // LDR analog output (ESP32 ADC pin) 
#define TRIG_PIN    12     // HC-SR04 trigger pin 
#define ECHO_PIN    13     // HC-SR04 echo pin 
#define RELAY1_PIN   5     // Relay1 control (light) 
#define RELAY2_PIN  16     // Relay2 control (fan) 
#define RELAY3_PIN  17     // Relay3 control (buzzer/alarm) 
#define RELAY4_PIN  18     // Relay4 control (other appliance) 
#define LED1_R_PIN  19     // RGB LED1 Red 
#define LED1_G_PIN  23     // RGB LED1 Green 
#define LED1_B_PIN  25     // RGB LED1 Blue 
#define LED2_R_PIN  26     // RGB LED2 Red 
#define LED2_G_PIN  27     // RGB LED2 Green 
#define LED2_B_PIN  32     // RGB LED2 Blue 
#define LED3_R_PIN  33     // RGB LED3 Red 
#define LED3_G_PIN   4     // RGB LED3 Green 
#define LED3_B_PIN   2     // RGB LED3 Blue 
 
// Sensor and system thresholds 
const float TEMP_THRESHOLD = 30.0;    // [°C] Temperature above which fan turns on 
const int   LDR_THRESHOLD  = 3000;    // LDR analog value above which we consider it "dark" 
const int   GAS_THRESHOLD  = 40;      // [%] Gas level above which alarm triggers 
const float DIST_THRESHOLD = 50.0;    // [cm] Distance below which an object is considered 
"detected" 
 
// Initialize DHT22 (using Adafruit DHT library) 
#define DHTTYPE DHT22 
DHT dht(DHT_PIN, DHTTYPE); 
 
// Initialize LCD (I2C address 0x27, 16 columns, 2 rows) 
LiquidCrystal_I2C lcd(0x27, 16, 2); 
 
void setup() { 
  // Serial port for debugging 
  Serial.begin(115200); 
  Serial.println("ESP32 Home Automation System Starting...");
   // Initialize DHT sensor 
  dht.begin(); 
 
  // Initialize LCD 
  lcd.init(); 
  lcd.backlight(); 
  lcd.setCursor(0, 0); 
  lcd.print("ESP32 Home IoT"); 
  lcd.setCursor(0, 1); 
  lcd.print("System Starting"); 
  delay(2000);  // display startup message for 2 seconds 
  lcd.clear(); 
 
  // Configure sensor pins 
  pinMode(PIR_PIN, INPUT);         // PIR (could use INPUT_PULLUP if needed) 
  pinMode(TRIG_PIN, OUTPUT);       // Ultrasonic Trigger 
  pinMode(ECHO_PIN, INPUT);        // Ultrasonic Echo 
 
  // Configure relay output pins 
  pinMode(RELAY1_PIN, OUTPUT); 
  pinMode(RELAY2_PIN, OUTPUT); 
  pinMode(RELAY3_PIN, OUTPUT);
    pinMode(RELAY4_PIN, OUTPUT); 
  // Ensure all relays off initially 
  digitalWrite(RELAY1_PIN, LOW); 
  digitalWrite(RELAY2_PIN, LOW); 
  digitalWrite(RELAY3_PIN, LOW); 
  digitalWrite(RELAY4_PIN, LOW); 
 
  // Configure RGB LED pins as outputs 
  pinMode(LED1_R_PIN, OUTPUT); pinMode(LED1_G_PIN, OUTPUT); pinMode(LED1_B_PIN, 
OUTPUT); 
  pinMode(LED2_R_PIN, OUTPUT); pinMode(LED2_G_PIN, OUTPUT); pinMode(LED2_B_PIN, 
OUTPUT); 
  pinMode(LED3_R_PIN, OUTPUT); pinMode(LED3_G_PIN, OUTPUT); pinMode(LED3_B_PIN, 
OUTPUT); 
  // Turn all RGB LEDs off initially 
  digitalWrite(LED1_R_PIN, LOW); digitalWrite(LED1_G_PIN, LOW); digitalWrite(LED1_B_PIN, 
LOW); 
  digitalWrite(LED2_R_PIN, LOW); digitalWrite(LED2_G_PIN, LOW); digitalWrite(LED2_B_PIN, 
LOW); 
  digitalWrite(LED3_R_PIN, LOW); digitalWrite(LED3_G_PIN, LOW); digitalWrite(LED3_B_PIN, 
LOW); 
} 
 
void loop() { 
  // 1. Read sensors
   // Read DHT22 temperature and humidity 
  float temperature = dht.readTemperature();    // in °C 
  float humidity    = dht.readHumidity();       // in % 
  if (isnan(temperature) || isnan(humidity)) { 
    // If reading failed, print error and skip the rest of loop iteration 
    Serial.println("Error reading from DHT22 sensor!"); 
    // We won't update LCD or outputs this cycle if DHT fails, to avoid false triggers 
  } else { 
    // Read PIR motion sensor 
    int motionVal = digitalRead(PIR_PIN);  // HIGH if motion, LOW if no motion 
 
    // Read MQ-2 gas sensor (analog value) 
    int gasAnalog = analogRead(MQ2_PIN);       // 0-4095 
    int gasPercent = map(gasAnalog, 0, 4095, 0, 100);  // rough conversion to 0-100% 
 
    // Read LDR sensor (analog value) 
    int lightAnalog = analogRead(LDR_PIN);     // 0-4095 (higher = darker if pull-down used) 
 
    // Read Ultrasonic distance (in cm) 
    float distance = 0.0; 
    // Trigger the ultrasonic pulse 
    digitalWrite(TRIG_PIN, LOW); 
    delayMicroseconds(2);
       digitalWrite(TRIG_PIN, HIGH); 
    delayMicroseconds(10); 
    digitalWrite(TRIG_PIN, LOW); 
    // Measure the echo pulse width 
    long duration_us = pulseIn(ECHO_PIN, HIGH, 30000); // 30ms timeout (~5m) 
    if (duration_us > 0) { 
      distance = (duration_us * 0.0343) / 2.0;  // speed of sound: 0.0343 cm/us 
    } else { 
      distance = 999.0; // if no echo, set distance to a large value (no object or out of range) 
    } 
 
    // 2. Update LCD display 
    char line1[17]; char line2[17]; 
    // Prepare formatted strings for each line (ensure they fit 16 chars) 
    snprintf(line1, sizeof(line1), "Temp:%.1fC Hum:%.0f%%", temperature, humidity); 
    // Gas displayed as %, LDR as raw (or could convert to % brightness) 
    snprintf(line2, sizeof(line2), "Gas:%d%% LDR:%4d", gasPercent, lightAnalog); 
    lcd.setCursor(0, 0); 
    lcd.print(line1); 
    lcd.setCursor(0, 1); 
    lcd.print(line2); 
 
    // 3. Print to Serial Monitor
     Serial.print("Temperature: "); Serial.print(temperature); Serial.println(" C"); 
    Serial.print("Humidity:    "); Serial.print(humidity);    Serial.println(" %"); 
    Serial.print("Light (LDR): "); Serial.println(lightAnalog); 
    Serial.print("Gas level:   "); Serial.print(gasPercent);  Serial.println(" %"); 
    Serial.print("Motion:      "); 
    if (motionVal == HIGH) Serial.println("DETECTED"); 
    else                   Serial.println("None"); 
    Serial.print("Distance:    "); Serial.print(distance); Serial.println(" cm"); 
    Serial.println("------------------------"); 
 
    // 4. Control Outputs based on sensor values 
 
    // Relay1 and Room Light LED (motion + darkness -> light on) 
    if (motionVal == HIGH && lightAnalog > LDR_THRESHOLD) { 
      digitalWrite(RELAY1_PIN, HIGH);  // turn on light 
    } else { 
      digitalWrite(RELAY1_PIN, LOW);   // turn off light 
    } // (We could also add a small timer to hold the light on for a while after motion)  
 // Relay2 and Temp  
LED (high temp -> fan on) 
    if (temperature >= TEMP_THRESHOLD) { 
      digitalWrite(RELAY2_PIN, HIGH);  // turn on fan/AC 
      // LED1 Red for hot
          digitalWrite(LED1_R_PIN, HIGH); 
      digitalWrite(LED1_G_PIN, LOW); 
      digitalWrite(LED1_B_PIN, LOW); 
    } else { 
      digitalWrite(RELAY2_PIN, LOW);   // turn off fan/AC// LED1 Blue for comfortable 
      digitalWrite(LED1_R_PIN, LOW); 
      digitalWrite(LED1_G_PIN, LOW); 
      digitalWrite(LED1_B_PIN, HIGH); 
    }// Relay3 and Gas LED (gas above threshold -> alarm on) 
    if (gasPercent >= GAS_THRESHOLD) { 
      digitalWrite(RELAY3_PIN, HIGH);  // trigger alarm 
      // LED3 Red for gas danger 
      digitalWrite(LED3_R_PIN, HIGH); 
      digitalWrite(LED3_G_PIN, LOW); 
      digitalWrite(LED3_B_PIN, LOW); 
    } else { 
      digitalWrite(RELAY3_PIN, LOW);   // alarm off 
      // LED3 Green for safe 
      digitalWrite(LED3_R_PIN, LOW); 
      digitalWrite(LED3_G_PIN, HIGH); 
      digitalWrite(LED3_B_PIN, LOW); 
    }// Relay4 (distance-based trigger, e.g., open door if object is very close) 
    if (distance > 0 && distance < DIST_THRESHOLD) {
         digitalWrite(RELAY4_PIN, HIGH);  // object detected within range 
    } else { 
      digitalWrite(RELAY4_PIN, LOW); 
    }// RGB LED2 indicates motion status (simple ON/OFF via green channel) 
    if (motionVal == HIGH) {// Motion detected: LED2 Green ON 
      digitalWrite(LED2_G_PIN, HIGH); 
    } else { // No motion: LED2 off 
      digitalWrite(LED2_G_PIN, LOW); 
    }  // (LED2_R and LED2_B are not used in this project scenario, keep them off) 
    digitalWrite(LED2_R_PIN, LOW); 
    digitalWrite(LED2_B_PIN, LOW); 
  } 
  // 5. Loop delay 
  delay(2000);  // wait 2 seconds before next sensor read cycle
}