updated mq2

#include <WiFi.h>
#include <HTTPClient.h>
#include <Wire.h>
#include <Adafruit_SSD1306.h>
#include <Adafruit_GFX.h>

#define SCREEN_WIDTH 128  // OLED display width
#define SCREEN_HEIGHT 64  // OLED display height
#define OLED_RESET -1     // OLED reset pin (if needed)
Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET);

#define MQ2_PIN 26          // MQ-2 sensor analog pin
#define DUST_SENSOR_PIN 34  // Dust sensor analog output pin
#define LED_PIN 25          // LED control for dust sensor

#define ADC_MAX 4095.0      // ESP32 ADC is 12-bit
#define REF_VOLTAGE 3.3     // ESP32 reference voltage

// WiFi & ThingSpeak Settings
const char* ssid = "Hi";  
const char* password = "12345678";  
const char* server = "http://api.thingspeak.com/update";  
String apiKey = "2RM3FD5H6LCOT8CD";  

unsigned long previousMillis = 0;
const long interval = 15000;

void setup() {
    Serial.begin(115200);
    WiFi.begin(ssid, password);

    // Initialize OLED display
    if (!display.begin(SSD1306_SWITCHCAPVCC, 0x3C, OLED_RESET)) {
        Serial.println(F("SSD1306 allocation failed"));
        while (true);
    }
    display.display();  
    delay(2000);  // Pause for 2 seconds to display the startup logo

    // Connect to Wi-Fi
    Serial.print("Connecting to WiFi...");
    int attempts = 0;
    while (WiFi.status() != WL_CONNECTED && attempts < 10) {
        Serial.print(".");
        delay(1000);
        attempts++;
    }

    if (WiFi.status() != WL_CONNECTED) {
        Serial.println("WiFi Connection Failed! Check your credentials.");
        return;
    }
    Serial.println("Connected!");
    
    pinMode(LED_PIN, OUTPUT);
}

int readSensor(int pin) {
    long sum = 0;
    for (int i = 0; i < 10; i++) {
        sum += analogRead(pin);
        delay(10);  
    }
    return sum / 10;  
}

void loop() {
    unsigned long currentMillis = millis();
    if (currentMillis - previousMillis >= interval) {
        previousMillis = currentMillis;

        // Read MQ-2 Gas Sensor
        int gasRaw = readSensor(MQ2_PIN);
        float gasVoltage = gasRaw * (REF_VOLTAGE / ADC_MAX);

        // Read Dust Sensor (GP2Y1010AU0F)
        digitalWrite(LED_PIN, LOW);  // Turn ON LED for stable reading
        delayMicroseconds(280);  
        int dustRaw = readSensor(DUST_SENSOR_PIN);
        delayMicroseconds(40);
        digitalWrite(LED_PIN, HIGH);  // Turn OFF LED
        float dustVoltage = dustRaw * (REF_VOLTAGE / ADC_MAX);
        float dustConcentration = (dustVoltage - 0.1) * 500.0;  // Approximate conversion

        // Print values to Serial Monitor
        Serial.print("MQ-2 Sensor: ");
        Serial.print(gasRaw);
        Serial.print(" | Voltage: ");
        Serial.println(gasVoltage, 3);

        Serial.print("Dust Sensor: ");
        Serial.print(dustRaw);
        Serial.print(" | Voltage: ");
        Serial.print(dustVoltage, 3);
        Serial.print(" | Dust Concentration: ");
        Serial.print(dustConcentration);
        Serial.println(" µg/m3");

        // Display data on OLED
        display.clearDisplay();
        display.setTextSize(1);      
        display.setTextColor(SSD1306_WHITE);  
        display.setCursor(0, 0);    
        display.print("MQ-2 Gas: ");
        display.println(gasVoltage, 3);
        display.print("Dust Conc: ");
        display.println(dustConcentration);
        display.display();

        // Send Data to ThingSpeak
        if (WiFi.status() == WL_CONNECTED) {
            HTTPClient http;
            String url = String(server) + "?api_key=" + apiKey +
                         "&field1=" + String(gasVoltage) +
                         "&field2=" + String(dustConcentration);

            http.begin(url);
            int httpResponseCode = http.GET();
            if (httpResponseCode == 200) {
                Serial.println("Data sent to ThingSpeak");
            } else {
                Serial.print("Failed to send data. HTTP Response Code: ");
                Serial.println(httpResponseCode);
            }
            http.end();
        } else {
            Serial.println("WiFi Disconnected!");
        }
    }
}