Wokwi - Online ESP32, STM32, Arduino Simulator

#include <Wire.h>
#include <LiquidCrystal_I2C.h>
#include <WiFi.h>


LiquidCrystal_I2C lcd(0x27, 16, 2); // LCD I2C

const int mq135Pin = 33; // GPIO33
const int buzzerPin = 25; // GPIO25 for buzzer
WiFiServer server(80);

void setup() {
  Serial.begin(115200);

  lcd.init();
  lcd.backlight();
  lcd.setCursor(0, 0);
  lcd.print("Warming Sensor...");
  delay(2000);

  pinMode(mq135Pin, INPUT);
  pinMode(buzzerPin, OUTPUT);

  //Verify if the WiFi connection is successfully done:
  WiFi.begin("Wokwi-GUEST", "", 6);
  Serial.println("Connecting to WiFi!!");
  while (WiFi.status() != WL_CONNECTED) {
    delay(100);
    Serial.print(".");
  }
  Serial.println("Connected!");
  Serial.print("Local IP: ");
  Serial.println(WiFi.localIP());

  delay(100);
  lcd.clear();
  server.begin();
}

void loop() {
  int analogValue = analogRead(mq135Pin);
  float air_quality = (analogValue / 4095.0) * 5000.0;
 // Basic approximation

  Serial.print("Air Quality: ");
  Serial.print(air_quality);
  Serial.println(" PPM");

  lcd.clear();
  lcd.setCursor(0, 0);
  lcd.print("AQ: ");
  lcd.print(air_quality);
  lcd.print(" PPM");
  lcd.setCursor(0, 1);

  if (air_quality <= 1000) {
    lcd.print("Fresh Air");
    digitalWrite(buzzerPin, LOW);
  } else if (air_quality > 1000 && air_quality <= 2000) {
    lcd.print("Poor, Ventilate!");
    digitalWrite(buzzerPin, HIGH);
  } else {
    lcd.print("DANGER! Go Out!");
    digitalWrite(buzzerPin, HIGH);
  }

  WiFiClient client = server.available();
  if (client) {
    String webpage = "<!DOCTYPE html><html><head><style>";
    webpage += "body{font-family:sans-serif;text-align:center;padding:20px;}";
    webpage += "h1{color:#0066cc;} h2{color:#444;}";
    webpage += "</style></head><body>";
    webpage += "<h1>IoT Air Pollution Monitoring</h1>";
    webpage += "<p><h2>Air Quality: ";
    webpage += air_quality;
    webpage += " PPM</h2></p>";

    if (air_quality <= 1000) {
      webpage += "<p style='color:green;'>Fresh Air</p>";
    } else if (air_quality <= 2000) {
      webpage += "<p style='color:orange;'>Poor Air - Ventilate!</p>";
    } else {
      webpage += "<p style='color:red;'>DANGER! Move Out!</p>";
    }

    webpage += "</body></html>";


    client.print("HTTP/1.1 200 OK\r\n");
    client.print("Content-Type: text/html\r\n");
    client.print("Connection: close\r\n\r\n");
    client.print(webpage);
    client.stop();
  }

  delay(2000);
}