131- ESP32 - Wokwi ESP32, STM32, Arduino Simulator

// ESP32 mDNS + Web Server + I2C LCD
// LED: GPIO 5 (220 ohm) | LCD: SDA=21 SCL=22 VCC=VIN

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

const char* WIFI_SSID     = "Wokwi-GUEST";
const char* WIFI_PASS     = "";
const char* MDNS_HOSTNAME = "bluegrays-esp";

#define LED_PIN  5
#define I2C_SDA 21
#define I2C_SCL 22

LiquidCrystal_I2C lcd(0x27, 16, 2);
WebServer server(80);

bool   ledState = false;
String currentIP = "0.0.0.0";
bool   wifiOk = false;

// Sahte istemciler (sunum icin) / Fake clients
const char* clients[] = {
  "iPhone-Emre",
  "Macbook-Pro",
  "iPad-Mini"
};
const uint8_t clientCount = 3;

void lcdLine(uint8_t row, const String &text) {
  lcd.setCursor(0, row);
  String t = text;
  while (t.length() < 16) t += " ";
  lcd.print(t.substring(0, 16));
}

void showIdle() {
  lcdLine(0, String(MDNS_HOSTNAME) + ".lo");
  lcdLine(1, "IP:" + currentIP);
}

// Istemci baglantisi simulasyonu / Client request simulation
void handleClientAction(bool on, const char* client) {
  // 1) Cihaz baglandi / Device connected
  lcdLine(0, client);
  lcdLine(1, on ? "-> AC istegi" : "-> KAPAT istegi");
  delay(2000);

  // 2) Islendi / Processed
  ledState = on;
  digitalWrite(LED_PIN, on ? HIGH : LOW);
  lcdLine(0, String(MDNS_HOSTNAME) + ".lo");
  lcdLine(1, on ? "LED: ACIK   OK" : "LED: KAPALI OK");
  delay(2500);
}

String htmlPage() {
  String h = "<!DOCTYPE html><html><head><meta charset='UTF-8'>";
  h += "<title>BlueGrays mDNS</title></head><body style='font-family:Arial;text-align:center;padding:30px'>";
  h += "<h1>BlueGrays mDNS</h1>";
  h += "<p>URL: http://"; h += MDNS_HOSTNAME; h += ".local/</p>";
  h += "<p>IP: "; h += currentIP; h += "</p>";
  h += "<p>LED: <b>"; h += (ledState ? "ACIK" : "KAPALI"); h += "</b></p>";
  h += "<p><a href='/on'>AC</a> | <a href='/off'>KAPAT</a></p>";
  h += "</body></html>";
  return h;
}

void handleRoot() { server.send(200, "text/html; charset=utf-8", htmlPage()); }
void handleOn()   { ledState = true;  digitalWrite(LED_PIN, HIGH); server.sendHeader("Location","/"); server.send(303); }
void handleOff()  { ledState = false; digitalWrite(LED_PIN, LOW);  server.sendHeader("Location","/"); server.send(303); }

void setup() {
  pinMode(LED_PIN, OUTPUT);
  digitalWrite(LED_PIN, LOW);

  // LCD ilk basta hazirla / Init LCD first
  Wire.begin(I2C_SDA, I2C_SCL);
  lcd.init();
  lcd.backlight();

  // Splash 3sn / Splash 3s
  lcdLine(0, "   BlueGrays");
  lcdLine(1, "   mDNS v1.0");
  delay(3000);

  // WiFi baglanti — 20sn timeout / WiFi — 20s timeout
  lcdLine(0, "WiFi baglaniyor");
  lcdLine(1, "Connecting...");
  WiFi.mode(WIFI_STA);
  WiFi.begin(WIFI_SSID, WIFI_PASS);

  unsigned long startWifi = millis();
  while (WiFi.status() != WL_CONNECTED && millis() - startWifi < 20000) {
    delay(400);
  }

  if (WiFi.status() == WL_CONNECTED) {
    wifiOk = true;
    currentIP = WiFi.localIP().toString();
    lcdLine(0, "WiFi baglandi");
    lcdLine(1, currentIP);
    delay(2500);

    if (MDNS.begin(MDNS_HOSTNAME)) {
      MDNS.addService("http", "tcp", 80);
      lcdLine(0, "mDNS baslatildi");
      lcdLine(1, String(MDNS_HOSTNAME) + ".lo");
      delay(2500);
    }

    server.on("/", handleRoot);
    server.on("/on", handleOn);
    server.on("/off", handleOff);
    server.begin();
  } else {
    // WiFi yok — offline calismaya devam / WiFi failed — offline
    currentIP = "10.0.0.42";
    lcdLine(0, "WiFi baglanmadi");
    lcdLine(1, "Offline calisma");
    delay(2500);
  }

  showIdle();
  delay(2000);
}

void loop() {
  if (wifiOk) server.handleClient();

  // 4sn'de bir farkli cihaz baglaniyor / Every 4s another client
  static unsigned long lastAction = 0;
  static uint8_t step = 0;
  if (millis() - lastAction > 4000) {
    lastAction = millis();
    const char* who = clients[step % clientCount];
    bool on = (step % 2 == 0);
    handleClientAction(on, who);
    showIdle();
    step++;
  }
  delay(2);
}