What Is the ESP32? Features, Arduino IDE Setup and Your First Wi-Fi Project

The ESP32 is a very cheap, dual-core microcontroller made by Espressif with Wi-Fi and Bluetooth built in. On its own it can do many things an Arduino Uno can't: join your home network, serve a web page you open on your phone, fetch the time and weather from the internet, and talk to your phone over Bluetooth. On top of that, it's programmed in the Arduino IDE with the Arduino commands you already know. Today it's the most popular board for getting started with Internet of Things (IoT) projects.

What is the ESP32 and what is it used for?

Strictly speaking, "ESP32" is the name of the chip under the metal cover. The board you hold is a development board carrying that chip (such as the ESP32 DevKit or NodeMCU-32S): it has a USB-serial converter to talk to your computer, a regulator that drops 5 V to 3.3 V, and reset (EN) and programming (BOOT) buttons. Here are some of the things you can do with an ESP32:

• Wi-Fi weather station: show temperature and humidity on a page you open on your phone.
• Control from your phone: operate a lamp, socket or door with a button on a web page.
• Fetch data from the internet: show the real time (NTP), the weather or exchange rates on a display.
• Send notifications: alert you over Telegram or email when motion is detected.
• Bluetooth devices: build a remote that pairs with your phone, or a device your computer sees as a keyboard.
• Sensors that run for months on batteries: wake up from deep sleep only to take a measurement.

ESP32 vs Arduino Uno

Looking at this table, the ESP32 seems better in every way, but the Uno has its advantages too: because it runs at 5 V it's directly compatible with most older sensors and modules, its pins are tougher, and it holds fewer surprises for beginners. If you don't need wireless, the Uno is still a great place to start; to decide which to pick, take a look at Which Arduino Should I Buy?

ESP32 pins: which ones are safe to use?

The ESP32's pins aren't all "the same" the way they are on an Arduino. Some are connected to the flash memory, some only work as inputs, and the level of others affects how the board boots. You can see your board's full pin map in the Pinout tool; here's a summary:

Setting up the ESP32 in the Arduino IDE

1. In the Arduino IDE open File > Preferences and add https://espressif.github.io/arduino-esp32/package_esp32_index.json to the "Additional boards manager URLs" field.
2. In the Boards Manager, search for esp32 and install the package by Espressif Systems.
3. Choose ESP32 Dev Module from Tools > Board.
4. Connect the ESP32 with a USB cable and pick the right port from Tools > Port. If no port appears, install the driver for your board's USB-serial chip (CP2102 or CH340).
5. If "Connecting..." stays on screen for a long time while uploading, hold down the BOOT button on the board and release it once the upload starts.

First program: blinking the built-in LED

Most ESP32 DevKit boards have a blue LED connected to GPIO 2. The code below blinks it every half second; as you can see, the commands are exactly the same as on Arduino:

1const int LED_PIN = 2;   // çoğu DevKit'te dahili mavi LED / onboard blue LED on most DevKits
2
3void setup() {
4  pinMode(LED_PIN, OUTPUT);
5}
6
7void loop() {
8  digitalWrite(LED_PIN, HIGH);
9  delay(500);
10  digitalWrite(LED_PIN, LOW);
11  delay(500);
12}

Connecting to Wi-Fi

The ESP32's real strength is Wi-Fi. The code below joins your home network and prints the IP address your router gives the ESP32 to the Serial Monitor. Replace the network name and password with your own and open the Serial Monitor at 115200 baud:

1#include <WiFi.h>
2
3const char* ssid = "AgAdi";        // Wi-Fi adın / your Wi-Fi name
4const char* password = "Sifre123"; // Wi-Fi şifren / your Wi-Fi password
5
6void setup() {
7  Serial.begin(115200);
8  WiFi.begin(ssid, password);
9  Serial.print("Bağlanıyor / connecting");
10  while (WiFi.status() != WL_CONNECTED) {
11    delay(500);
12    Serial.print(".");
13  }
14  Serial.println();
15  Serial.print("IP adresi / IP address: ");
16  Serial.println(WiFi.localIP());
17}
18
19void loop() {
20}

Controlling an LED from your phone: a simple web server

Now let's turn the ESP32 into a small web server. After uploading, open the IP address shown in the Serial Monitor in the browser of a phone on the same Wi-Fi; the two buttons on the page switch the board's LED on and off. Connect a relay instead of the LED and you can control a real lamp the same way; see What Is a Relay Module?

1#include <WiFi.h>
2#include <WebServer.h>
3
4const char* ssid = "AgAdi";
5const char* password = "Sifre123";
6const int LED_PIN = 2;
7
8WebServer server(80);
9
10void handleRoot() {
11  server.send(200, "text/html",
12    "<meta name='viewport' content='width=device-width'>"
13    "<h1>ESP32</h1>"
14    "<a href='/on'><button>LED AÇ / ON</button></a> "
15    "<a href='/off'><button>LED KAPAT / OFF</button></a>");
16}
17
18void setup() {
19  pinMode(LED_PIN, OUTPUT);
20  Serial.begin(115200);
21  WiFi.begin(ssid, password);
22  while (WiFi.status() != WL_CONNECTED) delay(500);
23  Serial.println(WiFi.localIP());   // bu adresi telefonda aç / open this address on your phone
24
25  server.on("/", handleRoot);
26  server.on("/on",  []() { digitalWrite(LED_PIN, HIGH); handleRoot(); });
27  server.on("/off", []() { digitalWrite(LED_PIN, LOW);  handleRoot(); });
28  server.begin();
29}
30
31void loop() {
32  server.handleClient();
33}

ESP32 variants: which one should you buy?

Power supply and running on batteries

When it switches Wi-Fi on, the ESP32 can briefly draw up to 250 mA. If a weak USB port or a thin cable can't handle this sudden load, the board restarts with the message "Brownout detector was triggered". Use a good cable and a 5 V adapter that supplies at least 1 A; if needed, add a 100–470 µF capacitor between 3V3 and GND. For battery projects, the ESP32's deep sleep mode cuts the chip's consumption to microamps; however, the regulator and LED on development boards keep drawing a few mA, so for long battery life a bare module or a low-power board is preferred.

The ESP32 with MicroPython

The ESP32 can be programmed not only in the Arduino language but also in MicroPython. Once you've flashed MicroPython to the board with Thonny, connecting to Wi-Fi takes just a few lines:

1import network, time
2from machine import Pin
3
4led = Pin(2, Pin.OUT)
5wlan = network.WLAN(network.STA_IF)
6wlan.active(True)
7wlan.connect("AgAdi", "Sifre123")     # Wi-Fi adı ve şifresi / Wi-Fi name and password
8
9while not wlan.isconnected():
10    time.sleep(0.5)
11print("IP:", wlan.ifconfig()[0])
12
13while True:
14    led.value(not led.value())        # LED'i yakıp söndür / toggle the LED
15    time.sleep(0.5)

ESP32 project ideas

• Wi-Fi weather station: monitor the temperature and humidity measured by a DHT11 from your phone.
• Smart socket: switch on a lamp with a relay from a web page or a voice assistant.
• Motion alarm: send a Telegram notification when a PIR sensor detects someone.
• Internet clock: get the time from an NTP server and show it on an LCD or 7-segment display.
• Bluetooth remote: drive a robot car with an app on your phone.
• Battery-friendly sensor: build a device that wakes up every 10 minutes, sends a reading and goes back to sleep.

Common mistakes and how to fix them

• No port appears: the cable may be charge-only, or the USB-serial driver isn't installed; use a data cable and install the CP2102 or CH340 driver.
• "Failed to connect... Timed out waiting for packet header": hold the BOOT button while the upload starts.
• The board keeps restarting: not enough power (brownout); use a better cable, adapter and a capacitor.
• It won't connect to Wi-Fi: the network may be 5 GHz, or there's a capitalisation mistake in the name or password.
• Using GPIO 6–11: these pins are connected to the flash; using them crashes the board.
• Analog values go wrong when Wi-Fi starts: the sensor is on an ADC2 pin; move it to one of the ADC1 pins between GPIO 32 and 39.

The ESP32 is the easiest way to take what you've learned on Arduino onto the internet. To brush up on Arduino basics, see What Is Arduino?; in the BlueGrays app you'll find dozens of ESP32 projects, including LEDs, web servers, WebSockets, an NTP clock, weather data and a Telegram alarm, with circuit diagrams and code.