Controlling an LED with Two ESP32s: A Step-by-Step Guide

Episode EE03:

Read this blog ALL YOU NEED TO KNOW ABOUT ESP32

What You’ll Need

• LED: For demonstration.
• Resistor: 220Ω to 330Ω to limit the current to the LED.
• Breadboard and Jumper Wires: For connections.
• USB Cables: For programming the ESP32 boards.
• Arduino IDE: For coding and uploading to the ESP32 boards.

Do you know How to connect esp32 to wifi - Read now!

Wi-Fi Communication (Client-Server Model):

Setup ESP32 as a Server (LED Controller)

1. Circuit Diagram

The image shows the LED connected to the ESP32 via a resistor.

• LED Anode (long leg) to GPIO 2 (or any other GPIO) on ESP32.
• LED Cathode (short leg) to GND via a 220Ω resistor.

2. Code for ESP32 Server:

#include 

// Replace with your network credentials
const char* ssid = "YOUR_SSID";
const char* password = "YOUR_PASSWORD";

WiFiServer server(80);

const int ledPin = 2; // LED connected to GPIO 2

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

  while (WiFi.status() != WL_CONNECTED) {
    delay(500);
    Serial.print(".");
  }
  Serial.println("Connected to WiFi");
  server.begin();
  pinMode(ledPin, OUTPUT);
  digitalWrite(ledPin, LOW); // Make sure LED is off initially
}

void loop() {
  WiFiClient client = server.available();
  if (client) {
    String request = client.readStringUntil('\r');
    client.flush();

    if (request.indexOf("/LED_ON") != -1) {
      digitalWrite(ledPin, HIGH);
    }
    if (request.indexOf("/LED_OFF") != -1) {
      digitalWrite(ledPin, LOW);
    }

    client.print("HTTP/1.1 200 OK\r\nContent-Type: text/html\r\n\r\n");
    client.print("\r\n\r\n");
    client.print("\r\n");
    client.print("Turn LED ON\r\n");
    client.print("Turn LED OFF\r\n");
    client.print("\r\n\r\n");
    client.stop();
  }
}

3. Explanation:

The ESP32 server listens for HTTP requests. When it receives a request containing /LED_ON or /LED_OFF, it controls the LED connected to GPIO 2 accordingly.

4. Upload the Code and Test:

• Upload the code to the ESP32 server.
• Open the Serial Monitor to find the IP address of the ESP32.
• Enter the IP address in a web browser. Use the provided links to control the LED.

Learn how to build a Smart water quality monitoring system using ESP32

Setup ESP32 as a Client (Control Sender)

Code for ESP32 Client:

#include 

// Replace with your network credentials and server IP
const char* ssid = "YOUR_SSID";
const char* password = "YOUR_PASSWORD";
const char* serverIP = "SERVER_IP_ADDRESS"; // Replace with the server's IP address

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

  while (WiFi.status() != WL_CONNECTED) {
    delay(500);
    Serial.print(".");
  }
  Serial.println("Connected to WiFi");
}

void loop() {
  WiFiClient client;
  if (client.connect(serverIP, 80)) {
    client.println("GET /LED_ON HTTP/1.1");
    client.println("Host: " + String(serverIP));
    client.println("Connection: close");
    client.println();

    delay(10000); // Wait 10 seconds before sending another request

    client.println("GET /LED_OFF HTTP/1.1");
    client.println("Host: " + String(serverIP));
    client.println("Connection: close");
    client.println();
  }
  delay(10000); // Wait 10 seconds before reconnecting
}

Explanation:

The ESP32 client sends HTTP GET requests to the server to turn the LED on and off periodically.

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Also read: How to interfaceDS18B20 Temperature Sensor with ESP32

Conclusion

Controlling an LED with two ESP32 boards can be achieved using various communication methods, including Wi-Fi and Bluetooth. By following the steps outlined above, you can set up a server-client model over Wi-Fi or use Bluetooth serial communication to control your LED. These methods can be extended to more complex applications and integrated into larger IoT systems. Happy experimenting!

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