LED Blinking with ESP32 DOIT DevKit v1 – Step-by-Step Tutorial

Introduction

The LED blink program is often called the “Hello World” of embedded systems. It’s the simplest way to test if your ESP32 is working properly and if you can control an output device.

In this tutorial, we will blink an external LED connected to GPIO 12 of the ESP32 DOIT DevKit v1. This will help you understand:

• How to use GPIO pins as outputs.
• How to control an LED using Arduino code.
• The basics of digitalWrite() and pinMode().

Components Required

• ESP32 DOIT DevKit v1
• 1 × LED (any color)
• 1 × Resistor (220Ω – 330Ω recommended)
• Breadboard and jumper wires
• USB cable

Circuit Diagram

• Connect LED anode (+, long leg) → GPIO 12 via a 220Ω resistor
• Connect LED cathode (-, short leg) → GND

⚡ Note: We use GPIO 12 because we already fixed it in our series pin mapping.

Arduino Code

// LED Blinking with ESP32 DOIT DevKit v1
int ledPin = 12;  // LED connected to GPIO 12

void setup() {
  pinMode(ledPin, OUTPUT);  // Set pin as OUTPUT
}

void loop() {
  digitalWrite(ledPin, HIGH);  // Turn LED ON
  delay(1000);                 // Wait 1 second
  digitalWrite(ledPin, LOW);   // Turn LED OFF
  delay(1000);                 // Wait 1 second
}

Step-by-Step Code Explanation

1. Define LED Pin

int ledPin = 12;

We assign GPIO 12 to ledPin since our external LED is connected there.

Setup Function

pinMode(ledPin, OUTPUT);

This tells ESP32 that GPIO 12 will be used as an output pin.

Loop Function

digitalWrite(ledPin, HIGH);
delay(1000);
digitalWrite(ledPin, LOW);
delay(1000);

Turn LED ON → Wait 1 second

Turn LED OFF → Wait 1 second

Repeat forever

Output

• The LED will turn ON for 1 second and then turn OFF for 1 second, repeatedly.
• You can try changing the delay values to make the LED blink faster or slower.

Real-Life Applications

• Status Indicators (Power ON, Wi-Fi Connected, Error States).
• Debugging (use blink patterns to show sensor readings or system states).
• Notifications (blink LED when a message is received or sensor detects something).

Troubleshooting

Problem	Cause	Solution
LED not blinking	Wrong wiring	Check LED polarity and resistor connection
Upload error	Wrong board/port selected	Select “DOIT ESP32 DEVKIT V1” in Arduino IDE
LED stays always ON	Pin set incorrectly	Double-check LED pin (GPIO 12)
Dim LED	No resistor / high resistor	Use 220Ω – 330Ω resistor for brightness