Experiment 1: Introduction to ESP32 and Digital I/O Control

Objective

To understand digital input/output operations by interfacing LEDs and push buttons with ESP32.

Introduction to ESP32

The ESP32 is a low-cost, low-power system-on-chip (SoC) developed by Espressif Systems. It includes both Wi-Fi and Bluetooth (Classic + BLE) connectivity, making it ideal for various IoT (Internet of Things) applications.

It is the successor to the popular ESP8266, offering higher performance, more GPIO pins, and advanced features such as dual-core processing and hardware encryption.

Key Features

Dual-core 32-bit processor (Xtensa LX6) up to 240 MHz
Integrated Wi-Fi (802.11 b/g/n) and Bluetooth 4.2 / BLE
Up to 520 KB SRAM with external flash support
Multiple peripherals: ADC, DAC, UART, SPI, I²C, PWM, Touch sensors
Ultra-low-power modes for battery-powered projects
On-chip Hall sensor and temperature sensor

Common Applications

IoT devices and smart home automation
Wireless sensor networks
Data logging and remote monitoring
Robotics and industrial control
Wearable and Bluetooth-based projects

Task

Connect LEDs and push buttons to ESP32.
Write a program to turn LEDs ON/OFF based on button press.
Observe the response on the Serial Monitor.

⚠️ Disconnect your ESP32 from the computer while making or removing component connections.

Circuit & Board Connections

   
   
Circuit Diagram

   The complete connection diagram of ESP32-based setup.

   
   
Board Connections

   Actual board wiring layout showing sensor and module connections.

Circuit Connections

Push Button	ESP32 Pin
Push Button 1	12
Push Button 2	13
Push Button 3	14
Push Button 4	15
Push Button GND	GND
Push Button VCC	3.3 V / Vin

LED Bar	ESP32 Pin
LED 1	21
LED 2	22
LED 3	25
LED 4	26
LED GND	GND

Serial Communication: 9600 baud rate

ESP32 Code

// © 2025, Cognifront. Member of The IoT Kits Family.
// Experiment 1: Introduction to Arduino/ESP32 and Digital I/O Control

// Define push button input pins
int push1Pin = 12;
int push2Pin = 13;
int push3Pin = 14;
int push4Pin = 15;

// Variables to store button states
int push1Value;
int push2Value;
int push3Value;
int push4Value;

// Define LED output pins
int ledPin1 = 21;
int ledPin2 = 22;
int ledPin3 = 25;
int ledPin4 = 26;

void setup() {
  // Start serial communication for debugging
  Serial.begin(9600);

  // Set push button pins as INPUT with internal pull-down or pull-up as needed
  pinMode(push1Pin, INPUT);
  pinMode(push2Pin, INPUT);
  pinMode(push3Pin, INPUT);
  pinMode(push4Pin, INPUT);

  // Set LED pins as OUTPUT
  pinMode(ledPin1, OUTPUT);
  pinMode(ledPin2, OUTPUT);
  pinMode(ledPin3, OUTPUT);
  pinMode(ledPin4, OUTPUT);

  Serial.println("System Initialized: Monitoring Push Buttons and LEDs...");
}

void loop() {
  // Read button states (LOW = pressed when using INPUT_PULLUP)
  push1Value = digitalRead(push1Pin);
  push2Value = digitalRead(push2Pin);
  push3Value = digitalRead(push3Pin);
  push4Value = digitalRead(push4Pin);

  // Control LEDs based on button pressed
  if (push1Value == HIGH) {
    digitalWrite(ledPin1, HIGH);
    digitalWrite(ledPin2, LOW);
    digitalWrite(ledPin3, LOW);
    digitalWrite(ledPin4, LOW);
    Serial.println("Button1 PRESSED → LED1 ON");
  }
  else if (push2Value == HIGH) {
    digitalWrite(ledPin1, LOW);
    digitalWrite(ledPin2, HIGH);
    digitalWrite(ledPin3, LOW);
    digitalWrite(ledPin4, LOW);
    Serial.println("Button2 PRESSED → LED2 ON");
  }
  else if (push3Value == HIGH) {
    digitalWrite(ledPin1, LOW);
    digitalWrite(ledPin2, LOW);
    digitalWrite(ledPin3, HIGH);
    digitalWrite(ledPin4, LOW);
    Serial.println("Button3 PRESSED → LED3 ON");
  }
  else if (push4Value == HIGH) {
    digitalWrite(ledPin1, LOW);
    digitalWrite(ledPin2, LOW);
    digitalWrite(ledPin3, LOW);
    digitalWrite(ledPin4, HIGH);
    Serial.println("Button4 PRESSED → LED4 ON");
  }
  else {
    // If no button is pressed, turn off all LEDs
    digitalWrite(ledPin1, LOW);
    digitalWrite(ledPin2, LOW);
    digitalWrite(ledPin3, LOW);
    digitalWrite(ledPin4, LOW);
    Serial.println("No button pressed → All LEDs OFF");
  }

  // Print raw button states
  Serial.print("Buttons: ");
  Serial.print(push1Value);
  Serial.print(" ");
  Serial.print(push2Value);
  Serial.print(" ");
  Serial.print(push3Value);
  Serial.print(" ");
  Serial.println(push4Value);

  delay(300); // Small delay for readability
}

 ⬇ Click Here to Download Code File
 

 (Contains ESP32 source code)
 

 
 

 Connect your ESP32 to your computer and upload the code.

Observation

Pressing any button will turn ON the corresponding LED.
Only one LED lights up at a time because of the else-if structure.
Serial Monitor can be used to confirm button press readings.

Conclusion

This experiment demonstrates basic digital input and output control using ESP32.

Real Life Examples

Automated Assembly Line Control: Digital I/O is used to operate actuators, solenoids, and indicator lamps. For example, pressing a start button activates a conveyor motor, demonstrating machine automation control in manufacturing lines.