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

Experiment 1: Introduction to ESP32and 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 features Wi-Fi and Bluetooth (Classic + BLE) connectivity, making it ideal for IoT (Internet of Things) applications.

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

⚙️ Key Features

Dual-core 32-bit processor (Xtensa LX6) running up to 240 MHz

Integrated Wi-Fi (802.11 b/g/n) and Bluetooth 4.2 / BLE

Up to 520 KB SRAM and external flash support

Multiple peripherals: ADC, DAC, UART, SPI, I2C, PWM, Touch sensors

Ultra-low-power modes for battery-powered applications

On-chip hall sensor and temperature sensor

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 Diagram

Board 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
}

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.