GPIO Mastery (Digital & Analog)

GPIO Mastery (Digital & Analog)

Objective: Learn how to send signals (Output) and receive information (Input) using both Digital and Analog methods.

Presentation:

Esp32_4_Digital Input & Output by Infinite Engineers

1. Digital I/O (Input/Output)

Digital signals are binary—they are either HIGH (3.3V) or LOW (0V).

• Digital Output: Used to turn things on or off, like an LED or a Buzzer.
  • Function: digitalWrite(pin, HIGH);
• Digital Input: Used to check the state of a device that has only two conditions, like a Push Button or an IR Sensor.
  • Function: digitalRead(pin);

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2. Analog I/O (Input/Output)

Presentation:

Esp32_6_Analog Input by Infinite Engineers Esp32_6_Analog Input by Infinite Engineers

The real world isn’t just ON or OFF; it has ranges (like the brightness of a light or the speed of a motor).

• Analog Input (ADC): The ESP32 converts incoming voltage (0V to 3.3V) into a number between 0 and 4095.
  • Components: LDR (Light Sensor) or Potentiometer.
  • Function: analogRead(pin);
• Analog Output (PWM): The ESP32 uses Pulse Width Modulation (PWM) to “fake” an analog voltage by pulsing a digital signal very fast. This is how we dim an LED or control motor speed.
  • Function: ledcWrite(channel, value); (Note: ESP32 uses ledc functions for PWM instead of the standard analogWrite).

3. Hands-on Experiment:

Project 1: The Toggle Switch (Digital I/O)

In this project, the student will use the pushbutton to toggle the state of an LED.

• Logic: If the button is pressed (Input), change the LED state (Output) from OFF to ON, or vice versa.
• Hardware: Use the ESP32 , a 4-pin switch , and an LED.
• Wiring:
  • Connect the Switch to Pin 4 (Input).
  • Connect the LED to Pin 2 (Output).

The Code Snippet:

const int buttonPin = 4;
const int ledPin = 2;
bool ledState = LOW;

void setup() {
  pinMode(buttonPin, INPUT_PULLUP); // Internal resistor keeps it HIGH until pressed
  pinMode(ledPin, OUTPUT);
}

void loop() {
  if (digitalRead(buttonPin) == LOW) { // Button pressed
    ledState = !ledState;              // Toggle logic
    digitalWrite(ledPin, ledState);
    delay(200);                        // Debounce delay
  }
}

Project 2: Breathing LED (PWM Output)

This project teaches students how to create a “breathing” effect (fading in and out) using Pulse Width Modulation (PWM). This is the foundation for controlling motor speeds later in the day.

• Concept: Instead of just HIGH or LOW, we vary the Duty Cycle to change the average voltage the LED receives.
• Hardware: ESP32 , LED , and a 1K Resistor.

The Code Snippet:

const int ledPin = 2;
int brightness = 0;
int fadeAmount = 5;

void setup() {
  // ESP32 uses ledc for PWM
  ledcAttach(ledPin, 5000, 8); // Pin, Frequency (5kHz), Resolution (8-bit: 0-255)
}

void loop() {
  ledcWrite(ledPin, brightness); 
  brightness = brightness + fadeAmount;

  if (brightness <= 0 || brightness >= 255) {
    fadeAmount = -fadeAmount; // Reverse the fading direction
  }
  delay(30);
}

Required Things for these Projects

• ESP32 / Esp8266 30 pin board
• USB Cable
• Breadboard
• LED (Assorted)
• 4-pin Switch
• 1K Ohm Resistor
• Jumper Wires (M to M)