Chapter 6: Working with Digital I/O

At the heart of most Arduino projects is the interaction between the board and the outer world, facilitated through its pins. Digital I/O refers to the input and output operations performed on these pins. Let's navigate the realm of digital I/O, which will serve as the foundation for countless interactive projects.

Pin Configuration: Input, Output, PWM

1. Input and Output:
Arduino pins can be configured as either input or output using the pinMode() function.

• OUTPUT: When a pin is set as an output, it can provide a HIGH (usually 5V) or LOW (0V) voltage level.

pinMode(13, OUTPUT);  // Sets digital pin 13 as an output

• INPUT: An input pin reads the voltage level. It can sense HIGH or LOW states from external components.

pinMode(7, INPUT);  // Sets digital pin 7 as an input

2. PWM (Pulse Width Modulation):
Certain digital pins on the Arduino are capable of generating PWM signals, useful for analog-like control, such as dimming LEDs or controlling motors. These pins are usually marked with a "~" symbol.

Reading Switches and Buttons

Switches and buttons serve as user inputs. When interfaced with the Arduino, they allow users to send real-time commands.

Simple Button Read:

int buttonPin = 8;     // Digital pin 8 is connected to the button
int buttonState = 0;   // Variable to store the button's state

void setup() {
  pinMode(buttonPin, INPUT);  // Set the button pin as input
  Serial.begin(9600);        // Begin serial communication
}

void loop() {
  buttonState = digitalRead(buttonPin);  // Read the button's state
  if (buttonState == HIGH) {
    Serial.println("Button Pressed");
  } else {
    Serial.println("Button Released");
  }
  delay(100);  // Short delay for stability
}

Driving LEDs, Buzzers, and Relays

1. LEDs: Light Emitting Diodes are the simplest way to provide visual feedback.

int ledPin = 13;  // LED connected to digital pin 13

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

void loop() {
  digitalWrite(ledPin, HIGH);  // Turn the LED on
  delay(1000);                 // Wait for a second
  digitalWrite(ledPin, LOW);   // Turn the LED off
  delay(1000);                 // Wait for a second
}

2. Buzzers: Buzzers can provide audible feedback. A simple buzzer can be driven similar to an LED. More advanced sound control can be achieved with PWM.

3. Relays: Relays allow your Arduino to control high-power devices, acting as a switch. It's essential to use relays with caution and proper knowledge, especially when interfacing with mains power.

int relayPin = 7;  // Relay connected to digital pin 7

void setup() {
  pinMode(relayPin, OUTPUT);  // Set the relay pin as output
}

void loop() {
  digitalWrite(relayPin, HIGH);  // Turn the relay on
  delay(5000);                   // Wait for 5 seconds
  digitalWrite(relayPin, LOW);   // Turn the relay off
  delay(5000);                   // Wait for 5 seconds
}

Conclusion

Working with digital I/O is fundamental to bringing interactivity to your Arduino projects. Whether you're gathering input through switches, illuminating LEDs, buzzing alarms, or activating large devices using relays, the principles remain consistent. Mastering digital I/O is a pivotal step in your Arduino journey, paving the way for myriad inventive projects.