Arduino: How to use Digital Pin as a Digital Input with Serial Monitor

Working with digital pins is one of the most fundamental skills when learning Arduino. In this tutorial, we will explore how to configure digital pin 7 as an input, read its state, and display the result on the Serial Monitor. This is a great starting point for beginners who want to understand how buttons, switches, or sensors interact with Arduino.

 

What You’ll Need

·       Arduino Uno

·       USB cable

·       Push button or switch

·       Breadboard and jumper wires

·       Resistor (10kΩ recommended for pull-down setup)

 

Understanding Digital Input

Digital pins on Arduino can be configured as either INPUT or OUTPUT.

·       INPUT mode allows the pin to detect voltage levels (HIGH or LOW).

·       A HIGH signal means the pin is receiving ~5V (on most Arduino boards).

·       A LOW signal means the pin is at 0V (ground).

We’ll use pin 7 as an input to detect whether a button is pressed or not.

 

Circuit Setup

·       Connect one side of the push button or any switch to pin 7.

·       Connect the other side of the button/switch to 5V.

·       Add a 10kΩ resistor between pin 7 and GND (this acts as a pull-down resistor, ensuring the pin reads LOW when the button isn’t pressed).

 

This way:

·       Button pressed → pin 7 reads HIGH.

·       Button released → pin 7 reads LOW.

Arduino Code

// Digital Input Example using Pin 7

const int buttonPin = 7;   // Pin 7 as input

int buttonState = 0;       // Variable to store state

 

void setup() {

  // Initialize pin 7 as input

  pinMode(buttonPin, INPUT);

 

  // Start Serial communication at 9600 baud

  Serial.begin(9600);

}

 

void loop() {

  // Read the state of pin 7 using digitalRead() function

  buttonState = digitalRead(buttonPin);

 

  // Print the state to Serial Monitor

  if (buttonState == HIGH) {

    Serial.println("Button is PRESSED");

  } else {

    Serial.println("Button is RELEASED");

  }

 

  delay(500); // Small delay for readability

}

Viewing Results on Serial Monitor

1.     Upload the code to your Arduino board.

2.     Open the Serial Monitor (Tools → Serial Monitor or press Ctrl+Shift+M).

3.     Set the baud rate to 9600.

4.     Press and release the button — you’ll see messages like:

·       Button is PRESSED: When button is pressed

·       Button is RELEASED: When button is released

 

Applications

Once you understand digital inputs and its working, you can expand this concept to:

·       Detect motion using PIR sensors

·       Read toggle switches for controlling devices

·       Build interactive projects with multiple buttons

·       And so on…

 

Conclusion

Using digital pins as inputs is a cornerstone of Arduino programming. With just a button, a resistor, and a few lines of code, you can start building interactive projects.

Pin 7 is just one example — but the same logic can be applied to any digital pin.