Arduino digitalread() Digital Input Tutorial

This is a comprehensive guide for Arduino digitalRead in which you’ll learn about Arduino digital input pins and how to configure the pinMode and read the digital state of an Arduino digital input pin. We’ll create a couple of Arduino digital input example projects to practice what we’re going to learn.

We’ll also investigate the digitalRead function’s speed to find out its execution time. And finally, we’ll discuss how to use the Arduino analog input pins as digital input pins. Without further ado, let’s get right into it!

Arduino Digital Input Pins
Arduino pinMode() Function
Arduino digitalRead Function
Arduino digitalRead Examples
Arduino digitalRead Speed

Arduino digitalRead Analog Pins
Arduino digitalRead Always High
Arduino digitalRead Wrap Up

Arduino Digital Input Pins

The Arduino GPIO (digital IO) pins can be configured as digital input pins to be used for reading digital inputs (like push buttons, sensors, etc). In order to configure a digital IO pin as an input, we need to use the pinMode() function. Let’s say we want to configure Arduino’s pin number 2 to be an input pin. Here is how to do it in code.

1	pinMode(2, INPUT);

And now, we can use the Arduino digitalRead() function to get the pin state ( HIGH or LOW).

1	pinState = digitalRead(2);

After executing the line of code above, the variable pinState will have the digital state (HIGH or LOW) of the IO pin2 stored in it. You can then do a conditional check, print it, or whatever you need in your application.

Arduino pinMode() Function

The Arduino pinMode() function sets the behavior of a specific digital IO pin to behave as an output pin or an input pin. It can also enable the internal pull-up resistor for input pins if the mode INPUT_PULLUP is selected. However, the mode INPUT will set your IO pin in input mode and explicitly disable the internal pull-up resistor.

The Arduino pinMode() function takes only 2 parameters:

pin: the Arduino pin number to be configured.
mode: it can be( INPUT, OUTPUT, or INPUT_PULLUP).

For example, to set pin number 2 to be an input pin. Here is how to do it:

1	pinMode(2, INPUT);

And if we need to set the Arduino pin number 2 to be an input pin with the internal pull-up resistor enabled, we can use the INPUT_PULLUP mode as shown below.

1	pinMode(2, INPUT_PULLUP);

To learn more about the Arduino pinMode() function, INPUT_PULLUP, INPUT_PULLDOWN modes, pin floating state, and how to implement internal or external pull-up, it’s highly recommended that you check out the tutorial linked below.

???? Also Read

Arduino pinMode Function & Arduino INPUT_PULLUP Explained

Arduino pinMode Function & INPUT_PULLUP / PULLDOWN

This article will give more in-depth information about the Arduino pinMode() function, INPUT_PULLUP, INPUT_PULLDOWN modes, pin floating state, and how to implement internal or external pull-up

Arduino digitalRead Function

The Arduino digitalRead() function reads the digital state of an input pin ( HIGH or LOW) and return it.

Syntax

1	digitalRead(pin);

Parameters

pin: the Arduino pin number you want to read

Return

HIGH or LOW (1 or 0)

Example Code

#define BTN_PIN 4

void setup()

{

pinMode(LED_BUILTIN, OUTPUT);

pinMode(BTN_PIN, INPUT);

}

void loop()

{

while(digitalRead(BTN_PIN))

{

digitalWrite(LED_BUILTIN, HIGH);

}

digitalWrite(LED_BUILTIN, LOW);

}

❕ Note

Leaving an input pin in a floating state can result in the digitalRead() function returning always HIGH, always LOW, or even a randomly changing value HIGH or LOW. Check the Arduino pinMode Tutorial for more information on this.

Arduino digitalRead Examples

Now, let’s test what we’ve learned so far about the Arduino digitalRead function and create a couple of example projects. In the first example, we’ll read the digital state of a pin hooked to a push button and use it to control an LED on an output pin. Next, we’ll read the state of a push button to toggle the LED on and off with every button click.

1. Arduino Button + LED Example

What we’ll implement is called a “momentary button action” in which the LED will turn ON as long the button is held down and it’ll go OFF whenever the button is released. The button will be connected to Arduino’s IO pin 4, and the LED will stay on the same pin 13.

Wiring

Here is how to hook up the external LED output. (note that the LED current limiting resistor is 330Ω). The push button here is connected in a pull-down configuration with a pull-down resistor of 10kΩ.

Example Code

Here is the full code listing for this example.

* LAB Name: Arduino LED+Button

* Author: Khaled Magdy

* For More Info Visit: www.DeepBlueMbedded.com

#define BTN_PIN 4

void setup()

{

pinMode(LED_BUILTIN, OUTPUT);

pinMode(BTN_PIN, INPUT);

}

void loop()

{

while(digitalRead(BTN_PIN))

{

digitalWrite(LED_BUILTIN, HIGH);

}

digitalWrite(LED_BUILTIN, LOW);

}

Code Explanation

The code example simply set the Builtin-LED IO pin to be output and defines BTN_PIN to be IO pin4 and sets it as an input pin. Then we read the digital state of the Button pin and turn on the LED while the button is pressed, when the button is released, the LED will be driven low again.

This is the button pin definition (assignation)

1	#define BTN_PIN 4

setup()

in the setup() function, we initialize the digital IO pin ( LED_BUILTIN or pin 13) to be an OUTPUT pin. And the BTN_PIN to be an input pin.

loop()

in the loop() function, we continuously read the state of the button’s pin. While it’s held down (state=1), the LED will be turned ON. When the button is released, the while loop condition breaks and the LED will be driven back to the LOW state.

Simulation

Here is the simulation result for this project on the TinkerCAD simulator.

You can check this simulation project on TinkerCAD using this link.

Testing Results

Here is a demo video for testing this project on my Arduino UNO board.