Print a Button's State

Part of the Inputs section of Coddy's Arduino journey. Lesson 1 of 22.

In Read a Button, digitalRead(pin) gave you HIGH or LOW. To the board these are plain numbers: HIGH is 1 and LOW is 0. So you can keep a reading in an int variable and print it like any other number:

int state = digitalRead(2);
Serial.println(state);

The button here is wired the way you met it before: it joins pin 2 to ground (GND, 0 volts) while you hold it, and INPUT_PULLUP keeps the pin HIGH the rest of the time. So the Serial monitor shows 1 while the button is up and 0 while it is down.

loop() runs thousands of times a second. A short delay(100) after the print keeps the Serial monitor readable: ten lines a second instead of thousands.

Challenge

Easy

The button is on pin 2. Print its state to the Serial monitor:

in setup(), set pin 2 to INPUT_PULLUP
in loop(), read the pin into an int, print it with Serial.println(), then wait 100 ms

Press Run, open the Serial monitor and hold the button, then Check.

Try it yourself

const int buttonPin = 2;

void setup() {
  Serial.begin(9600);
  // set the button pin to INPUT_PULLUP
}

void loop() {
  // read the button, print the reading, wait 100 ms
}

Test yourself

This lesson includes a short quiz. Start the lesson to answer it and track your progress.

All lessons in Inputs

Practice on your own: Arduino playground