So for my project, I am making a button that turns on and off an LED, but also display the state of the led on an LCD and by Serial. But my issue is, I don't want it to just show a 0 or a 1, I want it to say On or Off.

#include <LiquidCrystal.h>
LiquidCrystal lcd(12, 11, 5, 4, 3, 2);

int inPin = 22;         // the number of the input pin
int outPin = 13;       // the number of the output pin

int state = HIGH;      // the current state of the output pin
int reading;           // the current reading from the input pin
int previous = LOW;    // the previous reading from the input pin

// the follow variables are long's because the time, measured in miliseconds,
// will quickly become a bigger number than can be stored in an int.
long time = 0;         // the last time the output pin was toggled
long debounce = 200;   // the debounce time, increase if the output flickers

void setup(){
    // set up the LCD's number of columns and rows:
    lcd.begin(16, 2);
    // Print a message to the LCD.
    lcd.print("System Activated");
    lcd.setCursor(0, 1);

    pinMode(inPin, INPUT);
    pinMode(outPin, OUTPUT);

    Serial.println("System Activated");
    Serial.println("Made by Mateo Holguin");
    Serial.println("0 = Light is Off | 1 = Light is On");

void loop(){
    reading = digitalRead(inPin);

    if (reading == HIGH && previous == LOW && millis() - time > debounce) {
        Serial.println("Button Switch State Change:");
        if (state == HIGH)
            state = LOW;
            state = HIGH;

        lcd.print("State: ");

        time = millis();    

    digitalWrite(outPin, state);

    previous = reading;
  • Both of these 2 answers works well, I just used the second one as I am a bit of a noob so I used one that I can understand more. – Mateo Holguin Nov 14 '15 at 20:43

Another option: use the "inline" if construct:

lcd.print(state ? F("On") : F("Off"));

The format is:

<if comparison> ? <true result> : <false result>

Note the use of F(...) to force the strings to stay in flash memory.

  • I am going to try this option as well, as it makes a lot of sense to me. Thank you very much! – Mateo Holguin Nov 11 '15 at 16:19
  • When I use that line I get " '_F' was not declared in this scope" – Mateo Holguin Nov 14 '15 at 20:40
  • @MateoHolguin Sorry, wasn't thinking straight that day - it's F() not _F() – Majenko Nov 14 '15 at 20:41
  • I uploaded it to the Arduino, and it works perfectly the way I needed it to! Thanks again – Mateo Holguin Nov 14 '15 at 20:42

Put the strings to display in an array, and output them instead.

char const * const stateDisplay[] = {"Off", "On"};


  • Could you please explain why "const" is used twice there? I've never seen that before and don't know how to look it up. – Jerry Nov 10 '15 at 10:04
  • 1
    @Jerry: One is for stateDisplay (i.e. the pointer is constant), and the other is for *stateDisplay (i.e. the contents are constant as well). – Ignacio Vazquez-Abrams Nov 10 '15 at 10:06
  • Thanks! I can actually use that in a sketch I'm working on now. – Jerry Nov 10 '15 at 10:14
  • Thank you very much! I can finally get that one issue fixed! – Mateo Holguin Nov 11 '15 at 16:15

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