I am using Arduino UNO to read a push button every time it is pressed.Earlier i was simply reading the Digital IO pin to read the count and then i faced the condition of switch debounce regarding which i had asked a question here and get to know that i must use Interrupt instead of reading a digital IO pin but even after using interrupt, i was facing the problem of Switch Debouncing.

So i used this link and code given on this link

const int buttonPin = 2;    // the number of the pushbutton pin
const int ledPin = 13;      // the number of the LED pin

// Variables will change:
int ledState = HIGH;         // the current state of the output pin
int buttonState;             // the current reading from the input pin
int lastButtonState = LOW;   // the previous reading from the input pin

// the following variables are long's because the time, measured in miliseconds,
// will quickly become a bigger number than can be stored in an int.
long lastDebounceTime = 0;  // the last time the output pin was toggled
long debounceDelay = 50;    // the debounce time; increase if the output flickers

void setup() {
  pinMode(buttonPin, INPUT);
  pinMode(ledPin, OUTPUT);

  // set initial LED state
  digitalWrite(ledPin, ledState);

void loop() {
  // read the state of the switch into a local variable:
  int reading = digitalRead(buttonPin);

  // check to see if you just pressed the button
  // (i.e. the input went from LOW to HIGH),  and you've waited
  // long enough since the last press to ignore any noise:  

  // If the switch changed, due to noise or pressing:
  if (reading != lastButtonState) {
    // reset the debouncing timer
    lastDebounceTime = millis();

  if ((millis() - lastDebounceTime) > debounceDelay) {
    // whatever the reading is at, it's been there for longer
    // than the debounce delay, so take it as the actual current state:

    // if the button state has changed:
    if (reading != buttonState) {
      buttonState = reading;

      // only toggle the LED if the new button state is HIGH
      if (buttonState == HIGH) {
        ledState = !ledState;

  // set the LED:
  digitalWrite(ledPin, ledState);

  // save the reading.  Next time through the loop,
  // it'll be the lastButtonState:
  lastButtonState = reading;

and change

 long debounceDelay = 50;

to 10(means read any thing ina time gap of 10 mili second) as the code says.Now what is happening, code is running on the board and after some time my board get hang and LED stop toggling on any press of push button and then i had to manually reset my board.I also want to add upon a thing that i am also using a serial port in between when LED toggles or switch is pressed.

I am totally confused why this is happening.There can beone possibility that this is happening because i reduced time gap between two consecutive events to 10 from 50 miliseconds and that might be making AVR get hanged and thus require a manual reset.

  • $\begingroup$ Have you tried disabling the UART part? Could it be a bug on that part that's causing the AVR to hang? $\endgroup$
    – Shahbaz
    Commented Nov 20, 2013 at 15:22
  • $\begingroup$ In my opinion nothing in the code that you show will cause the microprocessor to "hang". So maybe you should show your complete code? $\endgroup$ Commented Nov 20, 2013 at 23:43
  • $\begingroup$ It get solved automatically and that give me clear hint that when i was using 9v 1 Amp adaptor, because of heat Arduino was getting a type of HANGED..but when i powered it with USB cable..it works fine. $\endgroup$
    – shailendra
    Commented Nov 21, 2013 at 12:23
  • $\begingroup$ @shailendra you should write your latest comment as an answer and accept it so that everybody clearly knows that your problem is fixed already. $\endgroup$
    – jfpoilpret
    Commented Dec 26, 2013 at 9:19
  • $\begingroup$ Also you have not mentioned where into the Arduino you have plugged your 9V supply. Did you directly plug it into the 5V pin? That should be avoided (as there is no regulator behind this pin). $\endgroup$
    – jfpoilpret
    Commented Dec 26, 2013 at 9:24

1 Answer 1


It get solved automatically and that give me clear hint that when i was using 9v 1 Amp adaptor, because of heat Arduino was getting a type of HANGED..but when i powered it with USB cable..it works fine now.


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