Where am I wrong?Debounce related question[SOLVED]

Hi all, I’m having a problem that’s really driving me crazy!

I just take the debounce code from the Arduino examples sketch, and I add only a couple of check more:

void loop() {
  int reading = digitalRead(buttonPin);

  // 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:
    buttonState = reading;
    
[glow]      if(buttonState == HIGH)
    {
      if(toggle == HIGH)
        toggle = LOW;
      else
        toggle = HIGH;
    }[/glow]
  }
  
  // set the LED using the state of the toggle:
  [glow]digitalWrite(ledPin, toggle);       [/glow]                   

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

the highlighted part is mine, what I need is this behaviour:

  • button is pressed and led is off ? Switch on the led
  • button is pressed and led is on ? Switch off the led

but the problem is that it randomly works, sometime it needs 2 or 3 presses to switch on/off the led, sometime it does that on the first press.

Do you see something wrong in my code?

ok, I found part of the problem, I needed to change the "toggle" only if buttonState was changed, but now it happens that the led is never switched on :-(

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: buttonState = reading;

if (buttonState == LOW && lastButtonState == HIGH || buttonState == HIGH && lastButtonState == LOW) { if(toggle == HIGH) toggle = LOW; else toggle = HIGH; } }

any idea??

Where are you resetting lastDebounceTime? What value do you have for debounceDelay? What types are these variables?

If the code is just to illustrate debouncing, and your understanding, or lack thereof, of it, the code should not be so long that you can't post all of it (using the # button in the top row).

solved!

this is the modified part:

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: buttonState = reading;

if(wasPressing) { if(buttonState == LOW) { if(toggle == HIGH) toggle = LOW; else toggle = HIGH; } } wasPressing = buttonState == HIGH; }

@PaulS: the code is the same from this example: http://arduino.cc/en/Tutorial/Debounce

so, my entire code now is the following:

/* Debounce

Each time the input pin goes from LOW to HIGH (e.g. because of a push-button press), the output pin is toggled from LOW to HIGH or HIGH to LOW. There's a minimum delay between toggles to debounce the circuit (i.e. to ignore noise).

The circuit: * LED attached from pin 13 to ground * pushbutton attached from pin 2 to +5V * 10K resistor attached from pin 2 to ground

  • Note: On most Arduino boards, there is already an LED on the board connected to pin 13, so you don't need any extra components for this example.

created 21 November 2006 by David A. Mellis modified 3 Jul 2009 by Limor Fried

This example code is in the public domain.

http://www.arduino.cc/en/Tutorial/Debounce */

// constants won't change. They're used here to // set pin numbers: const int buttonPin = 2; // the number of the pushbutton pin const int ledPin = 7; // 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 boolean wasPressing = false; int toggle = LOW;

// 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); }

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: buttonState = reading;

if(wasPressing) { if(buttonState == LOW) { if(toggle == HIGH) toggle = LOW; else toggle = HIGH; } } wasPressing = buttonState == HIGH; }

// set the LED using the state of the button: digitalWrite(ledPin, toggle);

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