fade effect - 2 push buttons

Projects Programming
6

You never want to leave an input pin "open" because you will just read random noise. You should always use a resistor to connect the input pin to +5 (pull-up) or Ground (pull-down). That means there are two ways to connect a button:

If you use a pull-up resistor the button goes between the pin and Ground. Closing the button causes the input to switch from HIGH to LOW.

If you use a pull-down resistor the button goes between the pin and +5. Closing the button causes the input to switch from LOW to HIGH.

I tend to use the pull-up version because the Arduino has internal pull-up resistors that can be enabled in software:

// Old style, pre Arduino 1.0:
pinMode(inputPin, INPUT);
digitalWrite(inputPin, HIGH);

// New style, Arduino 1.0+:
pinMode(inputPin, INPUT_PULLUP);

Because of the internal pull-up resistors this form doesn't require an external resistor like the pull-down form does.