Below is a simple circuit that uses an ordinary push button to light up an LED. Normally I’ll need a pull-up resistor as shown in the red box, but with the built-in pull up resistors, I can totally remove that part and save myself a resistor and some hassle when routing PCBs.
As an example, I’ll be using the sample sketch found in the Arduino IDE. It’s located under Examples -> 02. Digital -> Button.
The only difference was I added a line that enables the built-in pull up resistors.
See the video below to see it in action :
The only downside is, it doesn’t have built-in pull down resistors.
This shouldn’t be too much of a problem because the normal practice in electronics will be to use pull-ups and detect LOW signals.