Why don't I have to set a digital pin to OUTPUT when using the tone function?

Projects Programming
1

Hi, just started using the Arduino, and I'm going through the Arduino Projects Book.

I was just wondering why I don't need to set the digital pin to OUTPUT when using the tone function when digital pins are INPUT by default.

I also tried setting the Digital Pin I used the tone function on explicitly to INPUT, and the project still worked, I mean the tone function still worked.

Same question applies to using Servo.attach..

When do I absolutely need to set it to OUTPUT and when does it automatically assume output?

Thank you to anyone for their time in answering this.

2

The Tone and Servo libraries do it for you. If they didn't people would complain that they used the library and it "doesn't work".

If you aren't using a library, then you would need to set the pin to output yourself, if that is what you want.

To be "absolutely" certain, for a particular library, you would need to look at the library code.

3

Thank you very much. That cleared things up. Is there a way to see what is from the library and what is primitive to the language?

4
  1. Learn the language.
    or
  2. Read the source code of the library, it is available.