Accurate control of button repeat rate

Work in progress This article or section will be worked on in the upcoming hours or days. See history for the latest developments.

Background

Sometimes you might want to have control over the speed that a repeatable button works - maybe you want it to repeat exactly every 1.325 seconds, or you just want to slow it down. At the end of this article you will be shown how to use a button to set the frequency of a radio. This is certainly a time when the default (system) repeat rate of a button is too fast.

How it is done

The secret is in having a method of preventing a button from repeating until our chosen time has elapsed. It is possible, but messy, especially if you are doing this with a number of buttons, to do it inside the code for each button. It is much better to create a new type of button code. For this we need a class, and then create instances of this class for each controlled button. This, incidentally, is OOP, or Object Oriented Programming.

Here is thew code to create the new class. It is called timedControl. I have added (unnecessary) open lines between each member of the class to make understanding easier.

var timedControl = {
      last_busy: 0,

      timeout_dur: 1.0,

      new: func() {
          return { parents:[me] };
      },

      _call: func(fn, arg) {
        if (!arg) { me.last_busy = 0; return; }
        if (me.timeout_dur != nil) {
          if ((me.timeout_dur == -1) and me.last_busy != 0) return;
          var time = systime();
          if (time < me.timeout_dur + me.last_busy) return;
          me.last_busy = time;
        }
        return call(fn, [arg], me);
      }
};

Let's assume that we have a function, myFunction, which must only repeat every 0.25 seconds. We create it with

var myFunction = timedControl.new();

and set the repeat rate to 0.25 seconds with

myFunction.timeout_dur = 0.25;

How it works

var myFunction = timedControl.new() calls lines 6, 7, 8 of timedControl. This creates a new instance of timedControl named myFunction and returns a pointer to it. Now, whenever you use myControl it will point to where it exists in memory.

myFunction.timeout_dur = 0.25. myFunction points to the function in memory, .timout_dur then points to where timeout_dur exists in memory and changes its value to 0.25. Line 4 of the code set it to 1.0, just so it has a value.