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A simple "skeleton" control structure

Suitable for many projects

In this tutorial, I am going to show you a simple control structure you might want to employ for some projects.

I used it again in January 2015, when playing with some WS2812 smart LEDs... lots of fun... but you could use it in lots of circumstances.

Confession: I haven't tried the following code! If there are little errors, consider them "exercises for the student". I hope the overall "genius" of the control structure I am going to describe will be clear.

Imagine that you had an Arduino with three momentary switches on three inputs. Button down, input reads High, not down, low. So, if you take the three buttons together, you can have 0 (up/up/up) to 7 (on/on/on) "on" the inputs... and the 6 numbers in between, also, of course.

It would be easy to write a function which would return the number "showing" on the inputs. We'll assume one called "bIPsSay", for "inputs say".

Further imagine that you have a fancy three color LED attached to an output pin, and that you only have to "say" MakeLED(255,128,0) to make that LED shine with full red (255), half green (128) and no blue. Change the numbers, change the color and brightness.

NOW assume you want to "show off" this wonderful device. So you write the following.... (which would need a setup() subroutine, would need "bIPsSay()" set up, etc... we'll assume those things done.)

void loop
{
if (bIPsSay()==0)
  {
  MakeLED(0,255,0);//green
  delay(300);
  MakeLED(0,0,0);
  delay(80);
  }
if (bIPsSay()==1)
  {
  MakeLED(255,0,0);//red
  delay(100);
  MakeLED(0,0,0);
  delay(80);
  MakeLED(255,0,0);//red
  delay(100);
  MakeLED(0,0,0);
  delay(80);
  MakeLED(255,0,0);//red
  delay(100);
  MakeLED(0,0,0);
  delay(80);
  }
};//end of "loop()

That's pretty crudely done, but will serve our purposes. You should be able to see that if no buttons are pressed, the tri-color LED winks gently in green, but if the first button is pressed, the tri-color LED winks red, rapidly.

But. There's already a problem. If you press the first button briefly, you will still get three "rounds" of "red on"/ "red off"... even though you stopped asking for that a little time ago.

In this particular program, that probably would be no big deal. But: Suppose that what the computer does when you press the first button goes on for, say, ten seconds. Surely, it should stop doing the "button 1 pressed" behaviour just about as soon as the button is released? And the current program doesn't do that.

The current program is giving an example of "blocking". Once the "button 1" "show" has started, the input buttons are "blocked"... the program doesn't "see" the change of the button state. But we can fix that!...

Consider the following....

void loop
{
if (bIPsSay()==0)
  {
  MakeLED(0,255,0);//green
  delay(300);
  MakeLED(0,0,0);
  delay(80);
  }
if (bIPsSay()==1)
  {
  MakeLED(255,0,0);//red
  delay(100);
    if (bIPsSay()==1)
      {
       MakeLED(0,0,0);
       delay(80);
       }
    if (bIPsSay()==1)
      {
       MakeLED(255,0,0);//red
       delay(100);
       }
    if (bIPsSay()==1)
      {
       MakeLED(0,0,0);
       delay(80);
       }
    if (bIPsSay()==1)
      {
       MakeLED(255,0,0);//red
       delay(100);
       }
    if (bIPsSay()==1)
      {
       MakeLED(0,0,0);
       delay(80);
       }
  }//end of first "if (bIPsSay()==1)..."
};//end of "loop()

That's crude, and you wouldn't need so many secondary "if (bIPsSay()==1)..."s... but I hope the way you can achieve a "menu" structure, and have it without blocking is clear to you now.

There would, of course, be other blocks...

if (bIPsSay()==2)
  {...
  }
if (bIPsSay()==3)
  {...
  }

... et cetera.

Concluding remarks

I hope that was clear? Useful? Let me know of anything you found poorly explained, and I will try to get this edited before the next reader suffers. Facebook "Like"s much appreciated. No point in writing these pages, if no one can find them.

If you use subroutines, as you should for all but the very, very simplest work, you can make the above look a lot better... but the basic idea will remain.




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