Increment when a button is pressed?

Vaati

I need to increment a variable once for each change of a boolean variable from false to true. Is this possible?

The alternative way I can write it is that I need to increment a value every time a button is pressed, but the following code increments it until the button is released:

if(ui.btnup)
  my_var++
if(ui.btndn)
  my_var--

FYI, I'm using the jm_lcd_ui object, since I have the GG Prop Platform + LCD module.
Thanks.

Mike Green

When you talk about a change in a Boolean value, you're really talking about two Boolean values, one is the current value of the Boolean and the other is the previous value of the Boolean:

if newValue and not oldValue
   counter++    ' The oldValue was false and the newValue is true
oldValue := newValue   ' Update oldValue

doggiedoc

Vaati,

When your code checks the state of the boolean variable, use intermediate variables to compare the last state of your boolean variable and increment your counter variable accordingly.

Or maybe: using the CASE instead. I'll try an example and post.

Paul

doggiedoc

Dang, Mike Green you are fast.

doggiedoc

Vaati - do you need to count each transition of the Boolean value or just when it goes from False to True?

Vaati

Mike Green,

Correct me if I'm wrong, but that would continue to increment until newValue becomes false, correct? I need to increment only once per change from false to true.

Basically, when the up button is pressed on the module I'm using, ui.btnup becomes true. I need to increment a value each time that up button is pressed, yet my code in my first post increments it until the button is released.

MagIO2

  if oldval <> newval
    oldval:=newval
    if newval
      count++

Of course this code is only good if newval is already debounced. If not there might appear more counts due to the bouncing. Easy way of adding debounce is to wait for some ms (say 20) inside of the if oldval<>newval.

Mike Green

@Vaati, Nope. The counter will be increment only when the "new" value is true and the "old" value is false. The next time through, the "old" value will be true and the counter will not increment. This is standard software positive edge detection. The counter will increment once only for each button push or click. The button has to be released, then pushed again for the count to increment.

Vaati

Ok, I see what you mean -- however, it isn't working in this case.

I probably should reword my question -- how do I increment something each time a button is pressed, and only once per press?

Mike Green

Either what I posted or what MagIO2 posted will do what you want. Initialize oldBtnup and oldBtndn to false, then

newBtnup := ui.btnup
if newBtnup and not oldBtnup
  my_var++
oldBtnup := newBtnup
newBtndn := ui.btndn
if newBtndn and not newBtndn
  my_var--
oldBtndn := newBtndn

Vaati

Oh, ok -- thanks!

I suggest an edit, for someone who might find this thread later -- your code should be

if newBtndn and not oldBtndn

instead of how it is now. ;-)

tonyp12

Gone need software debounce, unless you already using hardware debouce.
http://www.maxim-ic.com/app-notes/index.mvp/id/287