Sleep does not really sleep...

[Ioannis]

Hi Jerson.

Thanks for the good points. Yes I will change the ISR to what you suggested. But in any case as it is now, it works very good. With your suggestion will be more efficient and fast in regards of ISR view.

The PortB has Pull-Ups enabled so the line is correct as it is in the program.

My only problem is how to check for key release instead of key press.

Ioannis

[Jerson]

Not too difficult to check for key release to act on.

Right now you are checking a keypress when the portb value is different from $78

Key release is simply getting the transition from (Not $78) to $78

What caused it to be Not $78 is the key that got released.

For easy implementation in case of short keypresses, a tight blocking loop doing the above test is fine. In case you anticipate the user will have a button down for a long while, then a different approach using a software timer may give better results.

Just a short pseudo code as I am not well oiled in PBP these days

while 1
    key = ~portb & $78
    if (key <> $78) then
         savedkey = key
    else
         if savedkey <> $78 then
              ' saved key is the one that was released
              ' act on saved key
         endif
    endif
wend

If you wish to have a keyboard that has buttons that give pressed, hold, repeat and release states, I suggest you look at some arduino code that shows such an implementation using a finite state machine