It's not clear for me what you'd meant when said "...don't want use interrupt". Don't you want use additional interrupt or using ones a whole?. As well I have not any idea what an environment you're prefering for programming (ASM, Basic, C)?

Nontheless, your function() shouldn't be called by a static EVENT (whether switch pushed or not) but dynamic (tranistient) one. i.e whether there had been transition from switch ON state to switch OFF state.

In a nutshell my supposition is (excuse me for some mixing style as I dont know your prog language)

initialState=PortA:Bit2;

....timeDelay;

postState=PortA:Bit2;

IF (initialState==0 and postState==1) {call your function()}

else passing by...

.....

TimeDelay is conventialy called procedure to organize some time gap between Port readings. It can be organized simply if you place initialState calling quite apart from postState at your program.

Event is function of initialState and postState i.e. EventFunc(initialState, postState). EventFunc has four possible state and I for example used to prefer programming respond of system on all these states, using for instance switch statement on C. Some tricks with pointers would be possible here as well. But it's up to you.

Hope it helps.

P.S. You can put capacitor(some pF) between your switch and ground :).

When you have received the function release the button

Could this be a problem due to switch bounce??

John.

I would tend to use a location in memory as a status register and select one bit of the register to correspond to the switch. The other bits are free to use for other functions.

Check the condition of the switch.

If switch is 0, set your status bit to 0

If switch is 1 (activated) check status bit

If status bit is 0, perform switch routine and set status bit to 1

If status bit is 1, the routine has executed so ignore it.

Thus the switch has to return to the inactive state before the routine will run again.

Bill