Latched buttons

[peu]

Hi, im building an application with a lot of loops and subroutines and I need to know every now and then if a button has been pressed.

I know that this can be accomplished by reading the port as often is possible, but I tought that by latching the port, when I have time to look at it and view if it changed from the last time it would be easier for my program structure.

to be clear, here is the metacode:

buton state=0
loop:
program runs
button is pressed (new state=1), buttons keeps this state
program continues
button is sensed and checked if it changed
loop

I know that at any given time the button may be pressed twice and I could miss that. This is something I can live with.

is there a simple way of accomplishing this?

thanks

[mister_e]

i still prefer to use interrupts. Once a button is pressed, it jump automatically to a X routine.

if you want to monitor few button, you can use Interrupt on PORTx change.

What else the program will do?

[Ioannis]

may be in your tight loop you could read all 8 bits of a port, store in a temp_port byte and process it later. The delay is minimum.

Of course that way you will miss the fast double clicks, but as you said you can tolerate this.

Best is interrupts as Steve stated.

Ioannis

[J. Mark Wolf]

I have such a circuit, and can email you a PDF later today. This circuit also handles debouncing, which the other suggestions don't allow time for.

[peu]

good ideas posted here, never tough of implementing that way, maybe because I never used the On Interrupt instruction before...

Will try, will tell

J. Mark: can you attach the PDF to a message, so all ppl see it?

Thanks

[Archilochus]

If you don't need instant response to the button press, you can get away with not using interrupts.
Just test the appropriate interrupt flag bit when you want to know if the button was pressed.
Remeber to clear the bit after checking it.