Keypad Code

[gregmcc]

I've been looking through the keypad code from Nigel's tut site () and would like to include it in my program.

My asm is a bit rusty but from going through the code 'KEYS' procedure goes into a loop intul a key is pressed.

In the program I am writing I need to constantly check one of the RA ports for a input so the program cannot loop at the keys subroutine otherwise it will never get to the input checking routine. What I need is something like:

Main
call check_keys
; above routine should return the key pressed in W, otherwise W=0
; if W<>0 Then do something here

call check_ra2

loop Main

How do I go about getting the keypad routine to not loop until a key is pressed?

 

[Nigel Goodwin]

I've been looking through the keypad code from Nigel's tut site () and would like to include it in my program.

My asm is a bit rusty but from going through the code 'KEYS' procedure goes into a loop intul a key is pressed.

In the program I am writing I need to constantly check one of the RA ports for a input so the program cannot loop at the keys subroutine otherwise it will never get to the input checking routine. What I need is something like:

Main
call check_keys
; above routine should return the key pressed in W, otherwise W=0
; if W<>0 Then do something here

call check_ra2

loop Main

How do I go about getting the keypad routine to not loop until a key is pressed?

Simply alter the routine so it only loops a number of times then gives up, return an unused value (like 255) in W so you can check if a button was pressed or not (or set a flag).

 

[gregmcc]

Thanks - now why didn't I think of that

 

[bibinjohn]

See key debouncing problems. If you want to avoid it use 74922

Code for interfacing Keypad with parallel port of a computer is available in book
MY EXPERIENCE IN PARALLEL PORT INTERFACING
It is a free book. You can get it from yahoo group-booksbybibin

https://groups.yahoo.com/group/booksbybibin/

Bibin John
www.bibinjohn.tk

 

[akg]

or a 40-50ms delay and re-checking the keystate will be sufficent for debounce

 

[Nigel Goodwin]

or a 40-50ms delay and re-checking the keystate will be sufficent for debounce

Yes, software de-bouncing makes a LOT more sense than adding a 74992.