Best way to find a rising edge?

Hi,

My first post here! Seems like a great forum; glad to be a member. I need to know when an input pin sees a 0-5V transition (must do with several pins; don't want to use interrupts).

In C I'd do it this way:
byte old, nowHigh;
old = pin_in; // set old as the old value of the pin
pause 10
nowHigh = pin_in & !old; // set nowHigh if it is now high but used to be low

My newbie questions:
1) In PBP is it smarter to use BIT variables to do this?
2) How do I get the NOT operator (! in C) in PBP? Or do I have to do something like
nowHigh = (pin_in==1) AND (old==0) ?

And what kind of variable is nowHigh = (pin_in==1) AND (old==0) anyway? Is it a BIT since pin_in is a bit, or if nowHigh is a BYTE is it automatically typecast to a BYTE?

Thanks for shedding any light on this!

- Jim

----------

I did it like this

RESETALL VAR PORTA.0
RSTPLS VAR BIT
HULP0 VAR BIT


RSTPLS = RESETALL & ~ HULP0
HULP0 = RESETALL

(& = logical and ~ = invert)

' At RSTPLS you will get a pulse what is one cycle of your program if RESETALL goes high.

Ofcource
while
RESETALL = 1
wend

will also work

I am not sure exactly what you are trying to do ???

; If you are only looking for 0V-5V (and not 5V-0V) then try this
; example of monitoring RB0, RB2, and RB4 for change
old var byte
main:
pause 10
old = PORTB & %00010101
if old = 0 then main
; do something here because a pin went high
; to find which pin went high
if old.0 = 1 then here4RB0
if old.2 = 1 then here4RB2
if old.4 = 1 then here4RB4

here4RB0:
do something
goto main
here4RB2
do something
goto main
here4RB4
do something
goto main

Another approach - You also could just poll the port directly,
main:
If PORTB.0 = 1 then here4RB0
If PORTB.2 = 1 then here4RB2
If PORTB.4 = 1 then here4RB4
pause 10
goto main
etc

************************************************** ************
; If you are looking for 0V-5V or 5V-0V then try this
; example of monitoring RB0, RB2, and RB4 for change
old var byte
nowHigh var byte
main:
old = PORTB & %00010101
pause 10
newHigh = PORTB & %00010101
if old = newHigh then main ; no change on RB0, RB2, RB4
; do something here because a pin changed
old = old ^ newHigh ; find changed pin(s) (bit or bits will be set for changed pin(s))
if old.0 = 1 then here4RB0
if old.2 = 1 then here4RB2
if old.4 = 1 then here4RB4

here4RB0:
if newHigh.0 = 1 then
do something ; pin when from low to high
else
do something else ; pin went from high to low
endif
goto main
here4RB2
do something
goto main
here4RB4
do something
goto main

Good Luck,

Paul Borgmeier
Salt Lake City, Utah
USA

Wow, thanks Paul and Mat; that was fast! Exactly what I needed...I couldn't find the ~ negator in the manual, and I wasn't sure if logical true and false could be automatically typecast to a byte variable. From your code, now I know, and I have a bunch of things to try to see which minimizes the generated code.

Thanks,

- Jim