Bob Japundza wrote:
> Hi All,
>
> I was wondering if my code below can be made to be a bit better.  It works fine as is, but just seems to be a bit clunky to me.  In a nutshell what I'm doing here is checking two buttons on port A, turning off/on the motor and if one button is pressed, that dictates motor direction.  I'm wondering if there's a way without using the temporary register "button_status" to check the the two bits I'm looking at.
>
> movlw b'00001100'
> andwf PORTA,W                           ;mask all but the RA2,3 bits
> movwf button_status
> movlw b'00001100'
> xorwf button_status,w
> btfsc STATUS,Z                          ;are both buttons pressed?
> goto stopmotor                          ;yes, stop the motor
> movlw b'00001100'
> andwf button_status,w
> btfsc STATUS,Z                          ;are both buttons not pressed?
> goto stopmotor                          ;yes, stop the motor
> btfsc PORTA,2                           ;check if up button is on
> goto motorup
> btfsc PORTA,3                           ;check if down button is on
> goto motordown

While it would seem that testing that a key is pressed would seem
simple, it actually isn't because most applications need to know
when it was RELEASED as well. In fact, for me, a keypress occurs when it
is PRESSED THEN RELEASED.

About 10 years ago I began using a bulletproof way to process keys:

1. I read the keys- all of them- every 10ms or so. I can either read 'em
all at one tome, or rotate so that I read each one on a rotating basis.
Doesn't matter how its done, it works perfectly regardless.

2. Every 10ms I read the key and shift its value into a register
decicated just for that application.

3. If the key is ZERO when it is pressed, I look for the pattern
b'11110000' on that key's register. When that is seen, that key was
PRESSED AND RELEASED, so set a flag. To prevent more action, jam the
key's register with '11111111' so it can't be used again.

This works great. If anyone is interested, I'll publish some code.

-- Just Another Bob
--

Replier: Most attachments rejected
       --------------
         Bob Axtell
PIC Hardware & Firmware Dev
   http://beam.to/baxtell
       1-520-219-2363

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