' {$stamp bs2}

' Program to act as high speed quadrature counter


' Program Name: quadhicount.bs2
' Last Update: Mar 10/01 tjs

DIRH=%11111111

counter VAR Word
counter2 VAR Word
counter3 VAR Word
old VAR Nib
new VAR Nib
direct VAR Byte

' Channel a and b of encoder go on inputs 6 and 7 in this case.
quad:
   counter=127         'load a dummy value so can count up or down
   new = INB & %0011      ' get initial condition

start:
   old = new & %0011      ' remember initial setting

again:
   new = INB & %0011      ' get new reading
   IF new=old THEN again
   direct=new.BIT1 ^ old.BIT0   ' XOR left bit of new with right bit of old to get direction
   IF direct=1 THEN cw      ' jump here to increment
   LOW 0                    ' pin 0 turns led off id turning counter-clockwise
   counter=counter-1         ' jump here to decrement
   OUTH=counter.LOWBYTE
   GOTO start

cw:
   HIGH 0   ' pin 0 turns on led if turning clockwise
   counter=counter+1
   OUTH=counter.LOWBYTE  'turn on leds on pins 8 through 15 to watch count
   GOTO start