Help reading simple four quadrant encoder disk with BS2

WHall

I could use some help. I've created a simple four quadrant encoder disk (attached) that I can use with the QTI IR sensor to debug 1's and 0's. Circuitry is good, and manually moving the disk past the sensor works perfectly. But I'd like to take the bit read from the encoder to pulse a servo one quarter turn (which is why the encoder disk is so simple), then stop and wait for the next command to make a quarter turn, and so on.

My thought is to monitor the bit and tell the servo to stop turning when the bit changes from a "1" to a "0" (or vice versa). Conceptually, it seems simple (isn't that always the case!), but my lack of coding experience is killing me. I could use some help with the section below. What am I doing wrong? Do I need a write/read command? Any help for a newbie would be most appreciated!

Motor PIN 12

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[noparse][[/noparse] Constants ]

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Motorstop CON 750

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[noparse][[/noparse] Variables ]

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qti VAR BIT
old VAR BIT

DO
HIGH 5
PAUSE 1
qti = IN3
INPUT 5
qti = old
PULSOUT motor, 850
IF (qti <> old) THEN
PULSOUT motor, motorstop
ENDIF
LOOP

sam_sam_sam

Look at this post to get·some ··s on how to do this

http://forums.parallax.com/showthread.php?p=893416

I hope this helps

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·Now wanting to learn Spin· Thanks for any··that you may have and all of your time finding them

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Sam

Zoot

Your logic is bad. Plus you'll need a state to keep track of what you want the servo to "wait" for (a change in encoder edge, or a command to start again).

state = 0  ' 0 = moving and waiting for encoder edge; 1 = waiting for "command" to start again

DO 

  old = qti ' save the last reading BEFORE doing new reading    
  HIGH 5    ' charge cap
  PAUSE 1  ' wait
  qti = IN3 ' read it
  INPUT 5 ' make an input

  IF state = 0 THEN  ' moving waiting for edge
      PULSOUT motor, 850 
      IF (qti <> old) THEN     ' must be new edge
         state = 1
      ENDIF
  ENDIF

  IF state = 1 THEN  ' stopped, waiting for "command" -- not sure where command is coming from? so let's say a simple button press
     PULSOUT motor, motorstop 
     IF buttonIn = 1 THEN
       state = 0
     ENDIF
  ENDIF

LOOP

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When the going gets weird, the weird turn pro. -- HST

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Post Edited (Zoot) : 4/20/2010 10:05:02 PM GMT

WHall

Zoot, "Your logic is bad." If you only knew Many thanks for helping with the code! I've been really struggling with it - I'll your example and report back on how it worked.