Waitpeq to monitor a change in 2 pins? Possible????

TJHJ

Hi all,
So I am trying to pick up a simple optical encoder. I have a cased phototransistor set, and a disc that is cut with missing slots. Each high low transition on a pin is a given distance movement.
My issue is I don’t want to give up 2 cogs to watch the encoders, I don’t mind giving up one…
To monitor just 1 encoder I dedicate off a cog and have it doing the following, I am doing it like this so I don’t miss a transition.
·

Repeat 
  waitpeq(|<XEncoder, |<XEncoder,0) &#8216;wait for pin high 
  waitpne(|<XEncoder, |<XEncoder,0) &#8216; wait for low 
  XPosition ++&#8217;add to position 

·
But can I do something to watch for a change in either pin?

Repeat 
  waitpeq((|< XEncoder & |<Yencoder), ((|< XEncoder & |<Yencoder),0)  &#8216;does it compare the whole mask or just the pins set in state component? 
  waitpne(|< XEncoder & |<Yencoder), ((|< XEncoder & |<Yencoder),0)  &#8216;does it compare the whole mask or just the pins set in state component?   HorCurrentPosition ++
if ina[noparse][[/noparse]xEnxoder] == 0 
                XPosition ++ 
Elseif ina[noparse][[/noparse]yEncoder] == 0 
                YPosition ++
 

·
I think this will cause it to wait for a matched transition set. Not one or the other.....
I am thinking there is a way to do this alot simpler, but I am getting hung up on my bit math……
Any ideas or help is appreciated.
·
TJ

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I owe everyone here a bunch, So thanks again for answering my dumb questions.
Projects. RG500 ECU system. PropCopter. Prop CanSat. Prop Paste Gun.
Suzuki RG500 in a RGV 250 frame.
Bimota V-Due (Running on the fuel injection system)
Aprilia RS250

Phil Pilgrim (PhiPi)

Something like this ought to work:

[b]CON[/b]

  enca          = 0             'Pin number for encoder A.
  encb          = 1             'Pin number for encoder B.

  encamask      = 1 << enca
  encbmask      = 1 << encb
  mask          = encamask | encbmask

[b]PUB[/b] encoder | prevstate, change

  prevstate := [b]ina[/b] & mask
  [b]repeat[/b]
    [b]waitpne[/b](prevstate, mask, 0)
    change := ([b]ina[/b] & mask) ^ prevstate
    [b]if[/b] (change & prevstate & encamask)
      'Do encoder A stuff on falling edge.
    [b]if[/b] (change & prevstate & encbmask)
      'Do encoder B stuff on falling edge.
    prevstate ^= change    

-Phil

Post Edited (Phil Pilgrim (PhiPi)) : 10/13/2009 7:05:19 PM GMT

TJHJ

Wait will this wait for the whole transition? Don't I need 2 wait pin's to prevent it from looping around again if the pin didn't change states, while it was doing the update?

Thanks a bunch Phil, I was thinking way to hard here..
TJ

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
I owe everyone here a bunch, So thanks again for answering my dumb questions.
Projects. RG500 ECU system. PropCopter. Prop CanSat. Prop Paste Gun.
Suzuki RG500 in a RGV 250 frame.
Bimota V-Due (Running on the fuel injection system)
Aprilia RS250

Post Edited (TJHJ) : 10/14/2009 6:31:34 PM GMT

Phil Pilgrim (PhiPi)

The waitpne waits for any change from the previous state (low->high, high->low, on either or both pins). If if statement conditions are true only if the transition is high->low for the selected pin. If neither condition is true, it just goes back to the waitpne without doing anything and waits for the next change.

NOTE: It's vitally important that ina be read only once in the loop. If your encoder logic needs the value of ina for anything, it will take two lines of code to compute a value for change, viz:

    ...
    [b]waitpne[/b](prevstate, mask, 0)
    inaval := [b]ina[/b] & mask
    change := inaval ^ prevstate
    ...

Then use inaval in your code instead of ina. This will prevent weirdness should ina change between reads.

-Phil