You are of course correct. This is my error.

Better code:

if B and not SaveB then

    if A is high then increment the controlled value
    else decrement the controlled value

endif

Set SaveB to B

It is really that simple (now that I got it right).

Bob Ammerman
RAm Systems


----- Original Message -----
From: "Hazelwood Lyle" <LHazelwood@MFGNC.COM>
To: <PICLIST@MITVMA.MIT.EDU>
Sent: Wednesday, June 26, 2002 4:05 PM
Subject: Re: [EE]: "digital" knobs/buttons


Bob,
I respectfully disagree, or perhaps
I'm just woefully confused.

If you look for ANY change in B,
either rising or falling, then the
pseudo-code you provided will
"wiggle" back and forth between
increment and decrement, as the
input is turned in a constant direction.

Unless you differentiate between
"B Rising" and "B Falling", the state
of A will move you back and forth.

Now, if Either B rising OR B Falling
inverts A before the test, you'll
have one method of doing the two
step per cycle option that I failed
to cover in my previous letter.


I could be all wrong.. I am open to
hear more. Please elucidate.

I sketched up a chart to follow the
changes, I'll head home and pic up
the thread from there.

P.S.
I didn't start this thread, but I'll
be ordering a few encoders this week to
upgrade a project from pots, so I am
quite interested to see where it goes.

Lyle Hazelwood



-----Original Message-----
From: Bob Ammerman [mailto:rammerman@ADELPHIA.NET]
Sent: Wednesday, June 26, 2002 3:45 PM
To: PICLIST@MITVMA.MIT.EDU
Subject: Re: [EE]: "digital" knobs/buttons


I would just poll the inputs in a fixed-time based interrupt routine.
For
normal manual rotation you'd have no trouble keeping up.

Assume the two inputs are called A and B.

We have a value called and 'SaveB'

On each interrupt:

if B <> SaveB then

    if A is high then increment the controlled value
    else decrement the controlled value

    Set B to SaveB

endif

It is really that simple.

Bob Ammerman
RAm Systems

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