Subject:
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RE: Gutting an optical mouse - Part I
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Newsgroups:
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lugnet.robotics
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Date:
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Fri, 12 Jul 2002 20:53:05 GMT
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Original-From:
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Rob Limbaugh <RLimbaugh@&stopspammers&greenfieldgroup.com>
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Viewed:
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750 times
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> >
> > Clockwise
> > Detent? Bit 0 Bit 1
> > Y 0 0
> > N 0 0
> > Y 1 1
> > N 0 1
> > (pattern repeats 11 more times)
>
>
> It appears to me there is a slight mistake here. According
> to this, there is no way to distinguish between the first row
> and the second. I assume the second should be 10, so it
> would go 00 10 11 01.
I thought this was an error to, so I spent about an hour triplechecking my
findings. Bear in mind that the scroll wheel doesn't need 7.5-degree-per-step
accuracy, which is what that extra bit would give.
This is a chart of the data I collected when graphed.
Clockwise
___ ___ ___
Bit 0 | | | | | |
___.___| |___.___.___| |___.___.___| |___.
0 0 1 0 0 0 1 0 0 0 1 0
___.___ ___.___ ___.___
Bit 1 | | | | | |
___.___| |___.___| . |___.___| . |
0 0 1 1 0 0 1 1 0 0 1 1
Time ---.---.---.---.---.---.---.---.---.---.---.---
Counter Clockwise
___ ___ ___
Bit 0 | | | | | |
___.___| |___.___.___| |___.___.___| |___.
0 0 1 0 0 0 1 0 0 0 1 0
___.___ ___.___ ___.___
Bit 1 | | | | | |
___| |___.___| . |___.___| . |___
0 1 1 0 0 1 1 0 0 1 1 0
Time ---.---.---.---.---.---.---.---.---.---.---.---
As you can see, direction and velocity can be determined. Rapid oscillations in
a 7.5 or 15-degree arc could be problematic if only one of these was relied on.
On the other hand, it's possible I have a mouse with a bad part or ruined it...
too bad I voided the warranty! :)
Hope this clarifies things a bit!
Rob
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