[Trac #743] Touchpad generates spurious coordinates

[Zarro Boogs per Child]

#743: Touchpad generates spurious coordinates
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 Reporter:  wmb at firmworks.com  |       Owner:  mfoster  
     Type:  defect             |      Status:  new      
 Priority:  normal             |   Milestone:  Untriaged
Component:  hardware           |    Keywords:           
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 The attached diagnostic illustrates a touchpad problem.

 To run the diagnostic, copy the file to a USB key, boot to the ok prompt
 with the key installed, then:

   ok fload disk:\touchpad.fth
   ok test mouse

 The diagnostic displays the coordinates of GS and PT packets, auto-
 switching between GS and PT mode.   The coordinates are absolute - if the
 touchpad packet reports X=12, Y=30, the diagnostic will put a dot on the
 display at column 12, row 30.  (The diagnostic does not display packets
 where the pen/finger down indicator is clear).

 To observe the problem, using your finger, lightly tap on the glide area
 near the right side.  In some cases, you will see a cluster of dots on the
 screen corresponding to the location where you tapped.  In other cases,
 you will see a line of dots scattered from the left of the glide display
 area to the tap area.  That indicates that the pad is generating spurious
 coordinates in some of the packets.

 Another way to see a related problem is to touch your finger lightly to
 the pen area to the right of the glide area (so lightly that it doesn't
 register as a pen event), then move it smoothly over the glide area from
 right to left.  Instead of displaying a smooth path from right to left,
 the path will often start in the middle of the glide display and then
 eventually jump over to the right before starting to track properly.

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Ticket URL: <http://dev.laptop.org/ticket/743>
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