#12161 HIGH 13.1.0: Touchscreen on XO-4 B1 aliases the touchpoints

Zarro Boogs per Child bugtracker at laptop.org
Sat Oct 27 03:20:19 EDT 2012

#12161: Touchscreen on XO-4 B1 aliases the touchpoints
           Reporter:  pgf          |       Owner:                                   
               Type:  defect       |      Status:  new                              
           Priority:  high         |   Milestone:  13.1.0                           
          Component:  touchscreen  |     Version:  Development build as of this date
         Resolution:               |    Keywords:  xo-4, touchscreen                
        Next_action:  diagnose     |    Verified:  0                                
Deployment_affected:               |   Blockedby:                                   
           Blocking:               |  
Changes (by tonyforster):

 * cc: tonyforster (added)


 This looks like its inherent to the design rather than a bug to me. The
 sensor looks like its optical. With 2 fingers it gets obstructions on two
 rows Ya Yb and 2 columns Xc and Xd. It has no way of knowing which 2 pairs
 of X Y to associate if you move the points round.

 The problem is when the points are vertically aligned or horizontally
 aligned, then rotation in one direction gives the same data as counter
 rotation for aliased or swapped points.

 Another way to trick the system: run your fingernail along 2 screen edges,
 a cursor appears at the intersection of X and Y

Ticket URL: <http://dev.laptop.org/ticket/12161#comment:1>
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