#12325 NORM 4-softw: zForce: diagonal lines are not right

Zarro Boogs per Child bugtracker at laptop.org
Tue Jun 25 12:53:49 EDT 2013

#12325: zForce: diagonal lines are not right
           Reporter:  godiard        |       Owner:  Quozl            
               Type:  defect         |      Status:  closed           
           Priority:  normal         |   Milestone:  4-software       
          Component:  touchscreen    |     Version:  not specified    
         Resolution:  fixed          |    Keywords:  XO-4, touchscreen
        Next_action:  test in build  |    Verified:  0                
Deployment_affected:                 |   Blockedby:                   
           Blocking:                 |  
Changes (by wad):

  * keywords:  => XO-4, touchscreen
  * status:  assigned => closed
  * resolution:  => fixed


 This is a linearity problem, which we have spent a lot of time working on
 since this ticket was filed.

 The root cause turned out to be a skew of the IR PCB (receivers and
 transmitters) around the bezel, caused by a poor assembly technique.   We
 added larger alignment holes to both the IR light guide and the IR PCB,
 allowing the assembly process to use a jig with alignment pins to ensure
 minimal skew in volume production.

 We also added a linearity test to the manufacturing tests.   Every XO-4
 Touch laptop is tested for the linearity of a diagonal line drawn across
 the screen.    There is a test jig which helps the test operators do this
 quickly, but we started testing with a capacitive stylus and a straight

 The linearity is sensitive to the size of the finger being tracked.
 Testing at the factory is done with a 9mm wide stylus.

 Closing as solved, although attention to this will be required throughout

Ticket URL: <http://dev.laptop.org/ticket/12325#comment:6>
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