#11485 NORM 1.75-so: XO-1.75 OS12 reports constant brightness to TurtleArt

[Zarro Boogs per Child]

#11485: XO-1.75 OS12 reports constant brightness to TurtleArt
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           Reporter:  tonyforster   |       Owner:               
               Type:  defect        |      Status:  new          
           Priority:  normal        |   Milestone:  1.75-software
          Component:  not assigned  |     Version:  not specified
         Resolution:                |    Keywords:               
        Next_action:  never set     |    Verified:  0            
Deployment_affected:                |   Blockedby:               
           Blocking:                |  
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Comment(by pgf):

 this is by design.  it's advantageous to limit the amount of time spent
 reading the light sensor, because time spent reading it is time during
 which the storage LED can't blink (since it interferes with the reading).
 to make all cases work, the longest reading the sensor driver will take is
 MAX(high_lim, ceiling) where high_lim is the high hysteresis limit,
 currently set by powerd to 80, and ceiling is initialized by default to 0.

 if you want longer readings, e.g., if turtle art wants to get the full
 range possible, TA needs to write a value to the /sys/devices/platform
 /olpc-ols.0/ceiling.  the absolute maximum value that can be written is
 10000.  dark room readings are something like 5000.

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Ticket URL: <http://dev.laptop.org/ticket/11485#comment:1>
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