[Bugs] #2527 UNSP: Turtleart sensors buggy on XO1.5

[Sugar Labs Bugs]

#2527: Turtleart sensors buggy on XO1.5
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    Reporter:  tonyforster                |          Owner:  walter                     
        Type:  defect                     |         Status:  new                        
    Priority:  Unspecified by Maintainer  |      Milestone:  Unspecified by Release Team
   Component:  Turtleart                  |        Version:  Unspecified                
    Severity:  Unspecified                |       Keywords:                             
Distribution:  Unspecified                |   Status_field:  Unconfirmed                
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Comment(by tonyforster):

 Testing whether the calibration is now more reliable:
 All units XO-1.5 OS880 Sugar 0.94, measuring 22k+680 resistor on L
 channel, R channel o/c
 red/purple and green/purple are TA V114 SKU104
 Tony1.5 is TA V130 (as at yesterday) SKU99

 All units failed to initialise sometimes on first run after boot, they
 measured an erratic high value. They all then measured OK pressing stop
 then start (except once*)
 Failure rate to initialise after boot was:
 green purple 4/8
 red purple 3/8
 tony1.5 2/8

 Conclusion: TA V130 can only be at most marginally better

 * had a fail mode that I have not noticed before, (for these tests its 1
 in 48 trials). It measured OK after boot but after stop/start it measured
 a low 2k value, this fault did not clear for subsequent stop/starts. It is
 likely that the bias did not turn on.

 Also looked at calibration repeatability between units. Resistor marked as
 22k+680. Multimeter reads 23.7k, green/purple 24.4k, red/purple 21.4k,
 tony1.5 21.9k

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Ticket URL: <http://bugs.sugarlabs.org/ticket/2527#comment:4>
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