#9604 NORM 1.5-F11: build DC sensor mode on audio driver

Zarro Boogs per Child bugtracker at laptop.org
Sun Nov 15 22:01:59 EST 2009

#9604: build DC sensor mode on audio driver
           Reporter:  Quozl          |       Owner:  dsd          
               Type:  defect         |      Status:  new          
           Priority:  normal         |   Milestone:  1.5-F11      
          Component:  kernel         |     Version:  not specified
         Resolution:                 |    Keywords:               
        Next_action:  test in build  |    Verified:  0            
Deployment_affected:                 |   Blockedby:               
           Blocking:                 |  
Changes (by Quozl):

 * cc: wad (added)


 On os40 with a XO-1.5.

 Tried to test Measure activity, it displayed no waveform and was

 Checked ''alsamixer'', two new ''Playback'' controls are visible in this
 build; ''DC Input Bias'' (Off, 50%, 80%), and ''DC Mode Enable''.
 (Perhaps these should be ''Capture'' controls).

 Checked ''amixer'', the two new controls are properly present.

 Checked sample data using a command:
 arecord --file-type=raw --format=s8 | od -h
 and verified:
  * sample values were low with background office noise,
  * sample values were high with noise near laptop microphone,

 Then I enabled ''DC Mode Enable''.

 When connecting a 1.2V constant DC source with about 10k series
 resistance, the voltage at the laptop microphone input was zero, and the
 sample values output did not vary with a varying input voltage.

 wad: what do you think?

Ticket URL: <http://dev.laptop.org/ticket/9604#comment:6>
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