#9851 LOW 1.5-sof: XO-1.5 audio input has a DC offset at high gain

[Zarro Boogs per Child]

#9851: XO-1.5 audio input has a DC offset at high gain
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 Reporter:  Quozl     |                 Owner:  wad                              
     Type:  defect    |                Status:  new                              
 Priority:  low       |             Milestone:  1.5-software-update              
Component:  hardware  |               Version:  Development build as of this date
 Keywords:  os54      |           Next_action:  diagnose                         
 Verified:  0         |   Deployment_affected:                                   
Blockedby:            |              Blocking:                                   
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 Reading the digital samples from the sound device shows a positive DC
 offset of up to 0x1000 out of 0x10000, when the mixer ''Capture'' level is
 set to maximum, and the ''Analog Mic Boost'' is set to 40dB.  Lowering
 these levels or the ''Digital'' level reduces the offset.  Changing ''DC
 Input Bias'' has no effect (''DC Mode Enable'' is off).

 Test data generated using this command:
 {{{
 arecord --format u16 --file-type raw - | od -h
 }}}

 The offset is also visible in Measure activity, but the above test
 excludes the activity as the source of the offset.

 XO-1.5 os54, internal and external microphone.

 No offset was seen on XO-1 build 802.

-- 
Ticket URL: <http://dev.laptop.org/ticket/9851>
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