Mic input

[Bert Freudenberg]

Am 11.10.2006 um 15:51 schrieb Jim Gettys:

> On Wed, 2006-10-11 at 15:13 +0200, Bert Freudenberg wrote:
>> Hi,
>>
>> I connected a headset (analog mic and phones) to an A-test board.
>> Sound output works fine after "alsaunmute". I have difficulties with
>> input, though.
>>
>> I unmuted "Mic" in alsamixer, and tried arecord. Nothing is recorded.
>> "V_REFOUT" does make a difference, it connects in and out so I hear
>> what I'm saying directly (even more so if I enable "Mic boost").
>> However, in arecord I still get silence.
>>
>> So - what do I need to do for mic recording? Does this have to do
>> with the analog input, do I have to switch that off?
>
> Of course you have to switch it off; otherwise we'd have it on all the
> time and have no control at all.

That's why I assumed it would be off by default.

The only documentation I could find is in a mailing list thread  
(http://mailman.laptop.org/pipermail/devel/2006-July/000672.html):

	*a- tell the EC to turn on MIC_AC (ie: bypass C35 and R25) [ OLPC  
specific ]
	*b- tell ALSA to disable VREFOUT and the high pass filter [ AD1888  
specific ]

So how do I "tell the EC to turn off MIC_AC"?

> Whether this is actually your problem, only you can tell.

Well, is it normal that enabling this loops the mic directly to the  
phones?

- Bert -