mixer settings for voice recording?

Andy Green andy at openmoko.com
Tue Jul 29 15:49:51 CEST 2008


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Somebody in the thread at some point said:

| So, what is required to make the dsp-device delive audio-data?
|
| Q: The hardware does support this, right?

Yeah.

| Q: Is it a audio-driver problem, e.g. the alsa-device-driver for the chip
|    doesnt support audio capturing?
|
| Q: Is it a problem with my mixer settings? If so, which are the correct
|    mixer settings?

I can't give you a straight answer on what to do, but here is the
situation around it.

The normal audio routing for the microphone inside the WM8753 codec is
to bring it in on "MIC2" port and then send it via an "analogue path"
around some scalers and mixers and switches and send it back out again
on MONO1 / MONO2 to the GSM chip.  In short it doesn't get delivered to
the ADC in the Wolfson where you can pull it as normal PCM.

You can see it here:

http://wiki.openmoko.org/images/2/2c/WM8753_BlockDiagram_GSM_handset.png

If the PGA and mux are configured, it should work OK.

One last consideration, the Mic is OFF unless you enabled MICBIAS signal
to power it.

- -Andy
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