If you could record from the microphone by software on the Freerunner, that would be great. <br><br>I would like to see confirmation that speaking at a conversational level to the microphone will give a nice signal level that fully uses the 16 bit range, and also show to some extent the degree of noise at the microphone. I did some recording tests a few months ago, and was never able to get a good signal level.<br>
<br>Because of the degree of complexity of the audio path (both hardware & software), I think it would be nice if OpenMoko had such test software to verify that microphone recording works well, and that the level is ok as part of your test suite.<br>
<br>Regards,<br><br>Erland<br><br><div class="gmail_quote">2009/1/13 Werner Almesberger <span dir="ltr"><<a href="mailto:werner@openmoko.org">werner@openmoko.org</a>></span><br><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
Joerg and I discussed today how to verify that the MICBIAS buzz rework<br>
was done properly. Joerg had a very interesting idea: by toggling the<br>
codec's MICBIAS output, we should be able to create noise that would<br>
vary depending on whether the rework has been done. He asked me to<br>
adapt one of my I2C-tweaking programs for this purpose.<br>
<br>
Here's a little program that hammers the Wolfson as fast as it can,<br>
making MICBIAS oscillate at about 50Hz:<br>
<a href="http://svn.openmoko.org/developers/werner/wolfhammer/" target="_blank">http://svn.openmoko.org/developers/werner/wolfhammer/</a><br>
<br>
The result looks like this, on a non-reworked A6, measured on the<br>
codec side of R4305:<br>
<a href="http://people.openmoko.org/werner/a6-nrw.png" target="_blank">http://people.openmoko.org/werner/a6-nrw.png</a><br>
<br>
The amplitude seems pretty small (and I have plenty of ambiental<br>
noise), so I'm not sure if this is good enough. To verify that<br>
MICBIAS was indeed being toggled, I added a 1k resistor between the<br>
measurement point to ground (i.e., parallel to R4305 and C4302),<br>
which yielded this:<br>
<a href="http://people.openmoko.org/werner/a6-nrw-1k.png" target="_blank">http://people.openmoko.org/werner/a6-nrw-1k.png</a><br>
<br>
Joerg, I hope this is useful.<br>
<br>
- Werner<br>
<br>
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</blockquote></div><br>