Joerg and I discussed today how to verify that the MICBIAS buzz rework was done properly. Joerg had a very interesting idea: by toggling the codec's MICBIAS output, we should be able to create noise that would vary depending on whether the rework has been done. He asked me to adapt one of my I2C-tweaking programs for this purpose.
Here's a little program that hammers the Wolfson as fast as it can, making MICBIAS oscillate at about 50Hz: http://svn.openmoko.org/developers/werner/wolfhammer/ The result looks like this, on a non-reworked A6, measured on the codec side of R4305: http://people.openmoko.org/werner/a6-nrw.png The amplitude seems pretty small (and I have plenty of ambiental noise), so I'm not sure if this is good enough. To verify that MICBIAS was indeed being toggled, I added a 1k resistor between the measurement point to ground (i.e., parallel to R4305 and C4302), which yielded this: http://people.openmoko.org/werner/a6-nrw-1k.png Joerg, I hope this is useful. - Werner _______________________________________________ hardware mailing list [email protected] http://lists.openmoko.org/mailman/listinfo/hardware
