[alsa-devel] USB asynchronous mode feedback format

Julian Scheel julian at jusst.de
Thu Oct 14 17:10:01 CEST 2010

Am Donnerstag, 14. Oktober 2010, 13:16:12 schrieb Daniel Mack:
> > Sure, attached you see a capture while running speaker-test to generate a
> > 1khz sine wave on one channel. (Blue: BCLK 1,536MHz, Yellow: LRCLK:
> > 48kHz, Green: I2S data)
> > If you want to see more/other captures just let me know what you need.
> The dump doesn't show whether the LRCLK is symmetrical, iow, whether the
> low phase of LRCLK has the same number of BCLK cycles as the high phase.
> But if that's the case, the signals do indeed look alright. Maybe you
> need the configure the codec to this format?


I did a capture of the same signal, but this time not just a short snap, but a 
whole memory dump of the oscilloscope. I did a plot with gnuplot and uploaded 
it here:

As it's 0,5MB big I didn't want to send it as attachment...

Would you agree that the data (this time blue channel) is delayed too much? 
Looks like it's at least 2 cycles behind the LRCK toggle.
Would it be possible that this is the reason for the DAC not understanding the 


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