[alsa-devel] USB asynchronous mode feedback format

Julian Scheel julian at jusst.de
Thu Oct 14 13:01:52 CEST 2010

Am Donnerstag, 14. Oktober 2010, 12:48:55 schrieb Daniel Mack:
> On Thu, Oct 14, 2010 at 12:27:38PM +0200, Julian Scheel wrote:
> > thanks a lot! You made my day (c:
> > Using EP5 for feedback makes it working. So I now get the data out even
> > in async mode. Currently I have a problem left that channel assignment
> > jumps here and then. Probably a buffering issue...
> > Also neither a SRC4192  (sample rate converter) nor a PCM1794 (dac) seem
> > to be able to understand what I am sending right now... Not sure why.
> > Looking at the measurements it really looks like a proper I2S signal.
> Can you send oscilloscope screenshots? Which data format are you using?

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.

Signal is 48kHz 16Bit. As it's I2S it is MSB with 1 BCLK-Cycle delay.

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