XS1 audio - clocks generation problem

Discussions about USB Audio on XMOS devices
genap
Experienced Member
Posts: 99
Joined: Sat Aug 31, 2013 11:23 pm

XS1 audio - clocks generation problem

Post by genap »

I have XS1-U8A usb audio (TDM8, inputs only, 48kHz) project with the XMOS as a master.
Most of the time LR and BCLK are generated properly on power-up (pic 1).
1-48kHz_frame.jpg
But sometimes on power-up the LR frequency is about 45.2kHz instead of 48, with some jitter.
I've noticed that in this case the first bit in each 32-bit channel is longer (high level is 5 times longer than normal, occasionally jumping to 4 times, therefore is jitter).
It makes LR pulse longer and LR frequency lower. See pics 2 and 3.
2-45.2kHz_frame.jpg
3-45.2kHz_LR_BCLK.jpg
I had quite a few XS1 audio projects, but never saw anything like this.
Is there any explanation to this situation?
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Ross
XCore Expert
Posts: 973
Joined: Thu Dec 10, 2009 9:20 pm
Location: Bristol, UK

Post by Ross »

Did you resolve this?