Clock synchronization on xcore mic array

Voice related projects and technical discussions
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Joined: Sun Nov 05, 2017 4:09 am

Clock synchronization on xcore mic array

Postby PaulDSPC » Sun Nov 05, 2017 4:15 am

We are using the xcore microphone array with a linux development board ( 7). It appears as a USB audio device with 8 inputs and 2 outputs. We are measuring the round trip latency through the DAC -> Loudspeaker -> Microphones. We are seeing the round trip latency varying over time. When we repeat the test on the PC with the Thesycon drivers, then the latency is constant.

Are the microphones and DAC on the xcore board locked to the same clock? Is there anything that you can think of that would causing time varying latency in the system?
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Joined: Thu Aug 24, 2017 12:03 pm

Postby xmosbrendon » Tue Nov 07, 2017 2:34 pm

Sounds like the issue is coming from the linux development board. If you repeat the test with the PC and Thesycon driver do you continue to get constant latency?
If so then it points to the dev board being the most likely cause of the issue.

On the board side, we have a single clock source. It is sent to the DAC and MCLK of the chip. MIC CLK is a divided version of this and should remain synchronous.

It would be pure speculation but I would guess the host is taking a variable amount of time to process the USB on the dev board. Where the PC is more likely to have a constant time. Hopefully this helps!

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