6-mic array using GPIO clock

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colin.dente
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6-mic array using GPIO clock

Post by colin.dente » Wed May 29, 2019 7:17 pm

Hi,

The overview diagram for the 6-mic array shows a jumper which appears to allow the use of the GPIO clock instead of the on-board 24MHz oscillator.

I have an application which requires the DAC clocks on the microphone array to be phase locked with the RPi clock, so I would like to be able to use this feature. Does anyone have any pointers for what to do to use this feature?

bill.yu
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Re: 6-mic array using GPIO clock

Post by bill.yu » Wed Jun 05, 2019 4:46 pm

Hi there,

here is the schematic related with mclk_en. thanks.

Image

Image

colin.dente
Pre-kindergarten
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Re: 6-mic array using GPIO clock

Post by colin.dente » Mon Jun 10, 2019 8:35 pm

Thanks for that Bill.

I think that the 2520 type oscillator sets its output to high impedance when enable is low, so I should be able to put in the missing link, drive MCLK_EN low, and then drive GCLK from the Pi. My only question is whether a 24MHz clock is feasible to send over the GPIO connector. I know that the AC108 has many possible input clocks. Could you advise on how to program its PLL for a lower frequency clock input?

Colin

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