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ADAU1452 sampling frequency

Question asked by davker on Feb 23, 2017
Latest reply on Mar 24, 2017 by DaveThib

I'm working on ADAU1452miniZ board.
I took new project, and keep all default values. I just enabled SPDIF (through ASRC0) and SPDIF Out.
Master clock from oscillator is 12.288Mhz. PLL is set to /4 and then *96=> DSP system clock is 294.912MHz

I made following very simple schematics: just a FIR filter. I designed it to be bandpass (200Hz to 4kHz) @48kHz.
Input is SPDIF @48kHz.
If I set DSP sampling frequency at 48kHz=> OK I get expected frequency response (measured with Audio precision).
but if I increase DSP sampling frequency to 96k, measured frequency response of filter is unchanged (I expected it to be shifted by an octave).
I noticed that simulated value in Sigmastudio (using probe and stimulus) is correctly shifted.
I also noticed that sampling frequency on SPDIF output is always 48kHz, whatever selected DSP sampling frequency.
Shouldn't be same as DSP fs?

Can you help me to understand why DSP sampling frequency setting has no effect?

 

Thank you

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