ADAU1787 FDSP filter design on SigmaStudio

Hi,

I am having a problem on configuring filter for ADAU1787 FDSP on SigmaStudio. I set up the sampling rate of FDSP to 768kHz and SigmaDSP to 48kHz. In SigmaStudio, I configured 2nd-order butterworth LPF with cutoff frequency of 1kHz on FDSP, and then apply the filter to white noise source on FDSP. I recorded output signal via SAI, but I found the output signal was lowpass-filtered by 16kHz (1kHz x 16), not by 1kHz.

It seems like SigmaStudio configured FDSP filter with SDSP sampling rate of 48kHz. i.e. 1kHz cutoff was translated to normalized freguency of 1/(48*0.5), not 1/(768*0.5).

Is it an known issue? I would appreciate the feedback

Thanks.

ADAU1787

Integrated/Special Purpose A/D Converters

Audio CODECs