FIR filter on ADAU 1701

Question

I'm working on a project where I need to isolate a sound signal with a frequency range of 20-40kHz while filtering out unwanted low-frequency noise. To achieve this, I'm using a highly sensitive microphone to capture the noise and an ADAU 1701 programmer board equipped with a FIR filter. However, I'm encountering an issue where the DSP seems to be incapable of processing frequencies above 20 kHz. I'm unsure whether this limitation stems from the ADAU 1701, sigma studio schematic or the developer board. Could someone offer suggestions on how to address this problem? 
 This is the developer board I am using: www.tinysineaudio.com/.../tsa1701-audio-dsp-board

KJBob · Accepted Answer

Hello, 
 To handle a frequency range up to 40 KHz, set your ADAU1701 to operate a a sample rate of 96 KHz. Often this can be done without any hardware mods -- thus it should be possible with the board you have. You'll need to make two adjustments within SigmaStudio -- one in the Schematic window, the other in the HW Configuration / 170x Register Control window. The needed adjustments are described in this document: How do I change the sample rate of my SigmaStudio system? 
 Note that when running at 96K, your -1701 has less computation time between samples. This limits your project's size to approx. 500 instructions instead of the 1000 available at 48K. If your desired FIR filter uses too many instructions, you could try the Nth-order IIR filter. 
 Best regards, 
 Bob)

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FIR filter on ADAU 1701