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Multiple sampling rates ADAU1452

Question asked by Olombo on Jun 19, 2016
Latest reply on Jul 1, 2016 by Olombo



finally got my ADAU1452 Board working. Based on the community help without any hastle. worked directly everything fine.

Now a small questions regarding programming:

I want to use a FIR filter at low frequencies. In order to avoid large amount of coefficients (getting short on computing resources rapidly!) I want to resample the low frequency part (fs/4 or similar), compute with short FIR, resample to fs and send it out.


As far as I understoof I could do it like this:

ASRC input from e.g. I2S; resample to fs/4; send to DSP core

Compute it in DSP core; send to another ASRC

Resample in ASRC to fs; send to DSP Core

Use any output in DSP core


So although my internal fs is then e.g. 48kHz I will only have computed this signal every 4. sequence. Correct?

Is there anything to remember for the FIR filter? I shorten the tabs to 1/4 and adjust to new sample rate. But is that all? Will it accordingly only be called every 4. sample? Or is it still called every sample (and I have to make it 48kHz) and no computing resources are saved?


Hope my question is clear....