AnsweredAssumed Answered

Problem with FIR filter frequency cut and sampling frequency

Question asked by Arthur68 on May 31, 2013
Latest reply on Jun 10, 2013 by Arthur68

Hello everyone,

 

I'm quite new with DSP programming, so here is my problem :

I have an EVAL-ADAU1761Z and I am using SigmaStudio. What I wish to do is to use 7th order filters (so the only solution is to use FIR filters, am I right ?).

I design my filters using WinFilter (a free filter designer soft) and when designing one, I can change the sampling frequency of the filter. This will have a direct impact on the frequency cut of the filter in SigmaStudio. Once my filter is done I export all my coefficients and enter them in the table of my FIR filter bloc.

The thing is that I don't need to use a sampling rate over 12kHz or 11kHz, so when designing my filters I enter 12kHz for the sampling frequency but once in SigmaStudio the frequency cut of the filter has changed (is higher) because the DSP works at 48kHz. I've tried to change all the sampling rates I could find in SigmaStudio : in Hardware Configuration DSP setup and DSP Registers, but no way to make the frequency cut match with the one in the filter design software (the frequency cut doesn't even change when I change the sampling frequencies).

So I would like to know if you can change the internal sampling rate of the DSP or if it's just fixed at 48kHz, or if the frequency really change but it's another problem with the filter...

 

Thanks in advance for your answers !

 

Arthur

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