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Problem with IIR Filter for Blackfin

Question asked by rafaelwerneck0 on Jan 12, 2011
Latest reply on Jan 27, 2011 by rafaelwerneck0

Hello

 

I'm implementing one IIR Elliptical filter for Blackfin (BF-518), but the output of the filter does not agree with what I expected.

 

My input is a waveform of 60 Hz (Amplitude = 0.8) 600Hz 720Hz 840Hz 960Hz (Amplitude = 0.08)

 

 

1.JPG

 

 

The filter coefficients were generated by MATLAB.  The cutoff frequency is 500Hz and the sampling frquency is 61440Hz:

 

"[B, A] = ELLIP (4,3,40,500 / 30,720).

 

Running the filter library "iirdf1_fr16" I get the following waveform at the filter output:

 

2.JPG

 

 

I would like a help because I do not understand why this occurs.

 

The project files are attached.

 

Thank you.

 

Rafael.

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