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SigmaStudio: problem entering large b1 values for IIR filter

Question asked by SteveL on Sep 19, 2011
Latest reply on Sep 23, 2011 by SteveL



I'm on the very last section of the code for my current SigmaDSP project (using the ADAU1701) but have run into a problem when manually entering coefficient data for some IIR filters.


As I understand it, the coefficients are all in 5.23 format and can therefore have values up to (nearly) +/-16.000. However, I am unable to enter negative values larger than -5.000 into the b1 coefficient box - higher values are clipped to -5.000. The other coefficient boxes will all accept the full expected range, and b1 will accept larger positive numbers.


This occurs with both the index-slectable and fixed second-order filters and - of course - my filter needs a b1 value over -5.000.


Is this a quirk of SigmaStudio, or is there something special about b1 which I am not aware of? If the former, is there a workaround?


BTW, I saw that v3.4 of SigmaStudio claimed to fix an IIR Coefficient Window bug and hurriedly installed the upgrade, but it has made no difference.


Any help would be much appreciated!


Kind regards,


Steve L.