Parameter changing ADAU1701

rastariot Question

Nov 4, 2010 00:00

Hi all,

I am new to sigmaDSPs and I have a question regarding parameter changing without SigmaStudio. Let´s take for example a simple three band EQ.

I can follow the changings in the capture window and could get these infos to feed the microcontroller which in turn communicates with the DSP via I2C.

This is an excerpt of the capture window:

Safeload Write ParamName: EQ1940Single20B1 Param Value: 1.91170489788055

Safeload Write Param Name: EQ1940Single21B1 Param Value: -3.23407685756683

Safeload Write Param Name: EQ1940Single22B1 Param Value: 1.40179359912872

Safeload Write Param Name: EQ1940Single21A1 Param Value: 1.56372106075287

Safeload Write Param Name: EQ1940Single22A1 Param Value: -0.643142700195313

Maybe I missed some documents, but I really have no idea how I could calc my own coefficients for let´s say changing from peak to shelving or simply to move the corner frequency - just getting this capture info above. Is there any more documentation regarding the internal filter structures? Or is my approach or thinking wrong?

Please help.

best,

rastariot

Audio Signal Processors

i2c

microcontroller

sigmastudio

SigmaDSP Audio Processors

adau1701

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ADIApproved Reply

Nov 4, 2010 00:00

The SigmaStudio help documentation includes the equations that are used to calculate the filter coefficients. You can find these equations under Algorithm Information > EQ.

SigmaStudio also includes a tool for generating tables of filter coefficients. Under the Tools menu, there is a filter table generator that you can use to generate coefficients for a range of filters, such as 31 peaking EQ filters with a center frequency of 1000 Hz, at a boost setting of +15 to -15 dB in 1 dB steps.

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rastariot Reply

Nov 5, 2010 00:00

Hi JeradL,

thanks for your reply. Meanwhile I´ve found the info you are referring to in the sigmaStudio help.

It´s just a little confusing that the coefficient a0,a1,a2 and b0, b1, b2 are named 0A1,1A1,2A1 and so far. At least at the first glance.

so from my orginal post:

EQ1940Single21B1 would be B1 and

EQ1940Single22B1 would be B2 and so on, right?

As I want to change the parameters on the fly I needed the formulas to calc on PC, but these infos I have now.

Thanks very much for your help!

best,

rastariot

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rastariot Reply

Nov 5, 2010 00:00

Thanks for clarifying this!

best,

rastariot

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ADIApproved Reply

Nov 5, 2010 00:00

rastariot wrote:

so from my orginal post:

EQ1940Single21B1 would be B1 and

EQ1940Single22B1 would be B2 and so on, right?

Yes, this is correct. The digit at the end of the parameter name is used to enumerate multiple filters which share the same base name. The coefficient name b1, b2, etc. is saved as 1B, 2B, etc. to avoid naming confusion when there are >10 enumerated filters.