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How to calculate an RMS table values to select filter curves?

SigmaDSP & SigmaStudio Paulo Aug 19, 2010 00:00 2 replies Original on forum ↗
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Paulo Question
Aug 19, 2010 00:00

Hi,

I am a beginner in Sigma DSP, using the ADAU1701 chip at MINIZ eval board.

In my application, i have an filter with about 31 curves, then i need to select the curves trough the auxiliary ADC (by potentiometer) and a Lockup table.

The first four points are below, but i need to calculate more points... How to calculate more values for my table?

0
1.19209289550781E-07
2.38418579101562E-07
3.57627868652343E-07

See the attached image for block schematic of my app.

Thanks!

Paulo

BrettG Reply
Aug 19, 2010 00:00

The calculation of index values is described in application note AN-951, which is available here:

http://www.analog.com/static/imported-files/application_notes/AN-951.pdf

On page 11 you can find the formula for converting 28.0 index values to 5.23 values stored in RAM.

Just for everybody's reference, I've listed the first 50 index points in the table below.

bbd1d23e45ac4de6ab80626b67066c5f.jpg
bbd1d23e45ac4de6ab80626b67066c5f.jpg
bbd1d23e45ac4de6ab80626b67066c5f.jpg-134x32.jpg
bbd1d23e45ac4de6ab80626b67066c5f.jpg-134x32.jpg
Paulo Reply
Aug 21, 2010 00:00

Thanks BrettG!

Now the filter are operating as I expect.

On my project I will use three potentiometer controlled filters (one LPF, one HPF and one Peak Filter)

Thanks for your assistance.

Paulo