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This version (08 Aug 2018 07:15) was approved by Venkatesan Krishnamoorthy.The Previously approved version (29 Nov 2016 11:16) is available.

General Eq (2nd order) Slew -(ADAU145x)

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The General (2nd-Order) filter is a variant of a second order bi quad filter which enables smooth transition of the filter parameters when filter parameters are changed, this is done by slewing from the current filter parameters(coefficients) to the one being set. The slewing takes place approximately in the time set by the user in the GUI. The slew time can be entered in the GUI slew Text box, or open the filter control window by clicking on the icon button and enter the slew time in the slew text box or by using the slew slider. The slew time range is limited between (0 to 1 second).
Slew function:
$lambda= e^{-1/{timeconstant*F_s}}$
Current Coefficient= Current Coffcicient* lambda + Target Coefficient * (1-lambda)

The above slewing function implements RC slewing. The parameter lambda is calculated based on the slewing time constant. The computations for slewing of filter coefficients is done on the DSP. The slew computation is always performed in single precision.

To open the filter control window, click on the icon button: Select the desired filter type from the drop-down combo-box list. The filter controls and the icon button image will change to reflect the selected filter type.

Configuration

GUI Control Name	Default Value	Range	Function Description
Enable/Bypass	Enabled	True/False	Enabling or disabling of filter. On bypass, the input signal is passed through without any processing.
Phase	In-Phase	True/False	Enabling the button, will invert the filter phase.
Frequency	1000 Hz	0 - 96k Hz	Center frequency of the filter
Slew	0s	0 - 1 seconds	Set the time to slew from one set of coefficients to another.

This block gives access to a wide variety of 2nd-order (biquad)filter algorithms. The blend factor can be entered(0-1) or changed using the slider. The Slew time can be entered in seconds (0-1) to slew from the initial blend factor to the target value. The available filter types are:

Parametric
Shelving
General High-Pass
General Low-Pass
General Band-Pass
General Band-Stop
Butterworth Low-Pass / High-Pass
Bessel Low-Pass / High-Pass
Tone Control
IIR Coefficient (direct coefficient entry)
1st-Order Low-Pass / High-Pass
All-pass
Peaking
Notch
Chebyshev Low-Pass / High-Pass

Shelving

GUI Control Name	Default Value	Range	Function Description
Shelf type	Low Shelf	Low Shelf/High Shelf	Shelving type for the filter
Frequency	1000Hz	0-96kHz	Cut off frequency of the filter
Gain	0dB	-15 - 15 dB	dB gain of the filter coefficients
Q	1.41	0-16	Q Factor for filter calculations
Slope	1	0-2	Slope

General

GUI Control Name	Default Value	Range	Function Description
Type	Low Pass Filter	Low Pass/High Pass/BandPass/BandStop	General filter type
Frequency	1000Hz	0-96kHz	Cut off frequency of the filter
Gain	0dB	-15 - 15 dB	dB gain of the filter coefficients
Q	1.41	0-16	Q Factor for filter calculations

Butterworth/Bessel

GUI Control Name	Default Value	Range	Function Description
Type	Bessel Low Pass	Bessel Low Pass/Bessel High Pass/Butterworth Low Pass/Butterworth High Pass	Filter type
Frequency	1000Hz	0-96kHz	Cut off frequency of the filter
Gain	0dB	-15 - 15 dB	dB gain of the filter coefficients

Tone Control

GUI Control Name	Default Value	Range	Function Description
Treble Frequency	1000Hz	0-96kHz	Treble Cut off frequency of the filter
Treble Gain	0dB	-15 - 15 dB	Treble dB gain of the filter coefficients
Bass Frequency	1000Hz	0-96kHz	Bass Cut off frequency of the filter
Bass Gain	0dB	-15 - 15 dB	Bass dB gain of the filter coefficients

IIR Coefficient

GUI Control Name	Default Value	Range	Function Description
b0	1	-100 to 100	B0 coefficient for the filter
b1	0	-100 to 100	B1 coefficient for the filter
b2	0	-100 to 100	B2 coefficient for the filter
a1	0	-100 to 100	A1 coefficient for the filter
a2	0	-100 to 100	A2 coefficient for the filter

First Order Filters

GUI Control Name	Default Value	Range	Function Description
Filter Frequency	1000Hz	0-96kHz	Cut off frequency of the filter
Active	Checked	Checked/Unchecked	Indicates whether the filter is active
Type	High for 1st filter,Low - for second filter	Low/High/All pass	Type of the filter
Gain	0dB	-15 - 15 dB	dB gain of the filter coefficients
Q	1.41	0-16	Q Factor for filter calculations

All Pass,Peaking,Notch

GUI Control Name	Default Value	Range	Function Description
Frequency	1000Hz	0-96kHz	Cut off frequency of the filter
Gain	0dB	-15 - 15 dB	dB gain of the filter coefficients
Q	1.41	0-16	Q Factor for filter calculations

Chebyshev

GUI Control Name	Default Value	Range	Function Description
Frequency	1000Hz	0-96kHz	Cut off frequency of the filter
Gain	0dB	-15 - 15 dB	dB gain of the filter coefficients
Ripple	0.1	0-10	Ripple Factor for filter calculations

DSP Parameter Information

GUI Control Name	Compiler Name	Function Description
Targ_B2_	EQS300MultiSpSlewAlg1Targ_B2_1	Bi-quad filter coefficient B2 for filter 1
Targ_B1_	EQS300MultiSpSlewAlg1Targ_B1_1	Bi-quad filter coefficient B1 for filter 1
Targ_B0_	EQS300MultiSpSlewAlg1Targ_B0_1	Bi-quad filter coefficient B0 for filter 1
Targ_A2_	EQS300MultiSpSlewAlg1Targ_A2_1	Bi-quad filter coefficient A2 for filter 1
Targ_A1_	EQS300MultiSpSlewAlg1Targ_A1_1	Bi-quad filter coefficient A1 for filter 1
lambda_	EQS300MultiSpSlewAlg1lambda_1	Bi-quad Slewing parameter lambda

Here,

Green - Algorithm Name
Red - Instance Number (Changes for each instance)
Blue - Parameter Name
Brown - Stage number

Supported ICs

ADAU145x

NOTE: Due to fixed point operations, the filter coefficients do not slew exactly in the set slew time.

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General Eq (2nd order) Slew -(ADAU145x)