This version (18 May 2021 09:09) was approved by Nikhin Shetty.

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General First Order Filter


The General 1st-Order block allows you to design 1st-order lowpass and highpass filters.

Drag the block into the workspace and it's ready to use. As with other blocks, there's the option to increase the stage count to this algorithm. Observe, however, that with this module adding another stage the algorithm will add another frequency band to the block, which is equivalent to having two filters in series.

To switch among highpass, lowpass, and flat, click the filter type icon. This can be done in real time, without needing to recompile the project. Enter your desired values in the text fields to set the cutoff frequency and overall gain (sometimes called scale gain) of the filter. Or click the arrows to increment values for these parameters. To increment them very quickly, click and hold.

Calculating Filter Coefficients

Use the following formulas to calculate the coefficients for first order filters.


  • frequency = Cutoff frequency
  • gain = Linear Gain
  • fs = Sample Rate
  • PI = π

For lowpass filters,

  • A1 = 2.7^(-2 * PI * frequency/fs))
  • B0 = gain * (1.0 - A1)
  • B1 = 0

For highpass filters,

  • A1 = e^(-2 * PI * frequency/fs)) where e = 2.718…..
  • B1 = (1.0 + A1) * 0.5 * gain
  • B0 = -B1

For allpass filters,

  • A1 = 2.7^(-2 * PI * frequency/fs))
  • B0 = -gain * A1
  • B1 = gain

Targets Supported

Name ADSP-214xx ADSP-215xx/SC5xx ADAU145x/146x
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General First Order NA NA S



————————————— —————————— ————————————————
Input Audio Input channel


————————————— —————————— ————————————————
Output AudioFilter Output

Configurable Parameters

GUI Parameter NameDefault ValueRangeFunction Description
———————————————- —————————- ————————————- —————————————————————-
NumStages11 to 8Number of filter stages
Gain_StageX0-12 to 12 dBGain for individual filter stage
Frequency_StageX1000 1 to 96000Filter cutoff frequency of individual filter stage
FilterType_StageX0 0 to 2LowPass/HighPass/BandPass filter type of individual filter stage
Phase_StageXtrue true/falseIn phase/out of phase for individual filter stage
Enabled_StageXtrue true/falseFilter Enabled/Bypassed for individual filter stage

Note : _StageX - Refers to parameters of each stage. X represents the stage index.

DSP Parameters

Parameter Name Description ADAU145x/146x
——————————- ———————————————— —————————-
B0_StageXB0 Filter Coefficient8.24
B1_StageXB1 Filter Coefficient8.24
A1_StageXA1 Filter Coefficient8.24

Note: X- Stage Number (Changes for each stage coefficients)

resources/tools-software/sigmastudiov2/modules/filters/generalfirstorder.txt · Last modified: 12 May 2021 17:04 by Sreesha Y M