NAME

       biquad - Biquad IIR filter

SYNOPSIS

       loadrt biquad [count=N|names=name1[,name2...]]

DESCRIPTION

       Biquad IIR filter. Implements the following transfer function: H(z) = (n0 + n1z-1 + n2z-2)
       / (1+ d1z-1 + d2z-2)

FUNCTIONS

       biquad.N (requires a floating-point thread)

PINS

       biquad.N.in float in
              Filter input.

       biquad.N.out float out
              Filter output.

       biquad.N.enable bit in (default: 0)
              Filter enable. When false, the in  pin  is  passed  to  the  out  pin  without  any
              filtering.   A  transition  from  false  to  true  causes filter coefficients to be
              calculated according to the current type  and  the  describing  pin  and  parameter
              settings

       biquad.N.valid bit out (default: 0)
              When  false,  indicates  an  error  occurred  when  calculating filter coefficients
              (require 2>Q>0.5 and f0>sampleRate/2)

       biquad.N.type u32 in (default: 0)
              Filter type determines  the  type  of  filter  coefficients  calculated.   When  0,
              coefficients  must  be  loaded directly from the n0,n1,n2,d1 params.  When 1, a low
              pass filter is created specified by the f0,Q pins.   When  2,  a  notch  filter  is
              created specified by the f0,Q pins.

       biquad.N.f0 float in (default: 250.0)
              The corner frequency of the filter.

       biquad.N.Q float in (default: 0.7071)
              The Q of the filter.

       biquad.N.s1 float out (default: 0.0)
              1st-delayed internal state (for debug only)

       biquad.N.s2 float out (default: 0.0)
              2nd-delayed internal state (for debug only)

PARAMETERS

       biquad.N.d1 float rw (default: 0.0)
              1st-delayed denominator coef

       biquad.N.d2 float rw (default: 0.0)
              2nd-delayed denominator coef

       biquad.N.n0 float rw (default: 1.0)
              non-delayed numerator coef

       biquad.N.n1 float rw (default: 0.0)
              1st-delayed numerator coef

       biquad.N.n2 float rw (default: 0.0)
              2nd-delayed numerator coef

AUTHOR

       Peter G. Vavaroutsos

LICENSE

       GPL