Analog Devices VISUALDSP++ 3.5 Manual page 474

DSP Run-Time Library Reference
#define fir_init(state, coeffs, delay, ncoeffs. index)
(state).h = (coeffs);
(state).d = (delay);
(state).p = (delay);
(state).k = (ncoeffs); \
(state).l = (index)
The characteristics of the filter (passband, stopband, and so on) are depen-
dent upon the number of filter coefficients and their values. A pointer to
the coefficients should be stored in
number of coefficients.
Each filter should have its own delay line which is a vector of type
and whose length is equal to the number of coefficients. The vector should
be initially cleared to zero and should not otherwise be modified by the
user program. The structure member
delay line, and the function uses
within the vector.
The structure member
mally set to an interpolation/decimation index before calling either the
fir_interp_fr16
Algorithm
k − 1
∑
=
i y ) ( h ( j * )
=
j 0
Domain
-1.0 to +1.0
4-58
\
\
\
s->p
is not used by
s->l
or
fir_decima_fr16
=
i x ( - j ) for i 0 1 , ,...
VisualDSP++ 3.5 C/C++ Compiler and Library Manual
, and should be set to the
s->h s->k
should be set to the start of the
s->d
to keep track of its current position
. This field is nor-
fir_fr16
functions.
−
n 1
for ADSP-219x DSPs
\
fract16