int fix_fft(int16_t iq[], int m)
/* interleaved iq[], 0 <= n < 2**m, changes in place */
{
int mr, nn, i, j, l, k, istep, n, shift;
int16_t qr, qi, tr, ti, wr, wi;
n = 1 << m;
if (n > N_WAVE)
{return -1;}
mr = 0;
nn = n - 1;
/* decimation in time - re-order data */
for (m=1; m<=nn; ++m) {
l = n;
do
{l >>= 1;}
while (mr+l > nn);
mr = (mr & (l-1)) + l;
if (mr <= m)
{continue;}
// real = 2*m, imag = 2*m+1
tr = iq[2*m];
iq[2*m] = iq[2*mr];
iq[2*mr] = tr;
ti = iq[2*m+1];
iq[2*m+1] = iq[2*mr+1];
iq[2*mr+1] = ti;
}
l = 1;
k = LOG2_N_WAVE-1;
while (l < n) {
shift = 1;
istep = l << 1;
for (m=0; m<l; ++m) {
j = m << k;
wr = Sinewave[j+N_WAVE/4];
wi = -Sinewave[j];
if (shift) {
wr >>= 1; wi >>= 1;}
for (i=m; i<n; i+=istep) {
j = i + l;
tr = FIX_MPY(wr,iq[2*j]) - FIX_MPY(wi,iq[2*j+1]);
ti = FIX_MPY(wr,iq[2*j+1]) + FIX_MPY(wi,iq[2*j]);
qr = iq[2*i];
qi = iq[2*i+1];
if (shift) {
qr >>= 1; qi >>= 1;}
iq[2*j] = qr - tr;
iq[2*j+1] = qi - ti;
iq[2*i] = qr + tr;
iq[2*i+1] = qi + ti;
}
}
--k;
l = istep;
}
return 0;
}
void operation(int16_t* x,int16_t* y, int16_t* z, int N){
int i;
for (i=0; i<N; i+=8){
z[i] = FIX_MPY(x[i], y[i]);
z[i+1] = FIX_MPY(x[i+1], y[i+1]);
z[i+2] = FIX_MPY(x[i+2], y[i+2]);
z[i+3] = FIX_MPY(x[i+3], y[i+3]);
z[i+4] = FIX_MPY(x[i+4], y[i+4]);
z[i+5] = FIX_MPY(x[i+5], y[i+5]);
z[i+6] = FIX_MPY(x[i+6], y[i+6]);
z[i+7] = FIX_MPY(x[i+7], y[i+7]);
}
}
/*
fix_dot() - dot product of two fixed arrays
*/
fixed fix_dot(fixed *hpa, fixed *pb, int n)
{
fixed *pa;
long sum;
register fixed a,b;
unsigned int seg,off;
sum = 0L;
while(n--) {
a = *pa++;
b = *pb++;
FIX_MPY(a,a,b);
sum += a;
}
if(sum > 0x7FFF)
sum = 0x7FFF;
else if(sum < -0x7FFF)
sum = -0x7FFF;
return (fixed)sum;
}
/*
fix_mpy() - fixed-point multiplication
*/
fixed fix_mpy(fixed a, fixed b)
{
FIX_MPY(a,a,b);
return a;
}
