DSP_fft
x0r = x[2*(i + 0) | + 0]; | x0i = x[2*(i + 0) | + 1]; | ||
x1r = x[2*(i + 1) | + 0]; | x1i = x[2*(i + 1) | + 1]; | ||
x2r = x[2*(i + | 2) | + 0]; | x2i = x[2*(i + | 2) | + 1]; |
x3r = x[2*(i + | 3) | + 0]; | x3i = x[2*(i + | 3) | + 1]; |
/* −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−− */
/* Calculate the final FFT result from this butterfly.*/
/* −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−− */
y0r = (x0r + x2r) + (x1r + x3r); y0i = (x0i + x2i) + (x1i + x3i); y1r = (x0r − x2r) + (x1i − x3i); y1i = (x0i − x2i) − (x1r − x3r); y2r = (x0r + x2r) − (x1r + x3r); y2i = (x0i + x2i) − (x1i + x3i); y3r = (x0r − x2r) − (x1i − x3i);
y3i = (x0i − x2i) + (x1r − x3r);
/* −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−− */
/* | Digit reverse our address to convert the digit−reversed input | */ |
/* | into a linearized output order. This actually results in a | */ |
/* | digit−reversed store pattern since we’re loading linearly, but | */ |
/* | the end result is that the FFT bins are in linear order. | */ |
/* −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−− */
DIG_REV(i, m, j); /* Note: Result is assigned to ’j’ by the macro. */
/* −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−− */
/* Store out the final FFT results.*/
/* −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−− */
y[2*(j + | 0) | + 0] | = y0r; | y[2*(j + | 0) | + 1] | = y0i; | ||
y[2*(j + | s) + 0] | = y1r; | y[2*(j + | s) + 1] | = y1i; | ||||
y[2*(j + 2*s) | + | 0] | = y2r; | y[2*(j + 2*s) | + | 1] | = y2i; | ||
y[2*(j + 3*s) | + | 0] | = y3r; | y[2*(j + 3*s) | + | 1] | = y3i; | ||
}
}
C64x+ DSPLIB Reference |
|
