I have a small program where I use some of the functions from the TMS320C54x DSPLIB

version 1.0.

I have a input time series ( in TestData, a 512 point array ), but when I run trough the code

using Code Composer Simulator, it looks like the output from the FFT function is chancing.

It should have given the same output everytime, since the input time series is the same.

Here is my code:

void main(void)

{

while(1)
    {
    NQ2;
    P=N/2;

/***** Convert test input series from float to q15 *****/
fltoq15(TestData,(short *)SampleArray,N);

/* Bit reversal */

cbrev((short *)SampleArray,(short *)SampleArray,P);

/* Foward FFT */

rfft((short *)SampleArray,512,0);

/* Bit reversal before invers FFT */

cbrev((short *)SampleArray,(short *)SampleArray,P);

}
}

If I remove the last line in the code ( call to cbrev function ), the output from the FFT does not

change.

So, I do not understand why the second cbrev() function call should influence on the FFT function

( I look on the contents of SampleArray after rfft() and before cbrev() ).

Do anyone know what the problem could be ?

Best regards

Torgeir Jakobsen

e-mail: t...@aanderaa.no