RE: [c6x] Re: Question about the FFT on C6711
Thanks for your help, Andrew.
But I try to divide my FFT into 4 FFTs with disabling the IT,
but the results were not good.
The results were only good when using the FFT
completely.
Can you help me on these several points ?
1. I wonder if the address of the factor's array is
always the same for all the calls of the small FFTs ?
Example : for N24 they always use &w[2*768] as
parameters of the 4 small FFTs ! Is it normal ?
2. In case of a number of complex points which is not a power
of 4, the n_min parameter is equal to 2 or 4 ?
3. If wonder if we always divide a large FFT into 4 small FFTs
? Example for N 48, can we divide into 8 small FFTs (of 256 points) or I am
obliged to divide into 4 small FFTs ?
Thanks,
Jean-Marc ROUXEL
-----Message d'origine-----
De : Andrew Elder [mailto:a...@bigfoot.com]
Envoye : mardi 16 janvier 2001 14:52
A : c...@egroups.com
Objet : [c6x] Re: Question about the FFT on C6711
Jean-Marc,
I have got it to work correctly in several steps. I divided a
1024 pt
FFT into 4 256 pt FFTs. It seemed to work fine.
The idea is that you can either run the FFT completely, or you
can
divide a large FFT into a number of small ones and then run
those.
BTW, fftspx_h is not interrupt safe. The way it uses the stack
is not
compatible with TI's C tools. The easiest fix is to
disable
interrupts around the entire call.
The following example is incorrect as well !
*
fftSPxSP_asm(512, &x_asm[0],&w[0],y_asm,brev,2,
0,512);
*
*
*
* is
equvalent
to:
*
*
*
*
fftSPxSP_asm(128, &x_asm[2*0],
&w[2*384],y_asm,brev,4,
0,512); *
*
fftSPxSP_asm(128, &x_asm[2*128],&w[2*384],y_asm,brev,4,
128,512); *
*
fftSPxSP_asm(128, &x_asm[2*256],&w[2*384],y_asm,brev,4,
256,512); *
*
fftSPxSP_asm(128, &x_asm[2*384],&w[2*384],y_asm,brev,4,
384,512); *
Andrew Elder
--- In c...@egroups.com, "Rouxel, Jeanmarc"
<jeanmarc.rouxel@a...>
wrote:
> Hello everybody,
>
> I'm implementing a FFT on a TMS320C6711.
>
> The code provided by TI (you can find it
at
> ftp://ftp.ti.com/pub/tms320bbs/c67xfiles/fftspx_h.asm)
realizes a
mixed
> radix FFT and will work as both as
> Radix-2 and Radix-4 FFT (for no of points of FFT as a
power of 2 or
4).
> Unfortunately the application note describing the code
has not been
finished
> yet.
>
> This algorithm allows the main fft of size N to be
divided into
several
> steps, allowing as much data reuse as possible.
>
> Has somebody tried to implement this algorithm with
several steps ?
I have
> some questions about the use of the factors.
>
> Thanks.
>
> Jean-Marc ROUXEL.
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