I'm planning to use FFTW library on the DSP....has
anybody used it with code composer studio to generate the coff file for
the DSP ??..please share your experiences
Reply by John Herman●November 20, 20052005-11-20
I woould suggest that you use the manufacturer's optimized FFT vice FFTW.
FFTW is designed for general purpose processors. The chip maker will have
special code that takes advantage of all the special hardware designed into
the DSP chip. FFTs execution speed is a major marketing number so all chip
vendors that I am aware put lots of effort into getting the best possible
speed. That code is frequently available for free and I believe that is true
for TI chips..
In article <firstname.lastname@example.org>, "bngguy"
> I'm planning to use FFTW library on the DSP....has
>anybody used it with code composer studio to generate the coff file for
>the DSP ??..please share your experiences
Reply by bngguy●November 22, 20052005-11-22
Thank your for your response.I'm using a TMS320C6713
based custom target board and for some reason the fft library / code i
downloaded from Texas instruments website doesn't work for more than 4k
points ....i'm looking at 16k points at the minimum...i would
appreciate any pointers in this direction.
Reply by Bhaskar Thiagarajan●November 22, 20052005-11-22
"bngguy" <email@example.com> wrote in message
> Hello John,
> Thank your for your response.I'm using a TMS320C6713
> based custom target board and for some reason the fft library / code i
> downloaded from Texas instruments website doesn't work for more than 4k
> points ....i'm looking at 16k points at the minimum...i would
> appreciate any pointers in this direction.
This is more than likely due to restrictions on internal memory (fast
memory) in that processor. The library may also be limiting your largest fft
size (again due to memory and/or architectural limitations). You could take
a speed penalty and get the library code to work on a larger fft size with
minimal changes to the library source (I'm sure this is available). Trying
to get fftw to work on a specialized DSP like the TI chip is not something
I'd recommend (although it is written in Ansi C and should technically work
well if your compiler is good enough).
Contact TI and see if they have modified versions of their library to
support larger FFT lengths.
Reply by John Herman●November 22, 20052005-11-22
Did you look at the code to determine why the FFT ssize is limited to 4096
points? I don't have the FFT source code for the 6713 and finding it on the
TI web site is not as easy (read damned near impossible) as it used to be.
The assembler is hard to read for DSPs in general and VLIW DSPs in particular.
Check to see if the limit is hardcode in a way that would allow you to change
that limit and recompile the code.
Sometimes, the FFT size is limited by the size of the internal twiddle factor
lookup table. You may need to provide your own for a larger FFT size so you
might check the assembler to see if it's required. The 6713 cache is large
enough (if you don't have the 6713B) to put that lookup table on the chip and
the data as well.