Looking for a DSP board to FFT

Looking for a DSP board to FFT

Post by Jorge Rapos » Thu, 16 Oct 1997 04:00:00



Hi!
I have an applicattion which requires a lot of sequencial 2-D FFT
sequential processing in small windows over hundrets of images. To speed
up the process I was considering using a DSP board (if possible with a
software library, so that I don't need to program the board). Can anyone
tell if such a board exists?

thanks
 Jorge

 
 
 

Looking for a DSP board to FFT

Post by Ray Andrak » Fri, 17 Oct 1997 04:00:00



> Hi!
> I have an applicattion which requires a lot of sequencial 2-D FFT
> sequential processing in small windows over hundrets of images. To speed
> up the process I was considering using a DSP board (if possible with a
> software library, so that I don't need to program the board). Can anyone
> tell if such a board exists?

> thanks
>  Jorge

Jorge,

depending on your speed requirements an FPGA based processor may be a
better option.  An FPGA is a Field Programmable Gate Array, which is a
programmable logic device containing a large array of logic blocks.
Each block is individually programmed to perform a fairly simple logic
function.  These blocks taken together can build a complex processor
that is customized to the task at hand.  An FFT processor built in an
FPGA will perform a 1024 point FFT in under 200 uS (this using an off
the shelf circuit design).

-Ray Andraka, P.E.
President, the Andraka Consulting Group, Inc.
401/884-7930     Fax 401/884-7950

http://users.ids.net/~randraka

 
 
 

Looking for a DSP board to FFT

Post by Richard Herveill » Fri, 17 Oct 1997 04:00:00




> > Hi!
> > I have an applicattion which requires a lot of sequencial 2-D FFT
> > sequential processing in small windows over hundrets of images. To speed
> > up the process I was considering using a DSP board (if possible with a
> > software library, so that I don't need to program the board). Can anyone
> > tell if such a board exists?

> > thanks
> >  Jorge
> Jorge,

> depending on your speed requirements an FPGA based processor may be a
> better option.  An FPGA is a Field Programmable Gate Array, which is a
> programmable logic device containing a large array of logic blocks.
> Each block is individually programmed to perform a fairly simple logic
> function.  These blocks taken together can build a complex processor
> that is customized to the task at hand.  An FFT processor built in an
> FPGA will perform a 1024 point FFT in under 200 uS (this using an off
> the shelf circuit design).

> -Ray Andraka, P.E.
> President, the Andraka Consulting Group, Inc.
> 401/884-7930     Fax 401/884-7950

> http://users.ids.net/~randraka

True, I checked out the DSP sources from Altera and they were real fast. But
the main disadvantage is the bitsize, if you have large numbers say (16?, 24
or 32) bit you probably need external memory or a FGPA with a lot of internal
memory (boy are they expensive). The FPGA has to control this memory (address
lines, strobe, data etc.). So you are probably building you own processor.
Don't do this, choose an existing processor.

On the other hand, if you have small numbers (up to 16 bit) and only a small
FFT and you don't want to do anything else, check out the FPGA's. All you need
is an FPGA, a serial PROM and an input, et voila there's you FFT.

Which solution is the best depends on your application. Try to determine what
you realy want. Do you want to do something concurently with your FFT, use a
DSP. Do you want to built a small fast FFT produkt choose FPGAs (or better an
of the shelf FFT ic). etc.etc.

good luck,
    Richard Herveille


 
 
 

Looking for a DSP board to FFT

Post by Ray Andrak » Fri, 17 Oct 1997 04:00:00



> True, I checked out the DSP sources from Altera and they were real fast. But
> the main disadvantage is the bitsize, if you have large numbers say (16?, 24
> or 32) bit you probably need external memory or a FGPA with a lot of internal
> memory (boy are they expensive). The FPGA has to control this memory (address
> lines, strobe, data etc.). So you are probably building you own processor.
> Don't do this, choose an existing processor.

Depends on the FPGA.  For Xilinx 4KE, for instance, the width is not
really an issue
However, depths greater than 32 start eating on chip resources.  Many of
the DSP designs I do use one or two external fast SRAMs (12ns or better)
for doing stuff that needs large amounts of memory.  A 12ns SRAM can be
accessed at better than 40 MHz with a -3 or -2 Xilinx part.  The
interface to the memory is usually very simple, consisting of an address
counter, I/O registers and very simple logic to create a write pulse.  I
believe the Xilinx 1024 point FFT uses internal storage only, and it
does the FFT in under 200uS. A more pipelined design will use more logic
but will get better performance. Marshall advertises a 4028EX-2HQ208 for
$401 in single quantities. Quantity and/or other customer discounts will
get you the parts at significantly lower prices.  -3 parts are less than
half the cost ($177 in same package).  These prices compare favorably
against specific purpose chips like the graychip, sharp butterfly and
LSI logic and obtain performance close to that of the dedicated chip
(and it blows the doors off a DSP microprocessor).  The FPGA also buys
you the flexibility to reuse the logic for something else when you do
not need to do FFTs.

Quote:> On the other hand, if you have small numbers (up to 16 bit) and only a small
> FFT and you don't want to do anything else, check out the FPGA's. All you need
> is an FPGA, a serial PROM and an input, et voila there's you FFT.

Performance does degrade with word width because of the carry chain used
for arithmetic operations.  Pipelining can regain the performance in
most cases by trading data rate for latency.

Quote:> Which solution is the best depends on your application. Try to determine what
> you realy want. Do you want to do something concurently with your FFT, use a
> DSP. Do you want to built a small fast FFT produkt choose FPGAs (or better an
> of the shelf FFT ic). etc.etc.

I think the issue is more of how fast you need to get something done.
If you have the time to wait for a DSP micro to clunk along to do your
FFT, by all means use it. You won't get the functionality at a lower
price.  However, many times the amount of processing required per sample
limits the maximum data rate through a DSP micro based processor to an
unacceptably low figure.  When that happens, one is forced to either use
custom hardware or multiple DSP micros.  The SRAM based FPGAs help to
bring the cost of custom hardware down and provide the flexibility
(reprogrammability) previously available only to the microprocessor
solutions.

-Ray Andraka, P.E.
President, the Andraka Consulting Group, Inc.
401/884-7930     Fax 401/884-7950

http://users.ids.net/~randraka

 
 
 

Looking for a DSP board to FFT

Post by Raymond E. Roger » Fri, 17 Oct 1997 04:00:00


I agree.  There are two companies selling IBM pc compatable boards
together with some software.  


or
<http://www.vcc.com>

Enjoy
Ray



> > Hi!
> > I have an applicattion which requires a lot of sequencial 2-D FFT
> > sequential processing in small windows over hundrets of images. To speed
> > up the process I was considering using a DSP board (if possible with a
> > software library, so that I don't need to program the board). Can anyone
> > tell if such a board exists?

> > thanks
> >  Jorge
> Jorge,

> depending on your speed requirements an FPGA based processor may be a
> better option.  An FPGA is a Field Programmable Gate Array, which is a

 
 
 

Looking for a DSP board to FFT

Post by Chris Bo » Tue, 21 Oct 1997 04:00:00





>> > I have an applicattion which requires a lot of sequencial 2-D FFT
>> > sequential processing in small windows over hundrets of images. To speed
>> > up the process I was considering using a DSP board (if possible with a
>> > software library, so that I don't need to program the board). Can anyone
>> > tell if such a board exists?

The Lucent DSP32C has decent support in C language functions for FFT
processing with some function adapted to 2D FFT (for example a matrix
transpose function which swaps rows for columns which is helpful in
the 2nd pass of a 2D FFT). This was used in many products for image
processing, such as MRI imaging, where the image data needs a 2D FFT.
This would be a simple solution, though not the fastest - appropriate
if you wanted a PC based solution using a plug in board, and wanted a
simple life, but probably not otherwise. See details of the DSP32C on
our web page at:

        http://www.bores.com/dsp32c.htm

Also, our new XCWin software programs PC based DSP32C boards and
includes simple 2D image display routines. See details at:

        http://www.bores.com/xcwin.htm

A 2D FFT on an image size of 64 x 64 takes about 36 ms, maybe a little
less. A 2D FFT on a 512 x 512 image takes 6 seconds. A main benefit is
the library functions that allow the code to be quite concise.

Chris Bore
:-)
--
Chris Bore
BORES Signal Processing
Fordwater
Pond Road
Woking
Surrey GU22 0JZ
England

Tel: 01483 740138
Fax: 01483 740136

Web: http://www.bores.com

 
 
 

Looking for a DSP board to FFT

Post by Chris Bo » Tue, 21 Oct 1997 04:00:00



>> > I have an applicattion which requires a lot of sequencial 2-D FFT
>> > sequential processing in small windows over hundrets of images. To speed
>> > up the process I was considering using a DSP board (if possible with a
>> > software library, so that I don't need to program the board). Can anyone
>> > tell if such a board exists?

The DSP32C was much used for 2D image processing. Particularly in
medical image reconstroction from scanners using MRI. PC boards are
used for this.

The C compiler includes FFT functions, also a matrix transposition
(swapping rows for columns) which is helpful in the second pass of a
2D FFT.

A 64 x 64 FFT takes about 36 ms (maybe a bit less).
A 512 x 512 FFT takes about 6 seconds.

The XCWin software has the FFT functions, programmable simply from C,
and some useful 2D image plotting functions - as gray scale or colour
VGA. Brief details are on our web page at:

        http://www.bores.com/xcwin.htm

Chris Bore
:-)
--
Chris Bore
BORES Signal Processing
Fordwater
Pond Road
Woking
Surrey GU22 0JZ
England

Tel: 01483 740138
Fax: 01483 740136

Web: http://www.bores.com

 
 
 

Looking for a DSP board to FFT

Post by Mark Cartlid » Wed, 22 Oct 1997 04:00:00


Take a look at our SMT311 FFT processor TIM. This can plug on to our
SMT320 PCI carrier.

On Thu, 16 Oct 1997 10:59:52 -0400, "Raymond E. Rogers"


>I agree.  There are two companies selling IBM pc compatable boards
>together with some software.  


>or
><http://www.vcc.com>

>Enjoy
>Ray



>> > Hi!
>> > I have an applicattion which requires a lot of sequencial 2-D FFT
>> > sequential processing in small windows over hundrets of images. To speed
>> > up the process I was considering using a DSP board (if possible with a
>> > software library, so that I don't need to program the board). Can anyone
>> > tell if such a board exists?

>> > thanks
>> >  Jorge
>> Jorge,

>> depending on your speed requirements an FPGA based processor may be a
>> better option.  An FPGA is a Field Programmable Gate Array, which is a

Mark Cartlidge

SUNDANCE MULTIPROCESSOR TECHNOLOGY LTD
Chiltern House, Waterside, Chesham, HP5 1PS, United Kingdom

Dir.:011-44-1494-793191        Tel:011-44-1494-793167           Fax:011-44-1494-793168

 
 
 

Looking for a DSP board to FFT

Post by Chris Bo » Fri, 24 Oct 1997 04:00:00



>The Lucent DSP32C has decent support in C language functions for FFT
>processing with some function adapted to 2D FFT
> ...
>A 2D FFT on an image size of 64 x 64 takes about 36 ms, maybe a little
>less. A 2D FFT on a 512 x 512 image takes 6 seconds. A main benefit is
>the library functions that allow the code to be quite concise.

Correction... the time for 512 x 512 2D FFT should read 0.6 seconds,
not 6 seconds. This is for a floating point 2D FFT.

Chris Bore
:-)
--
Chris Bore
BORES Signal Processing
Fordwater
Pond Road
Woking
Surrey GU22 0JZ
England

Tel: 01483 740138
Fax: 01483 740136

Web: http://www.bores.com

 
 
 

Looking for a DSP board to FFT

Post by Michael Rei » Fri, 24 Oct 1997 04:00:00



Quote:

>Also, our new XCWin software programs PC based DSP32C boards and
>includes simple 2D image display routines. See details at:

>        http://www.bores.com/xcwin.htm

>A 2D FFT on an image size of 64 x 64 takes about 36 ms, maybe a little
>less. A 2D FFT on a 512 x 512 image takes 6 seconds. A main benefit is
>the library functions that allow the code to be quite concise.

>Chris Bore
>:-)
>--

6 Seconds is pretty long! Without a DSP my 512 x 512
complex FFT writtenin C-builder uner win95 takes 3 secs
(on a low end pentium-100Mhz) while on a Pentium Pro 200
it takes a little over 0.5 secs!

Michael Reich

 
 
 

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