MCU/DSP Combination

Good Day,

I have an application where I have to run a 2048 or a 4096 points FFT
every 30 seconds. I am wondering whether I can accomplish this with a
regular microcontroller since my timing requirements are not that
stringent. It is not greatly important whether the FFT is integer or
floating point, the values are 16 bit A/D values. I was considering
just using a plain old TI-MSP 430 with 10K or RAM.
Does anyone have a better suggestion as far as ease of implementation,
low power and price?

Thank you.

fulan wrote:
> Good Day,
>
> I have an application where I have to run a 2048 or a 4096 points FFT
> every 30 seconds. I am wondering whether I can accomplish this with a
> regular microcontroller since my timing requirements are not that
> stringent. It is not greatly important whether the FFT is integer or
> floating point, the values are 16 bit A/D values. I was considering
> just using a plain old TI-MSP 430 with 10K or RAM.
> Does anyone have a better suggestion as far as ease of implementation,
> low power and price?

Since that is at the top-end of MSP430, I'd also look at the bottom-end
of the many ARM Flash uC recently appearing.
Philips LPC2xxx family would be a good place to start, but you could
define more peripherals, and that would focus your choice more.
AnalogDevices, Atmel, Intel, Motorola, Philips, ST are all busy
announcing/ramping ARM single chip uC in various market segments.
-jg

Did you look into the PXA800F from Intel? It has a MCU and DSP built
into the same chip.

Sandeep
--
http://www.EventHelix.com/EventStudio
EventStudio 2.0 - System Architecture Design CASE Tool

fulan wrote:
>
> Good Day,
>
> I have an application where I have to run a 2048 or a 4096 points FFT
> every 30 seconds. I am wondering whether I can accomplish this with a
> regular microcontroller since my timing requirements are not that
> stringent. It is not greatly important whether the FFT is integer or
> floating point, the values are 16 bit A/D values. I was considering
> just using a plain old TI-MSP 430 with 10K or RAM.

I suggest getting a portable C implementation and trying it on the
MSP430. I haven't tried it, but if your processor has the built-in
multiply and you use a sine lookup table, I suspect it will do the
transform in a few seconds, under you 30 second allotment.

Thad

(fulan) writes:
>
> I have an application where I have to run a 2048 or a 4096 points FFT
> every 30 seconds. I am wondering whether I can accomplish this with a
> regular microcontroller since my timing requirements are not that
> stringent. It is not greatly important whether the FFT is integer or
> floating point, the values are 16 bit A/D values. I was considering
> just using a plain old TI-MSP 430 with 10K or RAM.

Your first problem with doing an FFT is data space. A 4K
transform is going to need at least 16 Kbytes for even a
single-precision float form. This won't fit well in 10
Kbytes of RAM.

> Does anyone have a better suggestion as far as ease of implementation,
> low power and price?

(Everett M. Greene) wrote in message news:<>...
> (fulan) writes:
> >
> > I have an application where I have to run a 2048 or a 4096 points FFT
> > every 30 seconds. I am wondering whether I can accomplish this with a
> > regular microcontroller since my timing requirements are not that
> > stringent. It is not greatly important whether the FFT is integer or
> > floating point, the values are 16 bit A/D values. I was considering
> > just using a plain old TI-MSP 430 with 10K or RAM.
>
> Your first problem with doing an FFT is data space. A 4K
> transform is going to need at least 16 Kbytes for even a
> single-precision float form. This won't fit well in 10
> Kbytes of RAM.
>
> > Does anyone have a better suggestion as far as ease of implementation,
> > low power and price?

Hi,

using the LPC2105 or LPC2106 from Philips with 32 / 64k RAM would
definitely be an easier implementation than trying it with a 10k MSP
430. However, if stand-by current is an issue (battery driven?) you
might want to try the MSP430 as I consider it best in class for
stand-by. Looking at Mips/Watt I would think the ARM devices can
actually easily compete.

Cheers, Bob

There are at least a couple of "combo" series available, maybe more.
Look at Motorola's DSP56F800 product line, and Microchip's "dsPIC"
product line.

(fulan) wrote:

>Good Day,
>
>I have an application where I have to run a 2048 or a 4096 points FFT
>every 30 seconds. I am wondering whether I can accomplish this with a
>regular microcontroller since my timing requirements are not that
>stringent. It is not greatly important whether the FFT is integer or
>floating point, the values are 16 bit A/D values. I was considering
>just using a plain old TI-MSP 430 with 10K or RAM.
>Does anyone have a better suggestion as far as ease of implementation,
>low power and price?
>
>Thank you.


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On 14 Jun 2004 16:20:09 GMT, Brian Aase <> wrote:

>There are at least a couple of "combo" series available, maybe more.
>Look at Motorola's DSP56F800 product line, and Microchip's "dsPIC"
>product line.

I guess it depends on how you define "combo" - Those listed above
and the lower-end TI, Motorola (and I presume AD) DSP's are basically
DSP cores with embedded peripherals added on-chip, and perhaps also
advertised with extra "embedded instructions" for fast bit twiddling.
There seem to be many of them around, so perhaps these should have a
different name to distinguish them from plain-vanilla high-end DSP's.
Maybe it should be called a "Digital Signal Microcontroller." or DSM
A DSM has a MAC and instructions to use it, as well as the features
of microcontrollers (data RAM, program ROM, I/O ports) so that it can
be made into an operational computer (with "DSP capabilities") with
only a small addition of external passive components.
The distinction between microprocessor and microcontroller was made
many years (decades?) ago (who did it? Was it Motorola with the
68HC11, or maybe Intel's 8048?). DSM's have grown in popularity
without being distinguished from the original DSP's.

Zilog had (and may still have) a "true" combo of both a
microcontroller and a separate DSP on one piece of silicon, with
various ports so they can communicate with and (presumably) interrupt
each other. I haven't heard of any other such device.

> (fulan) wrote:
>
>>Good Day,
>>
>>I have an application where I have to run a 2048 or a 4096 points FFT
>>every 30 seconds. I am wondering whether I can accomplish this with a
>>regular microcontroller since my timing requirements are not that
>>stringent. It is not greatly important whether the FFT is integer or
>>floating point, the values are 16 bit A/D values. I was considering
>>just using a plain old TI-MSP 430 with 10K or RAM.
>>Does anyone have a better suggestion as far as ease of implementation,
>>low power and price?
>>
>>Thank you.
>
>
>_________________________________________________ ______________________________
>Posted Via Uncensored-News.Com - Accounts Starting At $6.95 - http://www.uncensored-news.com
> <><><><><><><> The Worlds Uncensored News Source <><><><><><><><>
>

-----
http://mindspring.com/~benbradley

Ben Bradley wrote:
> On 14 Jun 2004 16:20:09 GMT, Brian Aase <> wrote:
>
>
>>There are at least a couple of "combo" series available, maybe more.
>>Look at Motorola's DSP56F800 product line, and Microchip's "dsPIC"
>>product line.
>
>
> I guess it depends on how you define "combo" - Those listed above
> and the lower-end TI, Motorola (and I presume AD) DSP's are basically
> DSP cores with embedded peripherals added on-chip, and perhaps also
> advertised with extra "embedded instructions" for fast bit twiddling.
> There seem to be many of them around, so perhaps these should have a
> different name to distinguish them from plain-vanilla high-end DSP's.
> Maybe it should be called a "Digital Signal Microcontroller." or DSM
> A DSM has a MAC and instructions to use it, as well as the features
> of microcontrollers (data RAM, program ROM, I/O ports) so that it can
> be made into an operational computer (with "DSP capabilities") with
> only a small addition of external passive components.
> The distinction between microprocessor and microcontroller was made
> many years (decades?) ago (who did it? Was it Motorola with the
> 68HC11, or maybe Intel's 8048?). DSM's have grown in popularity
> without being distinguished from the original DSP's.

Good point, Motorola even tries the strange label of 'hybrid', which
does not gel well in a industry that already knows what hybrid means.
I give dsPIC a higher name selection score.

>
> Zilog had (and may still have) a "true" combo of both a
> microcontroller and a separate DSP on one piece of silicon, with
> various ports so they can communicate with and (presumably) interrupt
> each other. I haven't heard of any other such device.

There are quite a few at the top-end, where DSP+ARM is now almost the
default for certain cell phone engines, tho these are not single-die
system solutions in the way a microcontroller is.
-jg

Thank you for the many replies.

My specs dictate that I have a 14-16bit ADC converter, this can be
internal to the processor or external. The requirement is the ability
to read at least 256 samples per second, ideally 512 samples per
second. We would repeat the reading for approximately 8 seconds and
perform some FFTs on the data. The philips LPC2106 seems like a good
option however it lacks an internal A/D. Furthermore, are their A/D
converters capable of acquiring that many points at that resolution
that quickly?(internal or external).

Moussa

(Schwob) wrote in message news:<. com>...
> (Everett M. Greene) wrote in message news:<>...
> > (fulan) writes:
> > >
> > > I have an application where I have to run a 2048 or a 4096 points FFT
> > > every 30 seconds. I am wondering whether I can accomplish this with a
> > > regular microcontroller since my timing requirements are not that
> > > stringent. It is not greatly important whether the FFT is integer or
> > > floating point, the values are 16 bit A/D values. I was considering
> > > just using a plain old TI-MSP 430 with 10K or RAM.
> >
> > Your first problem with doing an FFT is data space. A 4K
> > transform is going to need at least 16 Kbytes for even a
> > single-precision float form. This won't fit well in 10
> > Kbytes of RAM.
> >
> > > Does anyone have a better suggestion as far as ease of implementation,
> > > low power and price?
>
> Hi,
>
> using the LPC2105 or LPC2106 from Philips with 32 / 64k RAM would
> definitely be an easier implementation than trying it with a 10k MSP
> 430. However, if stand-by current is an issue (battery driven?) you
> might want to try the MSP430 as I consider it best in class for
> stand-by. Looking at Mips/Watt I would think the ARM devices can
> actually easily compete.
>
> Cheers, Bob