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MCU/DSP Combination

Discussion in 'Embedded' started by fulan, Jun 7, 2004.

  1. fulan

    fulan Guest

    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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  2. 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
     
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  3. 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
     
  4. Thad Smith

    Thad Smith Guest

    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
     
  5. (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?
     
  6. Schwob

    Schwob Guest

    (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
     
  7. Brian Aase

    Brian Aase Guest

    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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  8. Ben Bradley

    Ben Bradley Guest

    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
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    >


    -----
    http://mindspring.com/~benbradley
     
  9. 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
     
  10. fulan

    fulan Guest

    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:<>...
    > (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
     
  11. Jerry Avins

    Jerry Avins Guest

    fulan wrote:
    > 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).


    There are plenty of 16-bit audio D/A converters that sample 48,000 times
    a second. I don't know off hand of microcontrollers with internal ADCs
    wider than 12 bits, but I don't know much. I don't know what you intend
    to do with the data you collect, but be aware that many converter/-
    anti-alias filter combinations impose delays of many sample periods. I
    would call a sample rate below 1 KHz relatively slow.

    What do you mean by repeating the reading? You could mean acquiring a
    single string of 8 x 512 = 4096 contiguous samples and do one FFT, or
    else acquire 8 strings of 256 samples each, perhaps with caps between
    them, and doing 8 shorter FFTs, presumably averaging the results. Since
    the FFT gives cosine and sine (or real and imaginary, as you please),
    and averaging requires converting that to magnitude, the first way is
    likely to need less computation.

    Jerry
    --
    Engineering is the art of making what you want from things you can get.
    ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯
     
  12. (fulan) wrote in message news:<>...
    > 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


    I'd recommend you have a look at Analog Devices' Microconverter family
    of products.

    From the website (www.analog.com/microconverter):

    --------
    MicroConverter products combine analog precision and digital
    processing on a single chip.

    ADC: 12-bit SAR at up to 1MSPS
    or 24-bit sigma-delta
    up to 16 input channels

    DAC: 12-bit 5µs rail-to-rail output
    up to four separate DAC outputs

    MCU: ARM7TDMI at up to 45MIPS
    or 8052 at up to 20MIPS
    with up to 62kB Flash
    --------

    The price for a development board based on 8052 is just US$75!!!
    Schematics and Gerbers are provided, too.

    Nice, isn't it?

    JaaC
     
  13. Phil Martel

    Phil Martel Guest

    "Jaime Andres Aranguren Cardona" <> wrote in message
    news:...
    > (fulan) wrote in message

    news:<>...
    > > 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

    >

    The TI MSP430 family of microprocessors has quite a few members with A/Ds
    http://focus.ti.com/lit/ml/slab034g/slab034g.pdf

    Best wishes,
    --Phil Martel

    > I'd recommend you have a look at Analog Devices' Microconverter family
    > of products.
    >
    > From the website (www.analog.com/microconverter):
    >
    > --------
    > MicroConverter products combine analog precision and digital
    > processing on a single chip.
    >
    > ADC: 12-bit SAR at up to 1MSPS
    > or 24-bit sigma-delta
    > up to 16 input channels
    >
    > DAC: 12-bit 5µs rail-to-rail output
    > up to four separate DAC outputs
    >
    > MCU: ARM7TDMI at up to 45MIPS
    > or 8052 at up to 20MIPS
    > with up to 62kB Flash
    > --------
    >
    > The price for a development board based on 8052 is just US$75!!!
    > Schematics and Gerbers are provided, too.
    >
    > Nice, isn't it?
    >
    > JaaC
     
  14. George

    George Guest

    "Phil Martel" <> wrote in message news:<UcLCc.177199$Ly.42054@attbi_s01>...
    > "Jaime Andres Aranguren Cardona" <> wrote in message
    > news:...
    > > (fulan) wrote in message

    > news:<>...
    > > > 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


    This may sound silly bit I ask if you need a full FFT. Do you want to
    find the magnitudes of ALL frequencies in your range or just a few
    frequencies of interest. If it's the latter then you don't need FFT
    just synchrronus demodulation and that's alot simpler.

    I can point you int that direction if it would help.

    George
     
  15. fulan

    fulan Guest

    Thanx for the reply George,

    You are correct, the customer does not necessarily need a Full FFT, I
    would be interested in finding out about synchronous demodulation.

    Moussa.

    P.S.: we will still give him the ability to perform a Full FFT,however
    it should be interesting to finding out how that can be optmized.


    (George) wrote in message news:<>...
    > "Phil Martel" <> wrote in message news:<UcLCc.177199$Ly.42054@attbi_s01>...
    > > "Jaime Andres Aranguren Cardona" <> wrote in message
    > > news:...
    > > > (fulan) wrote in message

    > news:<>...
    > > > > 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

    >
    > This may sound silly bit I ask if you need a full FFT. Do you want to
    > find the magnitudes of ALL frequencies in your range or just a few
    > frequencies of interest. If it's the latter then you don't need FFT
    > just synchrronus demodulation and that's alot simpler.
    >
    > I can point you int that direction if it would help.
    >
    > George
     
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