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ARM7 with external memory

Discussion in 'Embedded' started by Henrik [6650], May 2, 2006.

  1. Hello group,

    I have been tasked with investigating possible solutions for a new product.
    I have normally used micros with flash/ram memory onboard, but now we need
    to have atleast 1MB codememory and the same amount of RAM, so I have been
    looking for a while to find some possible setup. It appears to me that
    singlechip MCU's are much more popular (naturally), but I would like to ask
    all of you for an advice on the following:

    What micros do you use with external memory? Why?
    What RTOS? Why?

    Total systemcost is an issue for this product.

    Thanking you in advance for any input on the matter.
     
    Henrik [6650], May 2, 2006
    #1
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  2. Henrik [6650]

    Chris Hills Guest

    Is this home work?
     
    Chris Hills, May 2, 2006
    #2
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  3. You cannot make any decision based on just requirement for memory size.
    You need to know processing requirements and peripherals.

    If large Flash/RAM is the only requirement, then AT91M40800 is a good low
    cost alternative.
    Many would consider the AT91RM9200 running Linux as a good candidate.
    --
    Best Regards,
    Ulf Samuelsson

    This message is intended to be my own personal view and it
    may or may not be shared by my employer Atmel Nordic AB
     
    Ulf Samuelsson, May 2, 2006
    #3
  4. Of course not, I am aware of that, and perhaps I should have been more
    detailed in my previous post. However, my peripheral requirements is likely
    to be fulfilled by most devices. I only need a serial port and a SPI and a
    few IO. Of course I need 16 bit timers and preferably a dedicated PIT for
    the RTOS.
    My reason for requesting large flash/ram sizes is that I need to do quite a
    lot of dataprocessing and storing. I plan on using SQLite and use SPI flash
    for storage. For the GUI I plan to maintain rather large amounts of
    dataobjects in RAM for easy and fast access. Hence the high RAM demand.
    Also, since the customers specs as to datamanipulation is not yet 100%
    defined, I prefer to start out large, and shrink if possible.

    Actually I have been looking at AT91 series since we use atmel in almost
    every product we ship today, but I feared that those would "soon" be EOL
    (with nothing than a "gut feeling" to base it on) and I need to be able to
    manufacture this product for atleast 5 years from january 2007. I hope I am
    totally mistaking here??

    With AT91 in mind, could anybody suggest a RTOS to look at?

    Thank you,

    Henrik
     
    Henrik [6650], May 2, 2006
    #4
  5. Absolutely not.
    This is for our next generation controllers for animalfeeding. Our current
    solution is based on a 8051 architecture, but due to the amount of data we
    need to process and store, we want to "climb the ladder" a step or two.

    Thank you,

    Henrik
     
    Henrik [6650], May 2, 2006
    #5
  6. Henrik [6650]

    Richard Guest

    Total systemcost is an issue for this product.

    What is your target unit cost and estimated volume? Maybe COTS hardware
    would provide a simple solution if your interfaces are that simple (as per
    other post).

    Regards,
    Richard.

    http://www.FreeRTOS.org
    *Now for ARM CORTEX M3!*
     
    Richard, May 2, 2006
    #6
  7. AT91M42800A will do the job for you then. This is 0,35u.

    If this makes you nervous, and you can wait just a little,
    then the AT91SAM9260 and AT91SAM7SE
    should be arriving this summer.
    The AT91RM9200 is avaialble, but will be more expensive.

    --
    Best Regards,
    Ulf Samuelsson

    This message is intended to be my own personal view and it
    may or may not be shared by my employer Atmel Nordic AB
     
    Ulf Samuelsson, May 2, 2006
    #7
  8. I believe that we would be able to do the hardware for about 150USD which is
    what we have as an initial budget. We have been looking at COTS hardware,
    but we have not been able to find any that match our needs and demands. We
    bare temperature extremes below -15 degrees celcius and the environment i
    relative noisy (electrically, that is).
    Our estimated annual volume is about 2-2.5K units.

    Thank you,
    Henrik
     
    Henrik [6650], May 2, 2006
    #8
  9. I'd use only a small flash for booting, enough RAM for code+data, and an
    SD/MMC card for code and permanent data. All SD/MMC cards have an SPI mode,
    and firmware updates and database backups will be very easy then.
    If you need speed you could always use the sd cards' 4 bit mode.


    Mit freundlichen Grüßen

    Frank-Christian Krügel
     
    Frank-Christian Kruegel, May 2, 2006
    #9
  10. Check out www.mechatronicbrick.dk or www.iotech.dk.

    The IO Technologies pricing for
    AT91RM9200 CPU module + 8 MB of dataflash + 16 MB of SDRAM is 68 Euros = $85

    --
    Best Regards,
    Ulf Samuelsson

    This message is intended to be my own personal view and it
    may or may not be shared by my employer Atmel Nordic AB
     
    Ulf Samuelsson, May 2, 2006
    #10
  11. Henrik [6650]

    CBFalconer Guest

    Nobody has any idea what you are trying to do. I think you are
    approaching things from the wrong end. What does the system do;
    what are its inputs; its outputs; its time frames, etc. What, if
    any, human interface is needed. What, if any, cow (or other
    beastly) interface is needed. You would be well advised to write
    the code and then look for something on which to execute the
    result. 150 USD can buy a lot of processing power these days. A
    noisy environment probably means such things as shielding, ecc
    memory, self-healing software, and various fail-safes.

    --
    "If you want to post a followup via groups.google.com, don't use
    the broken "Reply" link at the bottom of the article. Click on
    "show options" at the top of the article, then click on the
    "Reply" at the bottom of the article headers." - Keith Thompson
    More details at: <http://cfaj.freeshell.org/google/>
    Also see <http://www.safalra.com/special/googlegroupsreply/>
     
    CBFalconer, May 2, 2006
    #11
  12. I am not sure I understand you on how I attack this from the wrong end. My
    questions is about what possible platforms I could use, with respect to
    external memory and a possible RTOS. Of course I would not recklessly jump
    at the first answer without further investigation and close collaboration
    with my HW colleagues. I just need a starting point, because my primary
    field of work so far has been singlechip MCU's.
    Our peripheral demands are quite few as per my previous post and the human
    interface is as simple as a small characterbased LCD. The primary human
    interface is via serial link from a PC.
    various fail-safes.

    Yes, it means exacly that. Things that we have been doing for over 10 years
    and that have proven their worth in thousands of units shipped across the
    world.

    Thank you,
    Henrik
     
    Henrik [6650], May 3, 2006
    #12
  13. If your human interface is a "small characterbased LCD", why do you
    need an external memory ARM ? - flash ARM singe chip uC reach up towards
    1Mbyte.

    Off chip memory devices have a lot more bus/antenna to crash in noisy
    environments !

    Actual Code size is not likely to be an issue, so I'd look at serial
    data flash devices - they will easily store anything you might want to
    display on a character LCD, as well as hold your data sets ?
    In data flash devices, Atmel have 66MHz Models, and Winbond have just
    released 150MHz models, which is faster than any ARM7 can pump the
    data.... [ and way faster than any human can read the LCD :) ]
    These things are tiny - use more than one, if it simplifies partition
    of GUI ( eg Language ? ) and data sets ( removable ? )

    If the ARM you choose has limited SPI's, add a small CPLD to handle
    card/spi MUX.

    -jg
     
    Jim Granville, May 3, 2006
    #13
  14. If you read carefully, he is asking for 1 MB of SRAM as well.

    --
    Best Regards,
    Ulf Samuelsson

    This message is intended to be my own personal view and it
    may or may not be shared by my employer Atmel Nordic AB
     
    Ulf Samuelsson, May 3, 2006
    #14
  15. Well, sort of; first he says

    "For the GUI I plan to maintain rather large amounts of
    dataobjects in RAM for easy and fast access. Hence the high RAM demand."

    but then, he says

    "the human interface is as simple as a small characterbased LCD. The
    primary human interface is via serial link from a PC."

    so I focused more on what the unit has to DO, than on what resource the
    first guess plucked from the air :)

    Using 1MB of SRAM to drive a CharLCD is a serious missplacement of resource.

    -jg
     
    Jim Granville, May 3, 2006
    #15
  16. resource.

    The unit operates in cycles, where when a cycle is performed, a lot of
    (several 100's) of dataobjects need to be read and modified over and over
    again until the cycle completes. Modifications can occur via the serial link
    or as a result of the cycle progress, requring me to have two sets of
    dataobjects and track changes from both sides. Therefore my plan is to load
    all of these objects into an objectstore in RAM upon cyclestart and then
    persist these objects when the cycle ends.

    The estimated ressourcedemands is in no way "plucked from the air", of
    course we do not want to shoot way over the top, but also we do not want to
    be limited by some parts internal memory halfway through the project or
    redesign some essential part of the software, because we are tight on
    memory.

    The model we use, we have implemented with great success on Windows CE.NET
    for our larger Controller Unit, so the design is proven and we want to stick
    with it where it makes sense.

    When I started this thread, my inital goal was for people to comment on what
    microcontroller units they would use with external memory and why, same
    thoughts on the RTOS. I am fairly new to this group, although fairly "old"
    in the world of embedded SW engineering, and I apologize for not having been
    more specific about the product and my motivation for using external memory.
    I feel I have come off here as an amateur, which was not intended.
     
    Henrik [6650], May 3, 2006
    #16
  17. That's new information, but even adding this, it does not sound like 1MB
    of SRAM... what size are these objects ?
    You could look at these new devices :

    http://www10.edacafe.com/nbc/articles/view_article.php?section=ICNews&articleid=266197

    http://www.st.com/stonline/stappl/press/news/year2006/p2022.htm

    they have 96K SRAM, 512KF, plus Ethernet/USB/CAN in the top model, with
    dual-bus memories, burst FLASH, and claim 96MHz...

    They also have numerous external BUS options, so you could connect more
    memory.

    USB sounds like it could be very usefull.

    -jg
     
    Jim Granville, May 3, 2006
    #17
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