ARM7 with external memory

"Henrik [6650]" wrote:
> "Richard" <nospam@thanks.com> wrote in message
>
>>> 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.
> 
> 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.

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.  

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"CBFalconer" <cbfalconer@yahoo.com> wrote in message
news:4457966E.78163900@yahoo.com...

> 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.

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.

>A noisy environment probably means such things as shielding [...] and
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] wrote:
> 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.

  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 wrote:
> Henrik [6650] wrote:
...
>
>   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.
>
If you read carefully, he is asking for 1 MB of SRAM as well.

-- 
Best Regards,
Ulf Samuelsson
ulf@a-t-m-e-l.com
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 wrote:
> Jim Granville wrote:
> 
>>Henrik [6650] wrote:
> 
> ...
> 
>>  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.
>>
> 
> If you read carefully, he is asking for 1 MB of SRAM as well.

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" <no.spam@designtools.co.nz> wrote in message
news:4458830c$1@clear.net.nz...
> 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.

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] wrote:
> "Jim Granville" <no.spam@designtools.co.nz> wrote in message
> news:4458830c$1@clear.net.nz...
> 
>>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.
> 
> 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.

That's new information, but even adding this, it does not sound like 1MB 
of SRAM... what size are these objects ?

> 
> 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.

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