RE: [ECOS] memory requirements, TI OMAP 5910 (ARM 925T)?

["Doyle, Patrick" <WPD at dtccom dot com>]

Hello Jim,
I'm always glad to hear of more people using eCos on the OMAP :-).  I was
planning on using just the internal RAM for a project I am currently working
on (and may, in fact, still do that), but I ran into the solvable problem
that RedBoot really wanted to use 68-72 Kbytes of RAM buffer data going to
the flash.  In general, the flash support in RedBoot really likes to have an
entire sector's (plus some more) worth of RAM available before it writes to
a sector.  We, too, did not want to use external RAM in our design, but put
it in, just in case.  Since it was there, I went ahead and used it and put
plans for a RAM-less version on the back burner for now.

I would suggest you look at Micron's Mobile SDRRAM
(http://www.micron.com/products/category.jsp?path=/DRAM/Mobile&ct=hp.pl) if
you want reasonable density with low power.  You can place this part into a
deep sleep mode if you manage to optimize your application to use the
internal RAM on the OMAP, or you can fall back to using it, if you find that
you cannot optimize your application, or if your schedule starts to become
critical.

I presume you are aware of this, but, just in case you are not, in addition
to the 192Kbytes of RAM that are shared between the ARM and the DSP, there
is 160Kbytes of DSP-only RAM (64K DARAM and 96K SARAM, I think).  So if your
application fits into that memory, it frees up the 192K for the OMAP.  Check
out TI's "Reference Framework 1" for an example of an absolute minimal
footprint DSP application.

I read in a follow-on email that you are considering only running the
network stack when you need to and you wondered about the possibility of
initializing it on the fly.  My intuition says that won't work well
(although there are others on this list who have much greater intuition
about eCos than I).  If you want to use the network stack to load new code
on the board and/or upload/download data in an offline mode, you could
consider two applications -- your ultra-low power application that disables
the external RAM while collecting data, and your more feature filled
application that used more power.  The ultra-low power application could be
configured to run using internal RAM only.

Someday I plan on releasing a new version of OMAP support (I'm still
cleaning it up, and still awaiting the copyright assignment).  One of the
options I have considered for our application is exactly what you've
described -- an internal SRAM only version.  I'll keep you posted as things
progress.

--wpd


> -----Original Message-----
> From: Jim Partan [mailto:jpartan@whoi.edu] 
> Sent: Friday, July 18, 2003 5:43 PM
> To: ecos-discuss@sources.redhat.com
> Subject: [ECOS] memory requirements, TI OMAP 5910 (ARM 925T)?
> 
> 
> Hi,
> 
> I'm starting to evaluate the TI OMAP 5910 (ARM 925T) for a 
> new embedded 
> system. I'd like to use eCos. Right now I'm specifically trying to 
> estimate the approximate memory requirements. I'm just 
> getting the eCos
> configuration tool up and going, but if anyone has a vaguely similar
> system and can let me know what their approximate memory 
> usage is, that 
> would be great!!
> 
> I'm interested in using (on ARM 925T):
> 
> 	TCP/IP stack with embedded webserver
> 	ethernet driver (perhaps SMSC LAN91c111)
> 	flash filesystem
> 	RS232 serial port ('5910 has some integrated UARTs)
> 	an external realtime clock (probably on I2C bus)
> 	maybe a few other very small things (watchdog, etc)
> 
> 	ideally USB as well, but this is not at all critical
> 		(the '5910 has an integrated USB interface)
> 
> The OMAP 5910 has 192kbytes of internal SRAM. I'd love to avoid
> putting an external RAM chip on the board. The catch is that
> the internal SRAM is shared with a TI DSP sharing the same
> package (it's a dual-core package, ARM 925T and TI '55x DSP),
> and of course I'd like as much RAM as possible dedicated to the
> DSP side of things...
> 
> Thanks very much for any help!!
> 
> Jim
> 
> 
> 
> -- 
> Before posting, please read the FAQ: 
> http://sources.redhat.com/fom/ecos
> and search the list 
> archive: http://sources.redhat.com/ml/ecos-discuss
> 

-- 
Before posting, please read the FAQ: http://sources.redhat.com/fom/ecos
and search the list archive: http://sources.redhat.com/ml/ecos-discuss