Are there any boards with external SRAM/SDRAM available ?

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ale500
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Are there any boards with external SRAM/SDRAM available ?

Postby ale500 » Fri Sep 17, 2010 10:31 am

Hei guys/gals

The title sums it up... before I make another board has anyone done something with an external memory and has some extra boards to sell/gift/xchange ?

thanks !
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Postby Heater » Fri Sep 17, 2010 1:13 pm

I'd like to know as well,

I have a byte code interpreter for code code compiled with GNU C that could do with a few megabytes of space in external for code and data.

I guess you know that already Ale500:)
ale500
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Postby ale500 » Fri Sep 17, 2010 1:35 pm

Hei Heater, how are you doing ?... do you mean... ZOG ? :D

I'm afraid there is nothing available :(. I have a XC-1 and an external SDRAM could be used. It clogs most free pins, though. I'll have to make a board so I was thinking of either making a SDRAM-only board, or going for a new full-blown PCB with a L1 (qfp128 because the 64 has not enough pins to comfortably control external SDRAM) or G2. The problem is not to design a PCB the thing is to get a cost-effective board made...

I still think we need a simil XC-1 but with most pins in headers and not "unconnected" ;(
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Berni
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Postby Berni » Fri Sep 17, 2010 1:38 pm

The XDK kit has some SRAM on it but yeah it costs 1000 bucks.
ale500
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Postby ale500 » Fri Sep 17, 2010 2:52 pm

The XDK is nice but too expensive.
Heater
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Postby Heater » Fri Sep 17, 2010 5:33 pm

ale500,

Fine, in between all this forum hoping I've actually managed to get some work done today:)

Not Zog exactly but it runs the same byte codes. I have a ZPU bytecode interpreter written in C. It's pretty compact and will fit in an xcore with lot's of room to spare. All it needs is said external RAM and we could be running megabytes of GNU C compiled code at quite a lick in one thread of an xcore. Quite where that code comes from is another matter but and SD card seems to fit the bill. Then we could have a half decent operating system on the xcore as well.

So my dream xcore module is:
A 1 or preferably 2 core XMOS chip ( 2 core in case we start running out of internal RAM in one)
Some megabytes of external RAM.
Optionally A micro SD card.
The minimum of whatever it takes to get the XMOS chip running.
All free pins out on a DIP format for easy playing with.
MUST have a LED, all boards should have one LED.

Now I can design simple PCBs with Eagle and such but I think this is a bit beyond me what with the surface mount, high speed, switch mode regulators etc.
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Berni
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Postby Berni » Fri Sep 17, 2010 6:49 pm

Actually its not that hard to draw such a board your self. There is nothing going at really high speeds and switch mode converter chips aren't that hard to get to run as they only need a few components. Also soldering such a board is quite doable at home if you ever worked on SMDs. Problem are the bigger chips that are BGA or close to BGA (Those L2 ones) as you need some very good tools to get those on.

Id say certainly give such a board a shot.(Xmos should have made it a long time ago anyway)
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Postby ale500 » Fri Sep 17, 2010 7:23 pm

Heater:

I also got some work done today... and not only at the FTICR :).
I routed a simple Shield to get a SDRAM connected to the XC-1. You also got one of those, didn't you ?

A board is not difficult to route or do (remember my pPropFPGA ?... I do not know where I put it !). I'm just unsure if two L1s or one G2/G4 should be used (BGA144). I can get away with a pair of L1s and getting one board for some 15 Euro (4 boards in total).

I think also that all unused IOs should be available in headers.

Btw, a board without LEDs... is no fun ;-)

Berni is also right some SMT is not that difficult.. the QFN package OTOH may be very difficult.
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bsmithyman
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Postby bsmithyman » Fri Sep 17, 2010 11:09 pm

It's not on the order of megabytes, but for just a bit more moderately fast RAM, you could try the Microchip 23K256. That's 32 kB (256 kb) of RAM for each extra pin used, if you share the SPI bus with the boot flash. For simple embedded cases where you just need a little bit of scratch space, it saves implementing a parallel interface. I haven't used them yet though.

There are also some quick non-volatile RAM chips out there (e.g. Ramtron's F-RAM line) that run on a 40 MHz SPI and have immediate writes. They're quite a bit more expensive than the 23K256's sub $2 price though.
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Postby leon_heller » Fri Sep 17, 2010 11:49 pm

The Winbond W25X40VB serial flash chip that XMOS has suggested as a replacement for the difficult to obtain Atmel AT25 part is blindingly fast with a max. SPI clock of 104 MHz and a dual speed mode giving an effective clock rate of up to 208 MHz!

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