[sdiy] Spartan 3 and camera memory cards

[Eric Brombaugh]

Grant,

Modern MMC, SD & SDHC flash memory cards don't necessarily require an  
OS, FAT file systems, etc. It is possible to access the raw contents  
in a linear fashion, and there are a lot of folks out there who do  
just that for FPGA interfacing. Writing raw data to them from a PC may  
require non-standard tools & techniques but is possible.

If you decide to go with standard filesystems though, there is freely  
available code to support such. Not sure that it's been ported to  
Picoblaze, but the code and documentation is there. Picoblaze may  
present a challenge due to limited code space, but I know that SD/SDHC  
FAT filesystems are available for PIC, dsPIC, ARM, AVR, etc.

I'd recommend searching through the archives of the comp.arch.fpga and  
comp.arch.embedded Usenet newsgroups - I've seen a lot of discussions  
on this topic there.

Eric

On Dec 10, 2008, at 8:23 PM, Grant Richter wrote:

> Anybody know how to access modern camera card data with a Spartan 3?
>
> The old cards were like dynamic RAM, give them a RAS and a CAS and  
> they returned the byte at the site.
>
> Modern cards have file systems, which if memory serves, requires an  
> Operating System, needing a FAT to handle sectors, bad sectors, non- 
> sequential sectors and all kinds of complications having to do with  
> a non-linear address space. My research shows all over the counter  
> flash cards with linear address spaces to be gone.
>
> A simple OS for Picoblaze would work, I just want to update large  
> data chunks of internal flash from data on a camera card. Then  
> switch to internal flash, the cards work is done.  Xilinx already  
> makes a solution for updating the FPGA it self via flash cards, but  
> not outboard data chunks. The status of that chip is also up in the  
> air. First they say they do and then they don't, and then they say  
> they will and then they won't, they're undecided now, what am I  
> gonna do? (Thanks Django).
>
> All suggestions appreciated. And for those who care, this MAY end up  
> in a commercial product with a production run of 50 units lifetime.
>
> Thank you kindly.
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