Lpc2000

darcy_will wrote:
> Hi all,
> 
> Please excuse my ignorance of these issues.  I'm only just looking 
> to begin playing with an Olimex LPC2148 dev kit having finally got 
> the thing up and running with GCC/Insight etc...
> 
> Because the development board comes with an MMC (and SD?) slot I 
> just assumed this is probably the type of flash device I'd end up 
> using in our "product" (just a home project at the moment).  Having 
> had a bit of a look around it's fairly easy to see that SD has 
> overtaken MMC as far as price and availability go.  This certainly 
> makes me think that SD is the flash type to go with.
> 
> If a FAT16/32 file system is implemented on this kit (using 
> something like RDCF or EFSL for example), how easy is it to swap the 
> flash cards between MMC and SD?  I've seen that SD and MMC can both 
> use the same transfer protocol to the uC, but does the change in 
> format also require an overhaul of the flash driver on the uC?
>
> This is kind of a dual purpose question...  
> a) Can the same driver used for MMC cards be used for SD?
> b) if not, how different is the interface?

In an SD card product manual that I have, it is mentioned that
MMC cards should not be clocked faster than 400 kHz during
initialisation.

Also I've seen it mentioned in example code that MMC cards
first need at least 80 clocks without being selected during
startup. Not sure if this is MMC specific though.

So, yes, you should be able to use the same driver (a SPI mode
driver), provided that you do the 400 kHz thing (and possibly
also the 80 clocks).

Physically, an SD card is thicker than a MMC card, so an
MMC card will fit in a SD slot, but not the other way around.

> I'm not looking to be able to use both types of flash cards on the 
> same project...  more curious as which is the one to go with.

I would go for SD card, it's more modern and also cheaper.

> There certainly *seem* to be more examples out there for MMC than 
> SD...  In fact I haven't found any examples of SD file systems on 
> the LPC21xx range.  Maybe I'm just not looking hard enough?  :)

As far as I know, the official SD/MMC specification is not public,
that probably explains a lot.

> Any help would be greatly appreciated!

Regards,
Bertrik