Getting started with FAT Filesystem on SD/MMC cards over SPI

[Robert S. Grimes]

Thanks Sebastian,  I'll give it a try.  Likely I won't have anything to 
report on until next week.

One question in clarification: you said "it must be possible to drive 
the clock with inactive chip select".  Do you mean the clock must always 
be running, or that there needs to be a way to drive the clock sometimes 
while the socket is _not_ selected?  Maybe it'll become obvious when I 
delve into the code, but I was just a bit curious...

Thanks again, and say "Hello" to Thomas for me,
-Bob


Sebastian Huber wrote:
> Hi,
> I wrote a SD Card driver that uses the LibI2C interface.  It is already
> included in the RTEMS CVS under the LibChip:
>
> c/src/libchip/i2c/spi-sd-card.h
> c/src/libchip/i2c/spi-sd-card.c
>
> It works with the SPI drivers for the MPC5566EVB and MPC8313ERDB boards.
>   I had problems to initialize some SD Cards (1 out of 10), but this is
> maybe a problem of the SPI interface in these cards.  The initialization
> sequence is not perfect and may need improvement.  One problem is that
> not all documents are publicly available.
>
> The SD Card driver registers itself to LibBlock so you can use easily
> imfs and dosfs.
>
> Example code:
>
> c/src/lib/libbsp/powerpc/mpc55xxevb/startup/sd-card-init.c
>
> The crucial point for the SPI driver is that it must be possible to
> drive the clock with inactive chip select:
>
> [...]
> /* Stop */
> sc = sd_card_stop( e);
> CHECK_SC( sc, "Stop");
>
> /* Start with inactive chip select */
> sc = rtems_libi2c_send_start( e->minor);
> CHECK_SC( sc, "Send start");
>
> /* Set transfer mode */
> rv = rtems_libi2c_ioctl( e->minor, RTEMS_LIBI2C_IOCTL_SET_TFRMODE,
> &e->transfer_mode);
> CLEANUP_RVSC( rv, sc, sd_card_driver_init_cleanup, "Set transfer mode");
>
> /* Send idle tokens with inactive chip select */
> rv = sd_card_query( e, e->response, SD_CARD_COMMAND_SIZE);
> CLEANUP_RVSC( rv, sc, sd_card_driver_init_cleanup, "Inactive chip select
> delay");
>
> /* Activate chip select */
> sc = rtems_libi2c_send_addr( e->minor, 1);
> CLEANUP_SC( sc, sd_card_driver_init_cleanup, "Send address");
> [...]
>
> So you have to activate the chip select in rtems_libi2c_send_addr() and
> not before.
>
> It would be nice if you could use this code.
>
> Gene Smith wrote:
>   
>> What you are talking about here my h/w does and it is something I need
>> to do too. However, at this point I don't have a clue how. So a "HowTo"
>> would be most appreciated and I could contribute what I learn.
>>
>> All I have worked with is the IMFS in a simple way.
>>
>> -gene
>>
>> Robert S. Grimes wrote:
>>     
>>> Hello,
>>>
>>> My hardware provides support for SD/MMC flash cards over SPI, so now I
>>> need to implement suitable drivers for this.  Because it would need to
>>> be read by Windows machines, and because it is sufficient for my
>>> application, it seems the dosfs is the way to go.
>>>
>>> I've got a low level SPI driver for my BSP (powerpc/virtex under RTEMS
>>> 4.8), and I've written some chip drivers on top of that, so I'm
>>> comfortable with the SPI level.
>>>
>>> But where do I go from here?
>>>
>>>    1. How do I "include" the dosfs in my application?  Is it a matter of
>>>       #define CONFIGURE_ macros, and if so, which?  (As an aside, is
>>>       there one central place where all these macros are defined?  If
>>>       so, I haven't found it...)
>>>    2. How do I get dosfs to work via the SPI bus?  What must my driver
>>>       look like?
>>>
>>> Any pointers or roadmap well appreciated - TIA
>>> -Bob
>>>
>>> P.S. Sounds like a request for a "HowTo" on my part - I'd be happy to
>>> write one for the Wiki...
>>>       
>> _______________________________________________
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>> http://rtems.rtems.org/mailman/listinfo/rtems-users
>>     
>
>
> --
> Sebastian Huber, Embedded Brains GmbH
>
> Address : Obere Lagerstr. 30, D-82178 Puchheim, Germany
> Phone   : +49 89 18 90 80 79-6
> Fax     : +49 89 18 90 80 79-9
> E-Mail  : sebastian.huber at embedded-brains.de
> PGP     : Public key available on request
>
> Diese Nachricht ist keine geschäftliche Mitteilung im Sinne des EHUG.
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