MMC card with spi-sd-card.c

[Sebastian Huber]

Gene Smith wrote:
> I have been trying to use an MMC with the "spi/sd" drivers in RTEMS. I 
> worked until it tries to send two commands in a loop waiting for idle 
> conditon in an init routine:
> 
> rv = sd_card_send_command( e, SD_CARD_CMD_APP_CMD, 0);
> CLEANUP_RVSC( rv, sc, sd_card_driver_init_cleanup, "Send: 
> SD_CARD_CMD_APP_CMD");
> rv = sd_card_send_command( e, SD_CARD_ACMD_SD_SEND_OP_COND, 0);
> CLEANUP_RVSC( rv, sc, sd_card_driver_init_cleanup, "Send: 
> SD_CARD_ACMD_SD_SEND_OP_COND");

These commands set the SD Card into SPI mode.

> 
> The first on seems to work but the 2nd on fails.
> 
> I found something in a Samsung MMC manual that says when waiting for 
> idle on it you should do this instead.
> 
> rv = sd_card_send_command( e, SD_CARD_CMD_SEND_OP_COND, 0);
> CLEANUP_RVSC( rv, sc, sd_card_driver_init_cleanup, "Send: 
> SD_CARD_CMD_SEND_OP_COND");
> 
> When I do this instead the code detects idle after two loops (stepping 
> with debugger) and continues on with no apparent errors and registers 
> the card.
> 
> I am not sure if there are other ways a MMC differs from a SD.

In MMC mode CRC is enabled by default and the state machine is different.  CRC
is currently not supported in the SD Card driver.

> 
> -gene
> 
> 
> 
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-- 
Sebastian Huber, Embedded Brains GmbH

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