SDMMC is a generic driver written in embedded C which provides the physical layer communication between a device and an MMC or SD card. Being generic, it can easily be made to work with any device.

Please note that this driver does not include a filesystem. However, SDMMC can be used by a filesystem service to act as the physical layer between the card and the device.

To make use of the SDMMC driver, it is first required to define your own functions to read and write to the card (e.g. sdcard_read() and sdcard_write()), as well as a function to activate and deactivate the appropriate Slave Select (SS) line (required for SPI) (e.g. sdcard_set_ss()).

struct sdmmc_dev sdcard =
{
	.read = sdcard_read,
	.set_ss = sdcard_set_ss,
	.write = sdcard_write
};

The card can then be initialised by calling the following function:

status = SDMMC_Initialise(&sdcard);

• SDXC cards are not supported (yet)
• Only single block read/write functionalities are available