SDIO

SDIO driver includes two layers: hardware access layer (HAL) and RT-Thread adaptation layer.
HAL provides basic APIs for accessing SDIO peripheral registers. For details, please refer to the API documentation of SDIO HAL.
The adaptation layer provides SDCARD access functionality. After initialization, it registers an SDCARD device that can be accessed by the file system.

Driver Configuration

The hardware driver is initialized by default as a block device for SDMMC cards. It can be enabled for each project using the menuconfig tool, usually saved in C header files. By default, the configuration is saved as rtconfig.h.

The following example shows the flags defined in a project header file that enables SDIO in BSP. For RT-Thread, its SDMMC device also needs to be enabled. Steps to select configuration for BSP:

  • Enter “menuconfig” in the command under the project

  • Select “RTOS —>”

  • Select “On-chip Peripheral Driver—>”

  • Select “Enable SDIO” Enable SDIO driver, define macro BSP_USING_SDIO

#define BSP_USING_SDIO

Here shows the RT-Thread SDIO driver configuration:

  • Select “RTOS”—>

  • Select “RT-Thread Components —>”

  • Select “Device Driver—>”

  • Select “Using SD/MMC device drivers”

  • Select “The stack size for mmcsd thread” Enter 2048, change macro RT_MMCSD_STACK_SIZE, 1024 is too small. Other configurations remain unchanged if not needed.

#define RT_USING_SDIO
#define RT_SDIO_STACK_SIZE 512
#define RT_SDIO_THREAD_PRIORITY 15
#define RT_MMCSD_STACK_SIZE 2048
#define RT_MMCSD_THREAD_PREORITY 22
#define RT_MMCSD_MAX_PARTITION 16

After configuration, users need to include header files in all source code that needs to access the driver.

Using SDMMC

The adapter layer registers hardware support functions requested by RT-Thread and implements these functions using HAL. For users using RT-Thread, the following code can be used as an example:

// Find and open sdcard as block device
rt_device_t dev = rt_device_find("sd0");    // get block device
rt_err_t err = rt_device_open(dev, RT_DEVICE_FLAG_RDWR);

// read sdmmc, it's a block device, read size should be block based(default as 512)
char * buf = malloc(4096);
blk = len >> 9;
int size = rt_device_read(dev, addr, (void *)buf, blk);

// Write sdmmc
size = rt_device_write(dev, addr, buf, blk);


...

// Close block device
rt_device_close(dev);