Supported ICs

Introduction

SD Host provides a hardware communication interface to access SD cards, MMC cards, and SDIO cards, implementing data storage and device expansion features.

Characteristics of SD Host are as follows:

  • Protocol support: Supports SD, MMC, and SDIO protocols, offering high compatibility.

  • Data width: Supports both 1-bit and 4-bit data bus width, accommodating different transmission rate requirements.

  • High-speed operation: Supports both default mode and high-speed mode, with data transfer clock up to 50MHz.

  • Block transfer: Supports both single block and multiple block transfers, making best of bus bandwidth.

  • DMA support: Realizes data transfer automatically with an internal DMA controller, reducing CPU load.

  • SDIO expansion: Supports access to SDIO devices, e.g. wireless communication modules and Bluetooth modules, enhancing system functionality.

Note

  • Communication with SDIO cards is currently not supported in RTL8730E.

  • If you need to use RTL8721F for communication with SDIO cards, please contact Realtek.

Application

SD Host provides basic support for Virtual File System (VFS) application and USB Mass Storage Class (MSC) application.

VFS

VFS provides a convenient interface for interacting with multiple underlying file systems, facilitating multi-platform development.

The hierarchical architecture and main related drivers of VFS application based on SD Host are shown in the figure:

../../../_images/vfs_fatfs_sdh.svg

VFS Architecture Based on SD Host

Users can refer to VFS on SD card to learn how VFS performs file-level operations on SD cards or MMC cards based on SD Host.

Note

Memory capacity of SD cards or MMC cards supported in VFS is up to 32GByte.

USB MSC

Devices plugged into the SD Host slot by USB MSC, e.g. SD cards, are treated as an USB storage devices, which enhances the flexibility of data management.

For more details, please refer to Mass Storage Device Solution.

Troubleshooting

File System Init Fail

Phenomenon

Message “File System Init Fail” appears while running the VFS example.

Cause

  • The SD card or MMC card is not formatted.

  • The key sector contents of the formatted SD card or MMC card have been corrupted.

Solution

  • It is recommended to format the SD card or MMC card based on a standard file system.

  • Choose an appropriate format supported by FATFS, e.g. FAT32.

Note

Backup your important data before formatting for it will erase all the data on the cards.