Not able to mount SD card with SDMMC 4-bit bus, but with 1 bit but it works fine

[Bhavin-D]

Board = NUCLEO-F756ZG

SD Card Spec = SDHC Class 10

Board to SD card connection wire length = ~10cm

SDMMCCLK clock divide factor = 8 (So SDMMC_CK = 3 MHz)

Accept CLK line, on all lines 22K pull-up resisters are connected.

I am trying to mount and read/write into an SD card with an SDMMC 4-bit bus without DMA. But the FATFS f_mount() function fails with a FR_NOT_READY error. Where the same hardware with the SDMMC 1-bit bus software, mounts an SD card and is able to read/write in an SD card.

Can you please help me to work with 4-bit SDMMC?

What could be the possible reason specific to 4-bit?

Can you please share a working example?

[KDJEM.1]

Hello @Community member​ and welcome to Community :) ;

I recommend you How do I Create a File System on a SD card using STM32CubeIDE? article. This FAQ can help you to create a file system on a SD card with 4-bit bus using STM32F746G-DISCO

I assume that you get FR_NOT_READY error because one of the following possibilities is suspected:

• No medium in the drive.
• Wrong hardware configuration.
• The storage device has broken.

When your question is answered, please close this topic by choosing Select as Best. This will help other users find that answer faster.

Kaouthar

[Amel NASRI]

Hi @Community member​ ,

Is your project generated with STM32CubeMX?

If yes, could you please check that the workaround provided in this discussion https://community.st.com/s/question/0D53W0000216T7oSAE/mxsdiosdinit-wrong-bus-wide-initialization is applied.

Please let me know the result (in both cases: problem resolved or not).

-Amel