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Associate II
February 11, 2026
Question

SDMMC FATFS

  • February 11, 2026
  • 2 replies
  • 168 views

Hi ST Community,

I'm facing an issue with FatFs on SDMMC where f_open() or even f_mount() returns FR_DISK_ERR, even though the SD card is initializing correctly at the HAL level.

Here's a summary of the problem and what I’ve verified so far.

  • HAL_SD_Init() completes successfully
  • Card information is read correctly:
    • CID
    • CSD
    • RCA
    • Capacity (LogBlockNbr, LogBlockSize)
  • SDMMC interface appears operational
  • Raw HAL read/write tests (CID/CSD) work fine
I would be grateful if ST experts or anyone familiar with SDMMC + FatFs integration please help me to resolve this issue :
samuel_l_0-1770781136742.png

 

2 replies

Technical Moderator
February 11, 2026

Hello @samuel_l 

Please refer to the example FatFs_uSD_Standalone on STM32CubeH7.

 

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Andrei Chichak
Lead
February 11, 2026

I expect that the SDCard/eMMC chip is new and does not have a file system on it yet. I.E. it needs to be formatted.