Question
SDMMC FATFS
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 :

