Using NOR Flash on FMC as USB Mass Storage on STM32H753

[Murali_chikkanna]

Hello,

I’m working on a project using the STM32H753 controller, and I have a NOR Flash connected via the FMC interface (BANK1 at address 0x60000000).

My goal is to use this NOR Flash memory as a USB Mass Storage Device. I’ve attempted the following approaches:

Tried formatting the NOR Flash directly from the host PC — this was unsuccessful.

Used FATFS to format the NOR Flash and then connected it to the host PC. The PC detects the filesystem and displays the correct disk size, but I’m unable to create any files on the disk from the host.

I’ve searched through the ST forums but couldn’t find any discussions related to using FMC-connected external memories as USB Mass Storage.

My questions are:

Is it possible to use external memory connected via FMC (like NOR Flash) as a USB Mass Storage device?

Can a host PC reliably access and write to memories connected to FMC through USB?

Are there any examples or reference projects demonstrating this functionality?

Any guidance or suggestions would be highly appreciated.

Thank you!

[FBL]

Hi @Murali_chikkanna 

AFAIK, it is possible to use external memory connected via FMC as a USB Mass Storage device. Unfortunately, no examples are provided.

Maybe, I can help you with connecting OSPI peripheral instead of FMC to access external NOR flash memory starting with the following example. Do you prefer using FMC interface?

[Tesla DeLorean]

I've done it with QSPI NOR FLASH

You have to use a suitable Erase Block Size, for the memory I used the minimum size was 4KB and that was reported as the sector size by the "READ CAPACITY" command or mode-page.

Apt to be VERY SLOW, better to use eMMC (chip down version of the MicroSD card via SDIO/SDMMC interface)

[Murali_chikkanna]

Thank you for your response.

Yes, I am using the FMC interface as required. On my custom hardware, the NOR Flash is connected to FMC Bank1, so I have no alternative interface available.

The NOR Flash device in use is MT28EW128ABA1LPC-0SIT from Micron. I have modified the usbd_storage_if.c file to support this NOR Flash. As a result, the device is detected correctly as a Mass Storage Device with the appropriate size.

However, when I attempt to format the NOR Flash from the host computer, the sector read and write operations are triggered, but the formatting process ultimately fails.

I enabled debug logs to capture the SCSI commands during the formatting attempt — please refer to the attached logs for more details.

If needed, I can share the relevant portions of the code as well. I would greatly appreciate your guidance in resolving this issue.

Thanks & Regards,
Murali Chikkanna