What if I need to store file larger than 4GB?

[HKPhysicist]

Hello Friends,
I am watching this library for my next portable storage project:
https://github.com/stm32duino/STM32SD
My target board is NUCLEO-H533RE

I plan to develop it as the MCU for portable storage. So how to tune the library to allow file large than 4GB?

I want a MCU which can transfer up to 208MB/s over the SDIO bus.

Yours faithfully,
Hope every one in France will return home and office soon. Best Wishes.

[alleyxd]

The 4 GB limit is FAT32's per-file limit, not the library's. Format the card as exFAT and you can go past it. SDXC cards (64 GB and up) come formatted exFAT anyway.

STM32SD is built on FatFs, and the current default config (src/ffconf_default_80286.h) already has FF_FS_EXFAT 1 with LFN enabled, so it should work as is. If your setup picks an older config, drop an ffconf_custom.h in your sketch folder with FF_FS_EXFAT 1 and FF_USE_LFN >= 1 (the README describes the override). FF_LBA64 is only needed for volumes over 2 TB.

On speed: 208 MHz is the SDR104 clock, but over a 4-bit bus that gives 104 MB/s max, not 208 MB/s. It also needs the card switched to 1.8 V signalling, so check what the board supports. In practice FatFs overhead and card write speed will be the limit well before that.

[HKPhysicist]

Thanks for the information.