Cannot R/W some 32GB USB drives or bigger from STM32F469NI

Hello, I have built a small app following the USB Host Mass Storage example from Keil. I am using STM32F469I-Discovery and the app just transfer all files stored in SD card to any USB device that is connected to the USB port. It works fine, reaching a rate of about 870KBps which I think is not bad for the full speed I have set. The problem is that I have made all the testing with a 32GB USB flash drive, however when try with a different 32GB USB device or a 64GB I get  usbDeviceError meaning that the device appears to be disconnected. All other device capacities under 32GB work perfect.

Can anybody please point me in the right direction on where the problem might be ? I am using USB Host + FatFS + RTOS2 - RX5 with CMSIS. No additional libraries are been used in case it is relevant for finding the problem.

Thank you guys in advance for your help

  • Hi Migmel,

    first you should check which format your flash drive is formatted with.

    I suspect FatFS supports FAT32 and it is very likely that flash drives with capacity more than 32 GB are formatted to exFAT or even NTFS which will not work with FatFS.

    You can reformat them on a PC or even embedded system to FAT32 and see if that works.

    Best regards, Milorad

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