STM32G0B1RET6 USB Host – How to Get USB Flash Drive Total and Free Storage Using FatFs?

[Berlin-raj123]

Hello STM32 Community,

I am currently working on a USB Flash Drive interface using STM32G0B1RET6 with USB Host and FatFs.

The USB Flash Drive is working correctly. When I plug in a USB Pendrive, my STM32 can detect it, mount the filesystem, and successfully create/write files to the Pendrive.

Now I would like to display/check the following information:

1. Total USB Flash Drive storage
2. Used storage
3. Free/available storage
4. Detect whether the USB is almost full

My current code is:

static void USBH_UserProcess(USBH_HandleTypeDef *phost, uint8_t id)
{
    switch (id)
    {
        case HOST_USER_CLASS_ACTIVE:

            Appli_state = APPLICATION_READY;

            USB_Detect_flag = 1;   // USB is plugged

            Mount_USB();

            HAL_GPIO_WritePin(GPIOC, LED_RED_Pin, GPIO_PIN_RESET);

            /* Check USB free space */
            if (usb_space_result == FR_OK)
            {
                displayText16x16_DMA(20, 190,
                                     "USB HAS SPACE",
                                     GREEN_COLOR,
                                     BLACK_COLOR);
            }
            else
            {
                /* USB does not have enough free space
                   OR filesystem access failed. */

                displayText16x16_DMA(50, 200,
                                     "USB SPACE ERROR",
                                     RED_COLOR,
                                     BLACK_COLOR);
            }

            break;
    }
}

My storage-checking function is:

FRESULT Check_USB_FreeSpace(void)
{
    FATFS *fs;
    DWORD free_clusters;
    uint64_t free_bytes;
    FRESULT res;

    res = f_getfree("/", &free_clusters, &fs);

    if (res != FR_OK)
    {
        printf("f_getfree ERROR = %d\r\n", res);
        return res;
    }

    free_bytes = (uint64_t)free_clusters *
                 (uint64_t)fs->csize *
                 512ULL;

    printf("Free Clusters = %lu\r\n", free_clusters);
    printf("Cluster Size  = %u\r\n", fs->csize);
    printf("Free Bytes    = %llu\r\n", free_bytes);
    printf("Free KB       = %llu\r\n", free_bytes / 1024ULL);

    /*
     * Minimum free space required
     * 10 KB
     */
    if (free_bytes < (10ULL * 1024ULL))
    {
        printf("USB FULL / LOW SPACE\r\n");
        return FR_DENIED;
    }

    printf("USB HAS SPACE\r\n");

    return FR_OK;
}

My question

Is this the correct way to calculate the USB Flash Drive storage?

I would like to get something like:

USB Total Storage : 14.9 GB
USB Used Storage  : 3.2 GB
USB Free Storage  : 11.7 GB

or, for example:

Total : 8 GB
Used  : 2.5 GB
Free  : 5.5 GB