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Detect SD card file system as device over USB cable using LPCXpresso5411?

Question asked by Ronan O'Driscoll on Jul 12, 2018
Latest reply on Feb 1, 2020 by Kerry Zhou

I was looking at the USB examples from the SDK of the LPCXpresso5411. Using the example "SDK_2.2.1_LPCXpresso54114/boards/lpcxpresso54114/usb_examples/usb_rom_device_msc_ram" I successfully got a PC to recognise the LPCXpresso5411 as a USB device with a USB cable using the hard coded files in ramdisk.c. eg the code below will show basic files when a usb cable is plugged into a PC.


static const struct FAT12_img
    const uint8_t *data;
    int offset;
    int size;
} FAT12_img[] = {
    /* Each sector is of size 512 Bytes i.e., 0x200 Bytes */
    {FAT12_header, 0, sizeof(FAT12_header)},                       /* FAT12 at sector 0,1 */
    {FAT12_root_dir, 0x400, sizeof(FAT12_root_dir)},               /* Root dir at sector 2 */
    {FAT12_file_readme_txt, 0x600, sizeof(FAT12_file_readme_txt)}, /* README.TXT file data */
    {FAT12_file_index_htm, 0xC00, sizeof(FAT12_file_index_htm)},   /* INDEX.HTM file data */

void DataRam_Initialize(void)
    int i;
    extern uint8_t g_memDiskArea[];
    memset(g_memDiskArea, 0, MSC_MEM_DISK_SIZE);
    for (i = 0; i < sizeof(FAT12_img) / sizeof(FAT12_img[0]); i++)
        memcpy(&g_memDiskArea[FAT12_img[i].offset], FAT12_img[i].data, FAT12_img[i].size);


However I would like to integrate this with the FatFs for an SD card. With help from this forum, I have the FatFs and SD card working. So instead of the "static struct FAT12_img" I m trying to use the FIL structure from ff.h.



typedef struct {
     _FDID     obj;               /* Object identifier (must be the 1st member to detect invalid object pointer) */
     BYTE     flag;               /* File status flags */
     BYTE     err;               /* Abort flag (error code) */
     FSIZE_t     fptr;               /* File read/write pointer (Zeroed on file open) */
     DWORD     clust;               /* Current cluster of fpter (invalid when fprt is 0) */
     DWORD     sect;               /* Sector number appearing in buf[] (0:invalid) */
     DWORD     dir_sect;          /* Sector number containing the directory entry */
     BYTE*     dir_ptr;          /* Pointer to the directory entry in the win[] */
     DWORD*     cltbl;               /* Pointer to the cluster link map table (nulled on open, set by application) */
#if !_FS_TINY
     BYTE     buf[_MAX_SS];     /* File private data read/write window */
} FIL;


Would I do something like 


FIL fil;

memcpy(&g_memDiskArea[fil.obj], fil.buff, fil[i].size);


I m not too sure how to do this, but any point in the right direction would be great.