Optimierungsproblem mit Array in Subroutine

typedef unsigned char  BYTE;

...

// SDCARD

void sdcard_test (void) {

    FATFS fs[1];         /* Work area (file system object) for logical drives */

    FIL fsrc, fdst;      /* file objects */

    BYTE buffer_sd[4096];   /* file copy buffer */

    FRESULT res;         /* FatFs function common result code */

    UINT br, bw;         /* File read/write count */

    disk_initialize(0);

    /* Register work area for each volume (Always succeeds regardless of disk status) */

    f_mount(0, &fs[0]);

    /* Open source file on the drive 1 */

    res = f_open(&fsrc, "0:my_test.txt", FA_OPEN_EXISTING | FA_READ);

    sprintf(&lcd.buffer[0],"Open Read res=%d",(UINT)res); //lcd.buffer ist global definiert

    printf_tft(1,15,lcd.buffer);

    /* Create destination file on the drive 0 */

    res = f_open(&fdst, "0:dstfile1.txt", FA_CREATE_ALWAYS | FA_WRITE);

    sprintf(&lcd.buffer[0],"Open Write res=%d",(UINT)res);

    printf_tft(1,30,lcd.buffer);

    /* Copy source to destination */

    for (;;) {

        res = f_read(&fsrc, buffer_sd, sizeof(buffer_sd), &br);    /* Read a chunk of src file */

        sprintf(&lcd.buffer[0],"Read Anzahl: %d (res=%d)",br,(UINT)res);

        printf_tft(1,45,lcd.buffer);

        delay(100);

        if (res || br == 0) break; /* error or eof */

        res = f_write(&fdst, buffer_sd, br, &bw);               /* Write it to the dst file */

        if (res || bw < br) break; /* error or disk full */

    }

    /* Close open files */

    f_close(&fsrc);

    f_close(&fdst);

    /* Unregister work area prior to discard it */

    f_mount(0, NULL);

}