libusb-1.0 - libusb データ転送

Question

Hii USBドライブからデータを読み取るコードを作成する必要があります.USBドライブは、ペンドライブであり、後でデータ取得カードになります。すべてのUSB接続を検出し、情報を出力するコードをこれだけ書きました。さらに先に進む方法はわかりませんが。また、ペンドライブからデータを読み取ることについて、いくつかのファイルを開くときのように混乱していますか？デバイスのエンドポイントを見つける方法も教えてください。現在、ヒット n トライアルを使用して見つけています。助けてください。同期および非同期 I/O に関するドキュメント全体を読みました。

enter code here    

  #include <stdlib.h>
  #include <stdio.h>
  #include <string.h>
  #include <libusb-1.0/libusb.h>

 //=========================================================================
 // This program detects usb and print out their details
 //=========================================================================

  int main (int argc, char *argv)
   {
libusb_device                    **devList = NULL;
libusb_device                    *devPtr = NULL;
libusb_device_handle             *devHandle = NULL;
libusb_context                   *ctx = NULL;            //a libusb session
struct libusb_device_descriptor  devDesc;

unsigned char              strDesc[256];
ssize_t                    numUsbDevs = 0;      // pre-initialized scalars
ssize_t                    idx = 0;
 int                        retVal = 0;

//========================================================================
// test out the libusb functions
//========================================================================

 printf ("*************************\n USB Detection             Program:\n*************************\n");
 retVal = libusb_init (&ctx);

 if(retVal < 0) {
    printf ("%d",retVal," Init Error "); //there was an error
        return 1;
          }

  //========================================================================
 // Get the list of USB devices visible to the system.
 //========================================================================

   numUsbDevs = libusb_get_device_list (ctx, &devList);

//========================================================================
// Loop through the list, looking for the device 
//========================================================================

 while (idx < numUsbDevs)
  {
  printf ("\n\n[%d]\n", idx+1);

  //=====================================================================
  // Get next device pointer out of the list, use it to open the device.
  //=====================================================================

  devPtr = devList[idx];

  retVal = libusb_open (devPtr, &devHandle);
  if (retVal != LIBUSB_SUCCESS)
     break;

  //=====================================================================
  // Get the device descriptor for this device.
  //=====================================================================

  retVal = libusb_get_device_descriptor (devPtr, &devDesc);
  if (retVal != LIBUSB_SUCCESS)
     break;

  //=====================================================================
  // Get the string associated with iManufacturer index.
  //=====================================================================

  printf ("iManufacturer = %d", devDesc.iManufacturer);
  if (devDesc.iManufacturer > 0)
  {
     retVal = libusb_get_string_descriptor_ascii
              (devHandle, devDesc.iManufacturer, strDesc, 256);
     if (retVal < 0)
        break;

     printf ("     string = %s",  strDesc);
  }

  //========================================================================
  // Get string associated with iProduct index.
  //========================================================================

  printf ("  \niProduct      = %d", devDesc.iProduct);
  if (devDesc.iProduct > 0)
  {
     retVal = libusb_get_string_descriptor_ascii
              (devHandle, devDesc.iProduct, strDesc, 256);
     if (retVal < 0)
        break;

     printf ("     string = %s", strDesc);
  }

  //==================================================================
  // Get string associated with iSerialNumber index.
  //==================================================================

  printf ("  \niSerialNumber = %d", devDesc.iSerialNumber);
  if (devDesc.iSerialNumber > 0)
  {
     retVal = libusb_get_string_descriptor_ascii
              (devHandle, devDesc.iSerialNumber, strDesc, 256);
     if (retVal < 0)
        break;

     printf ("     string = %s", strDesc);
  }

  //==================================================================
  // Print product id and Vendor id
  //==================================================================

    printf ("  \nProductid     = %d", devDesc.idProduct);
    printf ("  \nVendorid      = %d", devDesc.idVendor);

  //========================================================================
  // Close and try next one.
  //========================================================================

  libusb_close (devHandle);
  devHandle = NULL;
  idx++;

  //========================================================================
  // Selection of device by user
  //========================================================================

     if(idx==numUsbDevs) 
            { printf("\n\nselect the device :  ");
              scanf("%d",&idx);
         if(idx > numUsbDevs)
             {printf("Invalid input, Quitting.............");
              break; }    

       devPtr = devList[idx-1];

       retVal = libusb_open (devPtr, &devHandle);
           if (retVal != LIBUSB_SUCCESS)
           break;

      retVal = libusb_get_device_descriptor (devPtr, &devDesc);
           if (retVal != LIBUSB_SUCCESS)
           break;
               printf ("  \nProductid     = %d", devDesc.idProduct);
               printf ("  \nVendorid      = %d", devDesc.idVendor);

         unsigned char data[4] ; //data to read

         //data[0]='a';data[1]='b';data[2]='c';data[3]='d'; //some dummy values

          int r; //for return values 
          r = libusb_claim_interface(devHandle, 1); //claim interface 0 (the first) of   device

      if(r < 0) {

    printf("\nCannot Claim Interface");

    return 1;
                }

    printf("\nClaimed Interface");

   int actual_length; //used to find out how many bytes were written


 r = libusb_bulk_transfer(devHandle,LIBUSB_ENDPOINT_IN, data, 2, &actual_length, 0);

      if (r == 0 && actual_length == sizeof(data)) {

              // results of the transaction can now be found in the data buffer
             // parse them here and report button press
          } 
      else {
             error();
           } 


 r = libusb_release_interface(devHandle, 1); //release the claimed interface

   if(r!=0) {

            printf("\nCannot Release Interface");

            return 1;
           }

    printf("\nReleased Interface");


            idx=numUsbDevs +2;
            }

   }  // end of while loop

   if (devHandle != NULL)
   {
  //========================================================================
  // Close device if left open due to break out of loop on error.
  //========================================================================

  libusb_close (devHandle);
 }   


   libusb_exit (ctx); //close the session

   printf ("\n*************************\n        Done\n*************************\n");
   return 0;
   }

//==========================================
// EOF
//====================