[Libusb-win32-devel] USB transfers are sometimes lost

[Kjell E. A. <kje...@ta...>]

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After having used libusb-win32 exstensively for more than a year I have
come across a problem with usb_bulk_read().

After several hours of errorfree communication, an usb bulk read package
is lost (it shows on a SW bus analyzer).

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A bulk endpoint is continously read like this :

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while ( ! TerminateThread )

{

      i =3D usb_bulk_read( pDevH, 0x82, buffer, 64, 1000 );   // 1 sec
timeout

      if ( i > 0 )

            process the data

      else if ( i !=3D TIMEOUT )

            process error

}

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Q1 : Can anybody confirm that using the libusb API in this way may
result in lost packages ?

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The plan now is to try using the async API with 2 buffers (ping-pong)
like shown below and check if the problem disappears :

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i =3D 0;

i +=3D usb_bulk_setup_async( pDevH, &context1, 0x82 );

i +=3D usb_bulk_setup_async( pDevH, &context2, 0x82 );

i +=3D usb_submit_async( context1, ibuf1, 64 );

i +=3D usb_submit_async( context2, ibuf2, 64 );

if ( i !=3D 0 )

      printf( "\nErrors : %d", i ); // Close down, replug etc. ??

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while ( ! TerminateThread )               =20

      {

      //--- Buffer 1 ---

      i =3D usb_reap_async( context1, INFINITE ); // INIFINITE =3D -1

      if ( i < 0 )

            printf( "\nReap 1 error : %d", i );

      else

            {

            printf( "\nReap 1 received : %d, %c", i, ibuf1[0] );

            process data

}

      i =3D 0;  =20

      //i +=3D usb_free_async( &context1 );

//i +=3D usb_bulk_setup_async( pDevH, &context1, 0x82 );

      i +=3D usb_submit_async( context1, ibuf1, 64 );

      if ( i !=3D 0 )

            printf( "\nErrors : %d", i ); // Close down, replug etc. ??

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      //--- Buffer 2 ---

      i =3D usb_reap_async( context2, INFINITE );

      if ( i < 0 )

            printf( "\nReap 2 error : %d", i );

      else

{

            printf( "\nReap 2 received : %d, %c", i, ibuf2[0] );

            process data

}

      i =3D 0;  =20

      //i +=3D usb_free_async( &context2 );

//i +=3D usb_bulk_setup_async( pDevH, &context2, 0x82 );

i +=3D usb_submit_async( context2, ibuf2, 64 );

      if ( i !=3D 0 )

            printf( "\nErrors : %d", i ); // Close down, replug etc. ??

      }

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i  =3D usb_cancel_async( context1 );

i +=3D usb_cancel_async( context2 );

i +=3D usb_free_async( &context1 );

i +=3D usb_free_async( &context2 );

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Q2 : Is this the correct way to use the async API ?

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Q3 : Am I right in assuming that the usb_free_async() and
usb_bulk_setup_async() which is commented out inside the loop is really
unneccessary ? (it seems to work with a small limited testprogram)

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Any response on my three questions would be greatly appreciated !

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Best regards,

Kjell Eirik