// The next parameter identifies the type of the endpoint. Available
 // options are _BULK, _INT, _ISO, and _CTRL. When _ISO option is used,
 // addition options can be ORed to _ISO. Example:
 // _ISO|_AD|_FE
 // This describes the endpoint as an isochronous pipe with adaptive
 // and feedback attributes. See usbdefs_std_dsc.h and the USB
 // specification for details.

	//#define USE_SELF_POWER_SENSE_IO
	//#define USE_USB_BUS_SENSE_IO

    // attempt an asynchronous read operation
    bResult = WriteFile(handle,pData,dwLen,&nBytesWritten,&gOverlapped);
 
    if(!bResult)
    {
        // deal with the error code
        switch (GetLastError())
        {
            case ERROR_IO_PENDING:
            {
                // asynchronous i/o is still in progress
                switch(WaitForSingleObject(gOverlapped.hEvent, dwMilliseconds))
                {
			...
			...
			...

//dwMilliseconds
//    - Specifies the time-out interval, in milliseconds. The function
//      returns if the interval elapses, even if the operation is
//      incomplete. If dwMilliseconds is zero, the function tests the
//      data pipe and returns immediately. If dwMilliseconds is INFINITE,
//      the function's time-out interval never elapses.
//
//      Note: To use MPUSBReadInt(), the format of pEP has to be
//            "\\MCHP_EPz_ASYNC". This option is only available for
//            an IN interrupt endpoint. A data pipe opened with the
//            "_ASYNC" keyword would buffer the data at the interval
//            specified in the endpoint descriptor upto the maximum of
//            100 data sets. Any data received after the driver buffer
//            is full will be ignored.
//            The user application should call MPUSBReadInt() often
//            enough so that the maximum limit of 100 is never reached.

procedure TFormTerminale.btnWrite255PacketClick(Sender: TObject);
var 
   SendBuf: TByteBuffer;   // array di 64 byte 
   Selection: DWORD;       // double word 
   SentDataLength: DWORD;  // double word 
   I: Integer; 
begin 
   Selection := 0; 
   myOutPipe := MPUSBOpen(Selection, vid_pid, out_pipe, MP_WRITE, 0);
   if (myOutPipe = INVALID_HANDLE_VALUE) then 
   begin 
      ShowMessage('Open out data pipe Fallito'); 
Exit; // esce dalla procedura 
end; 
 
SendBuf[0] := WRITE_255; // Comando da inviare al PIC 
for I := 0 to 255 do 
begin // istruzione for da 256 cicli 
   SendBuf[1] := I; // Dato da inviare al PIC 
   if MPUSBWrite(myOutPipe, @SendBuf, 2, @SentDataLength, 1000) <> 0 then 
   begin 
      if (SentDataLength <> 2) then 
          ShowMessage('Comando WRITE_255, Fallito'); 
   end 
   else 
      CheckInvalidHandle(); 
   end; 
ShowMessage('Comando WRITE_255, completato con successo'); 
MPUSBClose(myOutPipe); 
myOutPipe := INVALID_HANDLE_VALUE; 
end;