Hello all,
Currently I am working on creating an HID device User Application using QT4. I am using QTCreator 1.2 on Windows Vista (32bit) Business. Here is the rundown...

Firstly, I open a file and create a buffer filled with x bytes of data from the file, then I call writefile on the buffer with the number of bytes passed as a DWORD (code below). Since the HID device has a packet size of 64 bytes, the internal USB engine parses out the data in 64 byte blocks to the device. (WORKS)
Next, once the writefile() completes, it returns to the caller and if the file was not completely read, it grabs the next set of x bytes and repeats. (WORKS SOMETIMES)

If I set the x bytes to something <=256, the transfers work exactly as described above. Once I exceed 256, the QT App crashes during the WriteFile() call. I have qDebug statements running to see when it gets to certain areas of theprogram, and I see it enter the WriteFile() but never returns before it crashes. The device however gets the complete transmission of x bytes even though the crash happens long before the device would get all the data. i.e. If I set the x bytes to 1024, the device sees all 1024 passed bytes, even though the app crashed on the WriteFile() call. My total file size right now is ~ 2048 bytes. (This could grow to < 8kB). So I set the x bytes = 4096, and fixed the descriptors in the device, also under my control, to take in 4k report size. I can break in the device code and see that it receives the entire file, but the QT App still crashes almost immediately after the writefile() has been called.

If anyone can offer some assistance it would be greatly appreciated... If I need to submit more/less code, just say the word!
Thanks to all,
AlphaWolfXV

Here is the calling code snippet:
Qt Code: 
  1. void USBProgrammer::cmdProgNew()
  2. {
  3.     unsigned int patSz = 4096;
  4.     unsigned char outputBuffer[patSz+1];
  5.     unsigned char* pOutBuf;
  6.     BYTE n;
  7.     gblHold = "";
  8.     //  teBottom->clear();
  9.     totalECHCount = 0;        //clear before we start
  10.     for(unsigned int i = 0; i < (patSz + 1); i++)
  11.         outputBuffer[i] = 0;
  12.     //we need to get what file we will be programming from the user. (if there is not one already
  13.     //selected)
  14.     if(!(lblProgramFile->text().contains(".ech")))
  15.         //we do not have  avalid file selected, lets get one...
  16.         cmdBrowse();
  17.     if (!(blnAlreadyActive))
  18.         Activate(); //need this running first...
  19.     if (!(blnAlreadyActive))
  20.     {
  21.         //this kicks us out if the board still isn't connected after
  22.         //trying again to activate!
  23.         sbarStatus->showMessage(msgProgError, 2000);
  24.         return;
  25.     }
  26.  
  27.     lblProgress->setText(progBarDownload);
  28.     pbarProgress->reset();    //put the progress bar back to 0
  29.  
  30.     //now we need to stuff the output buffer.
  31.     QFile fIn(lblProgramFile->text()), fOut();
  32.     QDataStream dsIn(&fIn); //data stream input from file.
  34.     unsigned int totCode, progBarVal;
  35.  
  36.     unsigned char tmp[0], tmp2[0],block,outCount = 2, tmpi, i;
  37.     if(!fIn.open(QIODevice::ReadOnly))
  38.     {
  39.         m.setText("Error opening ECH File!");
  40.         m.exec();
  41.         fIn.close(); return;
  42.     }
  43.     totCode = fIn.size();
  44.  
  45.     unsigned int z, q;
  46.     pOutBuf = outputBuffer;
  47.     *pOutBuf++ = 0;//first byte always 0;
  48.     *pOutBuf++ = 1;  //Code Byte, first byte received at SiLabs
  49.     while (!fIn.atEnd())
  50.     {
  51.         if (pOutBuf == outputBuffer)
  52.         {
  53.             *pOutBuf++ = 0;
  54.             q = dsIn.readRawData((char*)pOutBuf,(patSz));
  55.         }
  56.         else
  57.            q = dsIn.readRawData((char*)pOutBuf,(patSz - 1 ));
  58.         qDebug()<< "BytesWritten:"<<q;
  60.         for (unsigned int m1 = 0; m1 < (patSz+1); m1++)
  61.             s.append(QString::number(outputBuffer[m1],16) + ", ");
  62.         qDebug()<<s;
  63.         //send it out
  64.         n = hidDevice.setReport_Interrupt(outputBuffer, (patSz+1));
  65.         qDebug()<<"Return Code from Interrupt Send:" << n;
  66.         //ok, clear the buffer for the next round
  67.         for(unsigned int m1 = 0; m1 < (patSz+1); m1++)
  68.             outputBuffer[m1] = 0;
  69.         pOutBuf = outputBuffer;
  70.     }
  71. }
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And the actual WriteFile() Call:
Qt Code: 
  1. BYTE HIDDevice::setReport_Interrupt(BYTE* buffer, DWORD bufferSize)
  2. {
  3.   BYTE status = HID_DEVICE_SUCCESS;
  4.   if(bufferSize <= (DWORD)(m_OutputReportBufferLength))
  5.   {
  6.     if(isOpened())
  7.     {
  8.       DWORD bytesWritten = 0;
  9.       OVERLAPPED o = {0};
  10.       o.hEvent = CreateEvent(NULL, FALSE, FALSE, NULL);
  11.       bool a = flushBuffers();
  12.       qDebug()<< "Output Buffer Length="<<QString::number(m_OutputReportBufferLength, 10);
  13.       //try to write to the file...
  14.       if(!::WriteFile(m_Handle, buffer, bufferSize, &bytesWritten, &o))
  15.       {
  16.         qDebug()<< "Errored Out!";
  17.         //if write fails see if due to IO pending...
  18.         if(GetLastError() == ERROR_IO_PENDING) //winerror.h
  19.         {
  20.           // if there is still data to be written, wait on the event
  21.           // for m_SetReportTimeout
  22.           DWORD waitStatus = WaitForSingleObject(o.hEvent, m_SetReportTimeout);
  23.           // if the object is signaled, get the overlapped result...
  24.           // the write succeeded...
  25.           if(waitStatus == WAIT_OBJECT_0)
  26.           {
  27.             GetOverlappedResult(m_Handle, &o, &bytesWritten, FALSE);
  28.           }
  29.           else if (waitStatus == WAIT_TIMEOUT)
  30.           {
  31.             status = HID_DEVICE_TRANSFER_TIMEOUT;
  32.             CancelIo(m_Handle);
  33.           }
  34.           else
  35.           {
  36.             status = HID_DEVICE_TRANSFER_FAILED;
  37.             CancelIo(m_Handle);
  38.           }
  39.         }
  40.         else
  41.           status = HID_DEVICE_TRANSFER_FAILED;
  42.  
  43.       }
  44.       qDebug()<<"Bytes Written:"<<bytesWritten;
  45.       CloseHandle(o.hEvent);
  46.     }
  47.     else
  48.       status = HID_DEVICE_NOT_OPENED;
  49.   }
  50.   else
  51.     status = HID_DEVICE_INVALID_BUFFER_SIZE;
  52.   return status;
  53. }
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