usb通讯时readfile没有响应。
上位机和单片机使用标准usb协议通讯，上位机的相关代码：

C# code

//这里的详细代码没有给出。openDevice();openHandles();//重点：        int result = FileIOApiDeclarations.WriteFile(this._WriteHandle,ref command[0], command.Length,ref TxdBytes, 0);                if (result == 0)                {                    int error = Usb.DebuggingDeclarations.GetLastError();                    string str = "";                    long size = 0;                    Usb.DebuggingDeclarations.FormatMessage(Usb.DebuggingDeclarations.FORMAT_MESSAGE_ALLOCATE_BUFFER | Usb.DebuggingDeclarations.FORMAT_MESSAGE_FROM_SYSTEM | Usb.DebuggingDeclarations.FORMAT_MESSAGE_IGNORE_INSERTS, ref size, error, 0, str, 0, 0);                    Log.WriteLog("error when set read command" + str);                    this.closeHandles();                    return retResult;                }                //FileIOApiDeclarations.CloseHandle(this._WriteHandle);                int relReaded = 0;                Usb.FileIOApiDeclarations.OVERLAPPED overlapped = new Usb.FileIOApiDeclarations.OVERLAPPED();                this.PrepareForOverlappedTransfer(ref overlapped);                System.Threading.Thread.Sleep(500);                result = FileIOApiDeclarations.ReadFile(this._ReadHandle, ref data[0], length, ref relReaded, ref overlapped);                /*[color=#FF0000]错误出现在此处，每次到这里程序完全没有响应了，拔掉USB设备时程序下行，GetLastError会返回31                 前边的获取GUID，writeFlie都是正确的  [/color]*/                if (result == 0) // error handle                {                    int error = Usb.DebuggingDeclarations.GetLastError();                    if (error == FileIOApiDeclarations.ERROR_IO_PENDING)                    {                        FileIOApiDeclarations.WaitForSingleObject(overlapped.hEvent, 30000);                        int readBytes = 0;                        result = FileIOApiDeclarations.GetOverlappedResult(this._ReadHandle, ref overlapped, ref readBytes, false);                        if (result != 0)                            retResult = true;                    }

C/C++ code

      init_USBused();      init_TimerA();         init_TimerB();         RWsw = P2IN & BIT5;        // for USB Write Data         if(RWsw == 0)        {            FCTL2 = FWKEY + FSSEL0 + FN0;            FlashErase(ipatient);            FlashErase(isetup);        }          MCU_D12RST_0;                             //片选usb      _NOP();      MCU_D12RST_1;                             //reset usb 芯片      bEPPflags.value = 0;      _EINT();      reconnect_USB();      P1IE = 0X04;      opcode = 0xff;      index = 0;          while(1)      {          if (bEPPflags.bits.ep2_rxdone)              //端点2接收响应          {            bEPPflags.bits.ep2_rxdone = 0;            //flag set zero            if(opcode == 0xff)            {              //D12_ReadEndpoint(4, 6, EpBuf);              if(EpBuf[0] == 0x01)//if(EpBuf[0] == 0x01)              {                opcode = 1;                addr = EpBuf[2]*0x100 + EpBuf[3];                length = EpBuf[4]*0x100 + EpBuf[5];                cur_addr = addr;                fileoff = 0;              }              else if(EpBuf[0] == 0x00)              {                opcode = 0;                addr = EpBuf[2]*0x100 + EpBuf[3];                length = EpBuf[4]*0x100 + EpBuf[5];                cur_addr = addr;                fileoff = 0;              }             }            else if(opcode == 1)                            //将usb接到的数据写入寄存器                      {              if(index == 256)               {                index = 0;                for(ptr = 0; ptr < 256; ptr++,cur_addr++)                  FlashWB(cur_addr,data[ptr]);                fileoff += 256;                if(fileoff == length)                {                  opcode = 0xff;                  fileoff = 0;                  index = 0;                }              }            }          }//if bEPPflags.bits.ep2_rxdone          if(opcode == 0)                            //read operation          {              if(rindex == 0)              {                for(ptr = 0; ptr < 256; ptr++,cur_addr++)                  data[ptr] = *(char *)(cur_addr);              }              _DINT();              D12_WriteEndpoint(5,64,&data[rindex]);    //通过point5传输数据              _EINT();                rindex = (rindex + 64) % 256;              fileoff += 64;              //D12_WriteEndpoint(5,64,&data[index]);              //index = (index + 64) % 256;              if(fileoff == length)              {                  opcode = 0xff;                  fileoff = 0;                  rindex = 0;                  index = 0;                  icount = 0;              }            }           if (bEPPflags.bits.timer)            {                               //计时器中断响应              bEPPflags.bits.timer = 0;            }           if (bEPPflags.bits.bus_reset)          {                                 //总线重起中断响应            _DINT();            bEPPflags.bits.bus_reset = 0;            _EINT();                                  } // if bus reset          if (bEPPflags.bits.suspend)          {                               //挂起中断响应            _DINT();            bEPPflags.bits.suspend= 0;            _EINT();            if((P4OUT & D12_SUSPD) == D12_SUSPD)            {              D12_SUSPD_0;              P5DIR = 0XFF;              P5OUT = 0xFF;              P5DIR = 0X0;              P4DIR = 0XFF;              P4OUT = 0xFF;              D12_SetDMA(0xC3);              D12_SUSPD_1;            }          } // if suspend change          if (bEPPflags.bits.setup_packet)          {                               //接收到设置包中断处理            _DINT();            bEPPflags.bits.setup_packet = 0;            control_handler();            _EINT();                              //P1OUT |=D12SUSPD;          } // if setup_packet        } // Main Loop