Result := -1;
      break;
    end;

    for i:=1 to iReadNum do                                                     //字節讀取到后串口緩沖自動清空
    begin
      RetStr := RetStr + buffer[i];                                             //將讀取到的字節添加到讀到字節緩沖區
    end;
    iTotalNum := iTotalNum + iReadNum;

    if iTotalNum >= NumberOfBytesToRead then                                    //如果讀取到的字節數大于等于需要讀取數返回
    begin
      TotalBytes := iTotalNum;
      Break;
    end;

    crTimer := GetTickCount;
    if ((crTimer - dwTimer) > Timeout) or ((crTimer < dwTimer) and
        (crTimer+(4294967295-dwTimer) > Timeout)) then                          //超時返回
    begin
      TotalBytes := iTotalNum;
      Result:=-2;
      Break;
    end;
  end;
end;

///////////////////////////////////
//發送指定字節數的數據到串口
//返回:  0表示成功,
//      -1表示錯誤,
//////////////////////////////////
function TSerialControl.WriteCom(var SendStr:string;                              //要發送字節緩沖區
                                 NumberofBytesToWrite:DWord;                    //要發送的字節數
                                 PurgeFlag:Boolean=FALSE;                       //是否先清緩沖區
                                 TimeOut:DWord=1000                             //超時
                                 ):Integer;
var
  i:integer;
  iWritedNum:DWord;
  buffer:array[1..500] of char;
begin
  if NumberofBytesToWrite = 0 then
  begin
    NumberofBytesToWrite := Length(SendStr);
  end;
  for i:=1 to NumberofBytesToWrite do
  begin
    //buffer[i] := Chr(StrToAsc(Copy(SendStr,i,1)));
    buffer[i] := Chr(ord(SendStr[i]));
  end;


  if PurgeFlag then
  begin
    PurgeComm(m_hComm,PURGE_TXCLEAR or PURGE_TXABORT);                          //清除數據緩沖區
  end;

  WriteFile(m_hComm,                                                            //操作句柄
            buffer,                                                             //數據緩沖區
            NumberOfBytesToWrite,                                               //要寫入的字節長度
            iWritedNum,                                                         //實際寫入的字節長度
            nil);                                                               //overlapped buffer

  if iWritedNum = NumberOfBytesToWrite then                                     //如果字節全部寫入
  begin
    Result:=0;
  end else
  begin
    Result:=-1;
  end;
end;

///////////////////////////////////
//清發送和接收緩沖區
//////////////////////////////////
procedure TSerialControl.purgeReadWrite(RWFlag:Integer);
begin
  if RWFlag=0 then
  begin
    PurgeComm(m_hComm, PURGE_RXCLEAR or PURGE_RXABORT);
  end else
  begin
    PurgeComm(m_hComm,PURGE_TXCLEAR or PURGE_TXABORT);
  end;
end;

///////////////////////////////////
//com pin 4 dtr
///////////////////////////////////
procedure TSerialControl.SetDTR(Status:Boolean);
var
  com_dcb:DCB ;
begin
  GetCommState(m_hComm, com_dcb);
  com_dcb.Flags:=Com_dcb.Flags and (not($03*DTRBit));
  if Status then
  begin
    com_dcb.Flags:=Com_dcb.Flags or (DTR_CONTROL_ENABLE*DTRBit);
  end else
  begin
    Com_Dcb.Flags:=Com_Dcb.Flags or (DTR_CONTROL_DISABLE*DTRBit);
  end;
  SetCommState(m_hcomm, com_dcb);
end;

///////////////////////////////////
//com pin 7 rts
///////////////////////////////////
procedure TSerialControl.SetRTS(Status:Boolean);
var
  com_dcb:DCB ;
begin
  GetCommState(m_hComm, com_dcb);
  com_dcb.Flags:=Com_dcb.Flags and (not($03*RTSBit));
  if Status then
  begin
    com_dcb.Flags:=Com_dcb.Flags or (RTS_CONTROL_ENABLE*RTSBit);
  end else
  begin
    Com_Dcb.Flags:=Com_Dcb.Flags or (RTS_CONTROL_DISABLE*RTSBit);
  end;
  SetCommState(m_hcomm, com_dcb);
end;

///////////////////////////////////
//
///////////////////////////////////
procedure TSerialControl.GetCtsDsr(var CTSStatus,DSRStatus:Boolean);
var
  dwStatus:DWord;
begin
  GetCommModemStatus(m_hComm,dwStatus);
  if (dwStatus and MS_CTS_ON)>0 then
  begin
    CTSStatus:=True;
  end else
  begin
    CTSStatus:=FALSE;
  end;

  if (dwStatus and MS_DSR_ON)>0 then
  begin
    DsrStatus:=True;
  end else
  begin
    DsrStatus:=FALSE;
  end;
end;

///////////////////////////////////
//
///////////////////////////////////
function TSerialControl.WaitForCTSDSR(var CTSStatus,DSRStatus:Boolean):Boolean;
var dwMask,dwStatus:DWord;
    bRet:Boolean;
begin
    SetCommMask(m_hComm,EV_CTS and EV_DSR);
    bRet:=FALSE;
    WaitCommEvent(m_hComm,dwMask,nil);
    if (dwMask and EV_CTS)<>0 then
    begin
        GetCommModemStatus(m_hComm,dwStatus);
        if (dwStatus and MS_CTS_ON)<>0 then
        begin
            CTSStatus:=True;
        end else
        begin
            CTSStatus:=FALSE;
        end;
        bRet:=True;
    end;
    if (dwMask and EV_DSR)<>0 then
    begin
        GetCommModemStatus(m_hComm,dwStatus);
        if (dwStatus and MS_CTS_ON)<>0 then
        begin
            DSRStatus:=True;
        end else
        begin
            DSRStatus:=FALSE;
        end;
        bRet:=True;
    end;
    {MS_CTS_ON CTS為ON
　　MS_DSR_ON DSR為ON
　　MS_RING_ON RING為ON
　　MS_ELSD_ON RLSD為ON}
    Result:=bRet;
end;

function StrToAsc(mstr:string):integer;                                         //返回字符的ASC值
begin
  Result := 126 - CompareStr('~',mstr);
end;

end.