Cport 应用集合

通过comport获取计算机中的所有串口号：

procedure TForm1.FormCreate(Sender: TObject);  //获取计算机中的串口号
var
  Cnumber:TStrings;
  i:Integer;
begin
  cbb2.Items.Clear;
  Cnumber:=TStringList.Create;
  EnumComPorts(Cnumber);  //获取串口号函数：EnumComPorts
  for i:=0 to Cnumber.Count-1 do
  begin
  cbb2.Items.Add(Cnumber.Strings[i])
  end;
  cbb2.ItemIndex:=0;
  Cnumber.Free;
end;

procedure TForm1.btn7Click(Sender: TObject);  //打开串口
begin
  ComPort1.Port:=cbb2.Text;
  if ComPort1.Connected then
  begin
    ComPort1.Close;
    ComPort1.Open;
  end
  else
  ComPort1.Open;
end;

我开始用comport时发现它每次14个字符触发一次接收事件，而我要接收的一帧完整数据是82个字符，因此我在每帧的前后个加了开始码和结束码，共84个字符，当Count值大于84我才处理，程序片断如下：

procedure TFCOMM.ComPortRxChar(Sender: TObject; Count: Integer);
var
  ReceiveData:TDateRec;
  p:Pbyte;
  Block : array[0..85] of Char;
begin
  if (not Ready)  then
    begin
      ComPort.Read(p,1);   //开始码为$7FFE,接收时先收的是$FE
      move(p, SecondByte,1);
      if SecondByte = $FE then        //如果收到的字节是$FE，那就看看下一个是不是$7F
        begin
          FirstByte := SecondByte;
          ComPort.Read(p,1);;
          move(p, SecondByte,1);
        end;
    end;

  if (FirstByte = $FE) and (SecondByte = $7F) then
    Ready := True;

  if Ready and (count>=84) then
    begin
      。。。。
    end;
end;

Spcomm有的是定时查询的方式读COM口；而ComPort用Overlapped机制进行COM读写，只要COM有数据接收到，ComPort就能够从Event响应，并通知应用程序接收，所以，某种ComPort的实时性更好。但是，Overlapped的Event被触发，并不是COM接入一段完整的信息才触发，是Windows自己决定的，我在多个计算机和不同的Windows版本上试过，其触发后接收到的字符数并不一样。因此，需要自己建一个缓冲区来处理数据。

procedure TCustomComPort.CreateHandle;
begin
  FHandle := CreateFile(
    PChar('\\.\' + FPort),
    GENERIC_READ or GENERIC_WRITE,
    0,
    nil,
    OPEN_EXISTING,
    FILE_FLAG_OVERLAPPED,  // 以Overlapped方式打开COM口
    0);

  if FHandle = INVALID_HANDLE_VALUE then
    raise EComPort.Create(CError_OpenFailed, GetLastError);
end;

procedure TComThread.Execute;
var
  EventHandles: array[0..1] of THandle;
  Overlapped: TOverlapped;
  Signaled, BytesTrans, Mask: DWORD;
begin
  FillChar(Overlapped, SizeOf(Overlapped), 0);
  Overlapped.hEvent := CreateEvent(nil, True, True, nil);
  EventHandles[0] := FStopEvent;
  EventHandles[1] := Overlapped.hEvent; // COM口上的Overlapped事件
  repeat
    // 等待COM上的事件
    // wait for event to occur on serial port
    WaitCommEvent(FComPort.Handle, Mask, @Overlapped);
    Signaled := WaitForMultipleObjects(2, @EventHandles, False, INFINITE);
    // if event occurs, dispatch it
    if (Signaled = WAIT_OBJECT_0 + 1)
      and GetOverlappedResult(FComPort.Handle, Overlapped, BytesTrans, False)
    then
    begin
      // 通知应用程序接收数据 
      FEvents := IntToEvents(Mask);
      DispatchComMsg;
    end;
  until Signaled <> (WAIT_OBJECT_0 + 1);
  // clear buffers
  SetCommMask(FComPort.Handle, 0);
  PurgeComm(FComPort.Handle, PURGE_TXCLEAR or PURGE_RXCLEAR);
  CloseHandle(Overlapped.hEvent);
  CloseHandle(FStopEvent);
end;