Cport 详细解释和应用

转载：http://www.cnblogs.com/Bung/archive/2011/05/20/2051636.html

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;

if (FirstByte = $FE) and (SecondByte = $7F) then

Ready := True;

if Ready and (count>=84) then

begin

。。。。

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,

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;
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;

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;

if (FirstByte = $FE) and (SecondByte = $7F) then

Ready := True;

if Ready and (count>=84) then

begin

。。。。

end;

procedure TCustomComPort.CreateHandle;

begin

FHandle := CreateFile(

PChar('\\.\' + FPort),

GENERIC_READ or GENERIC_WRITE,

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;

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Cport 详细解释和应用

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