小菜求教关于串口通信

Question

请教大哥们，在串口通信中的整个详细过程。请尽量详细点。什么缓冲区啊之类的

Answer 1

unit U_APISerialPort;interfaceuses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls, ExtCtrls;
const
  Wm_CommNotify = WM_User +12;
type
  Tfrm_SerialPort = class(TForm)
    pnl1: TPanel;
    lbl_SerialPort: TLabel;
    cbb_SerialPort: TComboBox;
    btn_OpenSerialPort: TButton;
    btn_CloseSerialPort: TButton;
    pnl2: TPanel;
    lbl_RevData: TLabel;
    mem_RevData: TMemo;
    pnl3: TPanel;
    lbl_SendData: TLabel;
    mem_SendData: TMemo;
    pnl4: TPanel;
    btn_Send: TButton;
    btn_Close: TButton;
    btn_SaveToFile: TButton;
    procedure FormShow(Sender: TObject);
    procedure btn_OpenSerialPortClick(Sender: TObject);
    procedure btn_CloseSerialPortClick(Sender: TObject);
    procedure btn_CloseClick(Sender: TObject);
    procedure btn_SendClick(Sender: TObject);
    procedure FormDestroy(Sender: TObject);
    procedure FormCreate(Sender: TObject);
    procedure btn_SaveToFileClick(Sender: TObject);
  private
    procedure CommInitialize;
    procedure MsgComm(var Msg:TMessage);Message Wm_CommNotify;
    function WriteStr(const Str:string):Boolean;
    { Private declarations }
  public
    { Public declarations }
  end;
  TComm=class(TThread)
  protected
    procedure Execute;override;
  end;var
  frm_SerialPort: Tfrm_SerialPort;
  g_Hcom,g_Post_Event:THandle;
  g_LpolW,g_LpolR:POverlapped;
  g_RXComm:TComm;
  g_bFlag :Boolean;implementation{$R *.dfm}
procedure TComm.Execute;
var
  l_dwEvtmask,l_dwOvres,l_dwbb:DWORD;
  l_bRXFinish:BOOL;
begin
  while True do
  begin
    l_dwEvtmask := 0;
    l_bRXFinish := WaitCommEvent(g_Hcom,l_dwEvtmask,g_LpolR);//等待串口事件EV_RXCHAR
    if not l_bRXFinish then
      if GetLastError()= ERROR_IO_PENDING then//正在接受数据;
      begin
        l_dwbb:=WaitForSingleObject(g_LpolR^.hEvent,500);//等待500MS
        case l_dwbb of
          WAIT_OBJECT_0: l_bRXFinish:=GetOverlappedResult(g_Hcom,g_LpolR^,l_dwOvres,False);
          WAIT_TIMEOUT: l_bRXFinish:= False//定是益出
        else
          l_bRXFinish := False;
        end;
      end
    else
      l_bRXFinish:=False;
     if l_bRXFinish then
     begin
       ResetEvent(g_Post_Event); //同步事件复位
       PostMessage(frm_SerialPort.Handle,Wm_CommNotify,0,0);
     end;
  end;
end;procedure Tfrm_SerialPort.FormShow(Sender: TObject);
begin
  try
    btn_CloseSerialPort.Enabled := False;
    cbb_SerialPort.Clear;
    mem_RevData.Clear;
    mem_SendData.Clear;
    cbb_SerialPort.AddItem('',nil);
    cbb_SerialPort.AddItem('COM1',nil);
    cbb_SerialPort.AddItem('COM2',nil);
    cbb_SerialPort.AddItem('COM3',nil);
    cbb_SerialPort.AddItem('COM4',nil);
  except on e:Exception do
    ShowMessage(e.Message);
  end;
end;procedure Tfrm_SerialPort.btn_OpenSerialPortClick(Sender: TObject);
begin
  if cbb_SerialPort.Text ='' then
  begin
    MessageDlg('请选择COM口',mtWarning,[mbOK],0);
  end
  else
  begin
    btn_CloseSerialPort.Enabled := True;
    try
      CommInitialize;
    except on e:Exception do
        ShowMessage(e.Message);
    end;
  end;
end;procedure Tfrm_SerialPort.btn_CloseSerialPortClick(Sender: TObject);
begin
  btn_CloseSerialPort.Enabled := False;
end;procedure Tfrm_SerialPort.btn_CloseClick(Sender: TObject);
begin
  Self.Close;
end;procedure Tfrm_SerialPort.CommInitialize;
var
  l_Lpdcb:TDCB;
begin
  g_Hcom:= CreateFile(PAnsiChar(cbb_SerialPort.Text),GENERIC_READ or GENERIC_WRITE,0,nil,
         OPEN_EXISTING,FILE_FLAG_OVERLAPPED,0);
  g_bFlag := True;
  if g_Hcom <> invalid_handle_value then
  begin
    SetupComm(g_Hcom,4096,4096);
    GetCommState(g_Hcom,l_Lpdcb);
    l_Lpdcb.BaudRate := 9600;
    l_Lpdcb.StopBits :=0;
    l_Lpdcb.ByteSize :=8;
    l_Lpdcb.Parity :=0;
    SetCommState(g_Hcom,l_Lpdcb);
    SetCommMask(g_Hcom,EV_RXCHAR);
  end
  else
    ShowMessage('无法打开串口');
end;
function Tfrm_SerialPort.WriteStr(const Str: string): Boolean;
var
  l_DwCharsWritten,l_DwRes:DWORD;
  l_S_DATA:string;
  l_BRes:Boolean;
begin
  l_BRes :=False;
  l_S_DATA:=Str;
  if g_Hcom<>invalid_handle_value then
  begin
    l_DwCharsWritten :=0;
    l_BRes :=WriteFile(g_Hcom,PChar(l_S_DATA)^,Length(l_S_DATA),l_DwCharsWritten,g_LpolW);
    if not l_BRes then
    begin
      if GetLastError()=ERROR_IO_PENDING then
      begin
        l_DwRes :=WaitForSingleObject(g_LpolW^.hEvent,INFINITE);
        if l_DwRes=WAIT_OBJECT_0 then
          l_BRes :=GetOverlappedResult(g_Hcom,g_LpolW^,l_DwCharsWritten,False)
        else
          l_BRes:=True;
      end;
    end;
  end
  else
  Result := l_BRes;
end;procedure Tfrm_SerialPort.MsgComm(var Msg: TMessage);
var
  l_bclear:Boolean;
  l_coms :TComStat;
  l_dwcbNum,l_dwCbread,l_dwlpErrors:DWORD;
  l_s:string;
begin
  l_bclear :=ClearCommError(g_Hcom,l_dwlpErrors,@l_coms);
  if l_bclear then
  begin
    l_dwcbNum :=l_coms.cbInQue;//获取接受缓冲区待接收字节数
    SetLength(l_s,l_dwcbNum+1);//分配内存
    ReadFile(g_Hcom,PChar(l_s)^,l_dwcbNum,l_dwCbread,g_LpolR);//读串口
    SetLength(l_s,l_dwCbread);//分配
    SetEvent(g_Post_Event);//同步事件置位
    mem_RevData.Lines.Add(l_s);
  end;  
end;procedure Tfrm_SerialPort.btn_SendClick(Sender: TObject);
var
  l_S_DATA:string;
begin
  l_S_DATA :=mem_SendData.Text;
  if  WriteStr(l_S_DATA) then
     ShowMessage('无法发送数据')
  else
     ShowMessage('发送成功');
end;procedure Tfrm_SerialPort.FormDestroy(Sender: TObject);
begin
  CloseHandle(g_LpolW^.hEvent);
  CloseHandle(g_LpolR^.hEvent);
  Dispose(g_LpolR);
  Dispose(g_LpolW);
  g_LpolW :=nil;
  g_LpolR :=nil;
  g_RXComm.Terminate;
  SetEvent(g_Post_Event);
  CloseHandle(g_Post_Event);
  CloseHandle(g_Hcom);
end;procedure Tfrm_SerialPort.FormCreate(Sender: TObject);
begin
//  CommInitialize;
  New(g_LpolW);
  New(g_LpolR);
  g_LpolW^.Internal :=0;
  g_LpolW^.InternalHigh :=0;
  g_LpolW^.Offset :=0;
  g_LpolW^.OffsetHigh :=0;
  g_LpolW^.hEvent :=CreateEvent(nil,True,False,nil);
  g_LpolR^.Internal :=0;
  g_LpolR^.InternalHigh :=0;
  g_LpolR^.Offset :=0;
  g_LpolR^.OffsetHigh :=0;
  g_LpolR^.hEvent :=CreateEvent(nil,True,False,nil);
  PurgeComm(g_Hcom,PURGE_TXABORT or PURGE_RXABORT or PURGE_TXCLEAR or PURGE_RXCLEAR);
  g_Post_Event:=CreateEvent(nil,True,True,nil);
  g_RXComm :=TComm.Create(False);
end;procedure Tfrm_SerialPort.btn_SaveToFileClick(Sender: TObject);
begin
  try
    if mem_RevData.Text =''then
      ShowMessage('接收数据不能为空!')
    else
      mem_RevData.Lines.SaveToFile('d:\receive.tex');
  except  end;  
end;end.

Answer 2

下载spcomm组件，自己看源代码

Answer 3

1楼的，是网上流行的一个经典写法。串口实际上也有很多写法，不过，实际上也就是几个API，弄懂机制就会变得简单。
http://www.moon-soft.com/program/bbs/readelite515510.htm