串口异步设置

赶任务 在论坛上下载了个串口程序。
没有仔细研究，想请教下哪里是改同步和异步的标志
程序如下com.h
#pragma once
#include "afxwin.h"// CCom 对话框
class CCom : public CDialog
{
DECLARE_DYNAMIC(CCom)public:
CCom(CWnd* pParent = NULL);   // 标准构造函数
virtual ~CCom();// 对话框数据
enum { IDD = IDD_COM };protected:
virtual void DoDataExchange(CDataExchange* pDX);    // DDX/DDV 支持 DECLARE_MESSAGE_MAP()
public:
virtual BOOL OnInitDialog();
void InitComBox(void);
HANDLE OpenCOM(int iPort);
void Close();
int  Read(char* buffer, int iMaxLength);
int Write(char* buffer, int iLength); afx_msg void OnBnClickedOk();
public: BOOL m_bOpenCom;
CComboBox m_cbCom;
CComboBox m_cb_Rate;
CComboBox m_cb_Parity;
CComboBox m_cb_Data;
CComboBox m_cb_Stop; HANDLE m_hHandle;
int m_nComNo;
int m_nRate;
int m_nParity;
int m_nData;
int m_nStop;
};// Com.cpp : 实现文件
//
#include "stdafx.h"
#include "YT.h"
#include "Com.h"
#include ".\com.h"
// CCom 对话框
IMPLEMENT_DYNAMIC(CCom, CDialog)
CCom::CCom(CWnd* pParent /*=NULL*/)
: CDialog(CCom::IDD, pParent)

{
m_bOpenCom = FALSE;
m_nComNo = 0;
m_nRate = 9600;
m_nParity = NOPARITY;//NONE
m_nData = 8;
m_nStop = ONESTOPBIT;//1
}CCom::~CCom()
{
}void CCom::DoDataExchange(CDataExchange* pDX)
{
CDialog::DoDataExchange(pDX);
DDX_Control(pDX, IDC_COMBO_COM_NO, m_cbCom);
DDX_Control(pDX, IDC_COMBO_COM_RATE, m_cb_Rate);
DDX_Control(pDX, IDC_COMBO_COM_PARITY, m_cb_Parity);
DDX_Control(pDX, IDC_COMBO_DATE, m_cb_Data);
DDX_Control(pDX, IDC_COMBO_STOP, m_cb_Stop);
}
BEGIN_MESSAGE_MAP(CCom, CDialog)
ON_BN_CLICKED(IDOK, OnBnClickedOk)
END_MESSAGE_MAP()
// CCom 消息处理程序BOOL CCom::OnInitDialog()
{
CDialog::OnInitDialog();
InitComBox();
return TRUE;  // return TRUE unless you set the focus to a control
// 异常: OCX 属性页应返回 FALSE
}
//
void CCom::InitComBox(void)
{
//m_cbCom.Clear();
m_cbCom.InsertString(0,"COM 1");
m_cbCom.InsertString(1,"COM 2");
m_cbCom.InsertString(2,"COM 3");
m_cbCom.InsertString(3,"COM 4");
m_cbCom.SetCurSel(m_nComNo);
//
//m_cb_Rate.Clear();
m_cb_Rate.InsertString(0,"1200");
m_cb_Rate.InsertString(1,"2400");
m_cb_Rate.InsertString(2,"4800");
m_cb_Rate.InsertString(3,"9600"); switch(m_nRate)
{
case 1200:
m_cb_Rate.SetCurSel(0);
break;
case 2400:
m_cb_Rate.SetCurSel(1);
break;
case 4800:
m_cb_Rate.SetCurSel(2);
break;
case 9600:
m_cb_Rate.SetCurSel(3);
break; default:
break;
} //
//m_cb_Data.Clear();
m_cb_Data.InsertString(0,"4");
m_cb_Data.InsertString(1,"5");
m_cb_Data.InsertString(2,"6");
m_cb_Data.InsertString(3,"7");
m_cb_Data.InsertString(4,"8");
m_cb_Data.SetCurSel(m_nData-4);
//
//m_cb_Parity.Clear();
m_cb_Parity.InsertString(0,"NONE");
m_cb_Parity.InsertString(1,"ODD");
m_cb_Parity.InsertString(2,"EVEN");
m_cb_Parity.InsertString(3,"MARK");
m_cb_Parity.InsertString(4,"SPACE");
m_cb_Parity.SetCurSel(m_nParity);
//
//m_cb_Stop.Clear();
m_cb_Stop.AddString("1");
m_cb_Stop.AddString("1.5");
m_cb_Stop.AddString("2");
m_cb_Stop.SetCurSel(m_nStop);}
void CCom::OnBnClickedOk()
{
UpdateData(TRUE); m_nComNo = m_cbCom.GetCurSel();
switch(m_cb_Rate.GetCurSel())
{
case 0:
m_nRate = 1200;
break;

case 1:
m_nRate = 2400;
break;
case 2:
m_nRate = 4800;
break;
case 3:
m_nRate = 9600;
break;
default:
break;
}
m_nParity = m_cb_Parity.GetCurSel();
m_nData = m_cb_Data.GetCurSel() + 4;
m_nStop = m_cb_Stop.GetCurSel(); if(m_bOpenCom)
Close();
if(OpenCOM(m_nComNo+1) == INVALID_HANDLE_VALUE)
{
AfxMessageBox("打开串口失败!");
}
OnOK();
}//////////////////////////////////////////////////////////////
//功能:     打开串口
//入口:     iPort:串口号
//返回:     >=0 打开后的串口指针,
//          INVALID_HANDLE_VALUE(-1) 失败
///////////////////////////////////////////////////////////////
HANDLE CCom::OpenCOM(int iPort)
{
    char szPortName[20];   wsprintf(szPortName, "COM%d", iPort);
    HANDLE hTemp = CreateFile( szPortName,
GENERIC_READ | GENERIC_WRITE,
0,
NULL,
OPEN_EXISTING,
FILE_ATTRIBUTE_NORMAL | FILE_FLAG_OVERLAPPED,
NULL);    if (hTemp == INVALID_HANDLE_VALUE)
{
    return INVALID_HANDLE_VALUE;
    }
    m_hHandle = hTemp;
    
    SetCommMask(m_hHandle, EV_RXCHAR);
    SetupComm(m_hHandle, 4096, 4096); //
    PurgeComm(m_hHandle, PURGE_TXABORT | PURGE_RXABORT | //清理串口
              PURGE_TXCLEAR | PURGE_RXCLEAR);    COMMTIMEOUTS CommTimeOuts;
    CommTimeOuts.ReadIntervalTimeout = MAXDWORD;
    CommTimeOuts.ReadTotalTimeoutMultiplier = 2;
    CommTimeOuts.ReadTotalTimeoutConstant = 2000;
    CommTimeOuts.WriteTotalTimeoutMultiplier = 2;
    CommTimeOuts.WriteTotalTimeoutConstant = 800;
    if (!SetCommTimeouts(m_hHandle, &CommTimeOuts))
    {
        Close();
        return INVALID_HANDLE_VALUE;
    }    DCB PortDCB;
   // Set the default settings
    if (!GetCommState(m_hHandle, &PortDCB))
    {
        Close();
    return INVALID_HANDLE_VALUE;
    }
PortDCB.DCBlength = sizeof(DCB);
PortDCB.BaudRate = m_nRate;
    PortDCB.ByteSize = m_nData;
PortDCB.Parity   = m_nParity;
    PortDCB.StopBits = m_nStop;
    if (!SetCommState(m_hHandle, &PortDCB))
{
        Close();
     return INVALID_HANDLE_VALUE;
} return m_hHandle;
}
///////////////////////////////////////////////////////////////
//功能:     关闭端口
//
///////////////////////////////////////////////////////////////
void CCom::Close()
{
if (m_hHandle == INVALID_HANDLE_VALUE)
return;
    SetCommMask(m_hHandle, 0 );
    // purge any outstanding reads/writes and close device handle
    PurgeComm(m_hHandle, PURGE_TXABORT | PURGE_RXABORT |
              PURGE_TXCLEAR | PURGE_RXCLEAR);
CloseHandle(m_hHandle);
    m_hHandle = INVALID_HANDLE_VALUE;
}///////////////////////////////////////////////////////////////
//功能:     从端口读数据
//
///////////////////////////////////////////////////////////////
int CCom::Read(char *buffer, int iMaxLength)
{
BOOL       fReadStat ;
COMSTAT    ComStat ;
DWORD      dwErrorFlags;
DWORD      dwLength;
OVERLAPPED osRead; memset(&osRead, 0, sizeof(OVERLAPPED));
if (m_hHandle == INVALID_HANDLE_VALUE)
return 0;
// only try to read number of bytes in queue
ClearCommError(m_hHandle, &dwErrorFlags, &ComStat);
dwLength = min((DWORD)iMaxLength, ComStat.cbInQue); if (dwLength<=0) return 0;
fReadStat = ReadFile(m_hHandle, buffer, dwLength, &dwLength, &osRead) ;
if (!fReadStat)
{
if (GetLastError() == ERROR_IO_PENDING)
{
while (!GetOverlappedResult(m_hHandle, &osRead, &dwLength, true))
{
if (GetLastError() == ERROR_IO_INCOMPLETE) // normal result if not finished
continue;
else
{
// an error occurred, try to recover
ClearCommError(m_hHandle, &dwErrorFlags, &ComStat ) ;
                    return 0;
}
}
}
else
{
// some other error occurred
ClearCommError(m_hHandle, &dwErrorFlags, &ComStat ) ;
return 0;
}
}
return (int)dwLength;
}
///////////////////////////////////////////////////////////////
//功能:     写数据到端口
//
///////////////////////////////////////////////////////////////
int CCom::Write(char *buffer, int iLength)
{
BOOL        fWriteStat;
DWORD       dwBytesWritten;
DWORD       dwErrorFlags;
DWORD       dwBytesSent;
COMSTAT     ComStat;
OVERLAPPED  osWrite; if (m_hHandle == INVALID_HANDLE_VALUE)
return 0; memset(&osWrite, 0, sizeof(OVERLAPPED));
fWriteStat = WriteFile(m_hHandle, buffer, (DWORD)iLength, &dwBytesWritten, &osWrite); dwBytesSent = dwBytesWritten;
if (!fWriteStat)
{
     dwBytesSent = 0;
if(GetLastError() == ERROR_IO_PENDING)
{
while (!GetOverlappedResult(m_hHandle, &osWrite, &dwBytesWritten, true))
{
if (GetLastError() == ERROR_IO_INCOMPLETE)
{
// normal result if not finished
dwBytesSent += dwBytesWritten;
continue;
}
else
{
// an error occurred, try to recover
ClearCommError(m_hHandle, &dwErrorFlags, &ComStat) ;
break;
}
}
dwBytesSent += dwBytesWritten;
}
else
{
// some other error occurred
ClearCommError(m_hHandle, &dwErrorFlags, &ComStat) ;
}
}
return (int)dwBytesSent;
}