CSerialPort類解析

CSerialPort類的功能及成員函數介紹

CSerialPort類是免費提供的串口累，Codeguru是一個非常不錯的源代碼網站

CSerialPort類支持線連接（非MODEM）的串口編程操作。

CSerialPort類是基於多線程的，其工作流程如下：首先設置好串口參數，再開啓串口檢測工作線程，串口檢測工作線程檢測到串口接收到的數據、流控制事件或其他串口事件後，就以消息方式通知主程序，激發消息處理函數來進行數據處理，這是對接受數據而言的，發送數據可直接向串口發送。

CSerialPort類定義的消息如表

消息名稱	消息號	功能說明
WM_COMM_BREAK_DETECTED	WM_USER+1	檢測到輸入中斷
WM_COMM_CTS_DETECTED	WM_USER+2	檢測到CTS（清除發送）信號狀態改變
WM_COMM_DSR_DETECTED	WM_USER+3	檢測到DSR（數據設備準備就緒）信號狀態改變
WM_COMM_ERR_DETECTED	WM_USER+4	發生線狀態錯誤（包括CE_FRAME，CE_OVERRUN，和CE_RXPARITY）
WM_COMM_RING_DETECTED	WM_USER+5	檢測到響鈴指示信號
WM_COMM_RLSD_DETECTED	WM_USER+6	檢測到RLSD（接收線信號）狀態改變
WM_COMM_RXCHAR	WM_USER+7	接收到一個字符並已放入接受緩衝區
WM_COMM_RXFLAG_DETECTED	WM_USER+8	檢測到接受到字符（該字符已放入接受緩衝區）事件
WM_COMM_TXEMPTY_DETECTED	WM_USER+9	檢測到發送緩衝區最後一個字符已經被髮送

介紹幾個經常用到的函數：
1、串口初始化函數InitPort

BOOL CSerialPort::InitPort(CWnd *pPortOwner,    // the owner (CWnd) of the port (receives message) 
                           UINT  portnr,        // portnumber (1..4) 
                           UINT  baud,            // baudrate 
                           char  parity,        // parity 
                           UINT  databits,        // databits 
                           UINT  stopbits,        // stopbits 
                           DWORD dwCommEvents,    // EV_RXCHAR, EV_CTS etc 
                           UINT  writebuffersize)    // size to the writebuffer 
{ 
    assert(portnr > 0 && portnr < 5); 
    assert(pPortOwner != NULL); 
 
    // if the thread is alive: Kill 
    if (m_bThreadAlive) 
    { 
        do 
        { 
            SetEvent(m_hShutdownEvent); 
        } 
        while (m_bThreadAlive); 
        TRACE("Thread ended\n"); 
    } 
 
    // create events 
    if (m_ov.hEvent != NULL) 
        ResetEvent(m_ov.hEvent); 
    m_ov.hEvent = CreateEvent(NULL, TRUE, FALSE, NULL); 
 
    if (m_hWriteEvent != NULL) 
        ResetEvent(m_hWriteEvent); 
    m_hWriteEvent = CreateEvent(NULL, TRUE, FALSE, NULL); 
 
    if (m_hShutdownEvent != NULL) 
        ResetEvent(m_hShutdownEvent); 
    m_hShutdownEvent = CreateEvent(NULL, TRUE, FALSE, NULL); 
 
    // initialize the event objects 
    m_hEventArray[0] = m_hShutdownEvent;    // highest priority 
    m_hEventArray[1] = m_ov.hEvent; 
    m_hEventArray[2] = m_hWriteEvent; 
 
    // initialize critical section 
    InitializeCriticalSection(&m_csCommunicationSync); 
 
    // set buffersize for writing and save the owner 
    m_pOwner = pPortOwner; 
 
    if (m_szWriteBuffer != NULL) 
        delete [] m_szWriteBuffer; 
    m_szWriteBuffer = new char[writebuffersize]; 
 
    m_nPortNr = portnr; 
 
    m_nWriteBufferSize = writebuffersize; 
    m_dwCommEvents = dwCommEvents; 
 
    BOOL bResult = FALSE; 
    char *szPort = new char[50]; 
    char *szBaud = new char[50]; 
 
    // now it critical! 
    EnterCriticalSection(&m_csCommunicationSync); 
 
    // if the port is already opened: close it 
    if (m_hComm != NULL) 
    { 
        CloseHandle(m_hComm); 
        m_hComm = NULL; 
    } 
 
    // prepare port strings 
    sprintf(szPort, "COM%d", portnr); 
    sprintf(szBaud, "baud=%d parity=%c data=%d stop=%d", baud, parity, databits, stopbits); 
 
    // get a handle to the port 
    m_hComm = CreateFile(szPort,                        // communication port string (COMX) 
                         GENERIC_READ | GENERIC_WRITE,    // read/write types 
                         0,                                // comm devices must be opened with exclusive access 
                         NULL,                            // no security attributes 
                         OPEN_EXISTING,                    // comm devices must use OPEN_EXISTING 
                         FILE_FLAG_OVERLAPPED,            // Async I/O 
                         0);                            // template must be 0 for comm devices 
 
    if (m_hComm == INVALID_HANDLE_VALUE) 
    { 
        // port not found 
        delete [] szPort; 
        delete [] szBaud; 
 
        return FALSE; 
    } 
 
    // set the timeout values 
    m_CommTimeouts.ReadIntervalTimeout = 1000; 
    m_CommTimeouts.ReadTotalTimeoutMultiplier = 1000; 
    m_CommTimeouts.ReadTotalTimeoutConstant = 1000; 
    m_CommTimeouts.WriteTotalTimeoutMultiplier = 1000; 
    m_CommTimeouts.WriteTotalTimeoutConstant = 1000; 
 
    // configure 
    if (SetCommTimeouts(m_hComm, &m_CommTimeouts)) 
    { 
        if (SetCommMask(m_hComm, dwCommEvents)) 
        { 
            if (GetCommState(m_hComm, &m_dcb)) 
            { 
                m_dcb.fRtsControl = RTS_CONTROL_ENABLE;        // set RTS bit high! 
                if (BuildCommDCB(szBaud, &m_dcb)) 
                { 
                    if (SetCommState(m_hComm, &m_dcb)) 
                        ; // normal operation... continue 
                    else 
                        ProcessErrorMessage("SetCommState()"); 
                } 
                else 
                    ProcessErrorMessage("BuildCommDCB()"); 
            } 
            else 
                ProcessErrorMessage("GetCommState()"); 
        } 
        else 
            ProcessErrorMessage("SetCommMask()"); 
    } 
    else 
        ProcessErrorMessage("SetCommTimeouts()"); 
 
    delete [] szPort; 
    delete [] szBaud; 
 
    // flush the port 
    PurgeComm(m_hComm, PURGE_RXCLEAR | PURGE_TXCLEAR | PURGE_RXABORT | PURGE_TXABORT); 
 
    // release critical section 
    LeaveCriticalSection(&m_csCommunicationSync); 
 
    TRACE("Initialisation for communicationport %d completed.\nUse Startmonitor to communicate.\n", portnr); 
 
    return TRUE; 
}

這個函數是用來初始化串口的，即設置串口的通信參數：需要打開的串口號、波特率、奇偶校驗方式、數據位、停止位，這裏還可以用來進行事件的設定。

如果串口初始化成功，就返回TRUE，若串口被其他設備佔用、不存在或存在其他股佔，就返回FALSE，編程者可以在這兒提示串口操作是否成功。

如果在當前主串口調用這個函數，那麼pPortOwner可用this指針表示，串口號在函數中做了限制，只能用1，2，3和4四個串口號，而事實上在編程時可能用到更多串口號，可以通過通過註釋掉本函數中的“assert(portur>0&&portnr<5)”語句取消對串口號的限制。

2、啓動串口通信監測線程函數StartMonitoring（）

串口初始化成功後，就可以調用BOOL StartMonitoring（）來啓動串口檢測線程，線程啓動成功，發揮TRUE

BOOL CSerialPort::StartMonitoring()

{

if (!(m_Thread = AfxBeginThread(CommThread, this)))

return FALSE;

TRACE("Thread started\n");

return TRUE;
}

3、暫停或停止監測線程函數StopMonitoring（）

該函數暫停或停止串口檢測，要注意的是，調用該函數後，串口資源仍然被佔用
// Suspend the comm thread
//
BOOL CSerialPort::StopMonitoring()
{
     TRACE("Thread suspended\n");
     m_Thread->SuspendThread();
     return TRUE;
}

4、關閉串口函數ClosePort（）

該函數功能是關閉串口，釋放串口資源，調用該函數後，如果要繼續使用串口，還需要調用InitPort（）函數

5、通過串口發送字符/寫串口函數WriteToPort（）

該函數完成寫串口功能，即向串口發送字符。

// Write a string to the port

void CSerialPort::WriteToPort(char *string)

{

assert(m_hComm != 0);

memset(m_szWriteBuffer, 0, sizeof(m_szWriteBuffer));

strcpy(m_szWriteBuffer, string);

// set event for write

SetEvent(m_hWriteEvent);

}

以上是常用的函數介紹，熟悉該類的使用後，可以仔細看看其他函數，對上面介紹的函數，在對串口資源的使用上要記住一下三點：

l 打開串口用調用InitPort（）和StartMonitoring（）；關閉串口用StopMonitoring（）和ClosePort（）而且以上函數的調用順序不能亂

l 通過串口發送字符調用函數WriteToPort（）

l 接受串口收到的字符需要自己編寫WM_COMM_RXCHAR消息處理函數，需要手工添加。

操作：

首先，需要操作一個串口，所以只需要定義1個類對象就可以了，如要操作多個串口，則要爲每個串口均定一個類對象，這可以通過數據方式來實現，這裏定義的類對象爲m_SerialPort，再定義一個布爾變量m_bSerialPortOpened用來標誌串口是否打開。

在CserialPort類中有多個串口事件可以響應，在一般串口編程中，只需要處理WM_COMM_RXCHAR消息就可以了，該類所有的消息均需要人工添加消息處理函數，將處理函數名定義爲OnComm（），首先在SerialPortTestDlg.h（頭文件）中添加串口字符接受消息WM_COMM_RXCHAR（串口接受緩衝區內有一個字符）的響應函數聲明：

//Generated message map funnctions

//{{AFX_MSG(CSCportTestView)

afx_msg long OnComm(WPARAM ch, LPARAM port);

//}}AFX_MSG

然後在，SerilPortTestDlg.cpp文件中進行WM_COMM_RXCHAR消息映射

BEGIN_MESSAE_MAP(CSerialPortTestDlg, CDialog)s

//{{AFX_MSG_MAP(CSerialPortTestDlg)

ON_MESSAGE(WM_COMM_RXCHAR, OnComm)

//}}AFX_MSG_MAP

END_MESSAGE_MAP()

接着，在SerialPortTestDlg.cpp文件中加入函數OnComm（）的實現，並在其中完成對節誒受到的字符的處理，將接收到的字符顯示在接受編輯框中：

long CSerialPortTestDlg::OnComm(WPARAM ch, LPARAM port)

{

m_strEditReceiveMsg += ch;

UpdateData(FLASE);//將接收到的字符顯示在接受編輯框中

returne 0;

}

說明：WPARAM、LPARAM類型是多態數據類型，在WIN32中爲32位，支持多種數據類型，根據需要自動適應，這樣，程序有很強的適應性，再次，我們可以分貝理解爲char和integer類型數據，每當串口接受緩衝區內有一個字符時，就會產生一個WM_COMM_RXCHAR消息，除法OnComm（）函數，這時就可以在函數中進行數據處理，所以，這個消息就是整個程序的源頭。

雖然CSerialPort類是一個非常好的類，但畢竟只是集中了作者一個人的智慧和經驗，他也有許多缺陷，

n 原類只能發送字符（ASCII文本）不能處理二進制發送（也就是不能發送0X00）

n 該類不能很好的釋放串口

n 存在內存泄漏

可以進行如下改進

改進一、ASCII文本和二進制數據發送方式兼容

CSerialPort類中只有一個發送函數WriteToPort（）

// Write a string to the port

void CSerialPort::WriteToPort(char *string)

{

assert(m_hComm != 0);

memset(m_szWriteBuffer, 0, sizeof(m_szWriteBuffer));

strcpy(m_szWriteBuffer, string);

// set event for write

SetEvent(m_hWriteEvent);

}

調用上面的函數就只能用字符串方式，而c語言中，空字符（NULL，其中ASCII碼值爲0，即通常所說的十六禁止0x00字符），是串結束符，當檢測到NULL字符後，就認爲該字符串結束了，所以0x00字符以ASCII文本方式是不能從串口發送出去的，那麼解決這一問題的方法就是用二進制發送，其實這裏說的二進制，只不過是不以我們通常所說的“可見”或“能顯示的字符”發送，比如，要發如下的一組值：

char chSend[5]={0x33,0x96,0x00,0x31,0xf1};

下面來對類做一些改進，解決這個問題，原理就是用字符數據來發送數據，並在發送時指定其長度，這樣，數據沒有發送完，發送過程就不會停止，CSerialPort類是用API函數編寫的在，只要在WriteFile()函數中指定其實際要發送的長度，就可以將數據全部發送出去：

實現步驟如下：

1、在SerialPort.h文件中爲CSerialPort類添加一個整形public成員變量，：int m_nWriteSize；用於指定發送字符數據的長度

添加三個發送函數

h文件：

[cpp] view plain copy print ?

#ifndef __SERIALPORT_H__
#define __SERIALPORT_H__
#define WM_COMM_BREAK_DETECTED WM_USER+1 // A break was detected on input.
#define WM_COMM_CTS_DETECTED WM_USER+2 // The CTS (clear-to-send) signal changed state.
#define WM_COMM_DSR_DETECTED WM_USER+3 // The DSR (data-set-ready) signal changed state.
#define WM_COMM_ERR_DETECTED WM_USER+4 // A line-status error occurred. Line-status errors are CE_FRAME, CE_OVERRUN, and CE_RXPARITY.
#define WM_COMM_RING_DETECTED WM_USER+5 // A ring indicator was detected.
#define WM_COMM_RLSD_DETECTED WM_USER+6 // The RLSD (receive-line-signal-detect) signal changed state.
#define WM_COMM_RXCHAR WM_USER+7 // A character was received and placed in the input buffer.
#define WM_COMM_RXFLAG_DETECTED WM_USER+8 // The event character was received and placed in the input buffer.
#define WM_COMM_TXEMPTY_DETECTED WM_USER+9 // The last character in the output buffer was sent.
class CSerialPort
{
public:
void ClosePort();
void WriteToPort(LPCTSTR string, int n);
void WriteToPort(LPCTSTR string);
void WriteToPort(char *string, int n);
CSerialPort();
virtual ~CSerialPort();
BOOL InitPort(CWnd *pPortOwner, // the owner (CWnd) of the port (receives message)
UINT portnr, // portnumber (1..4)
UINT baud, // baudrate
char parity, // parity
UINT databits, // databits
UINT stopbits, // stopbits
DWORD dwCommEvents, // EV_RXCHAR, EV_CTS etc
UINT writebuffersize); // size to the writebuffer
BOOL StartMonitoring();
BOOL RestartMonitoring();
BOOL StopMonitoring();
DWORD GetWriteBufferSize();
DWORD GetCommEvents();
DCB GetDCB();
void WriteToPort(char *string);
int m_nWriteSize;
protected:
// protected memberfunctions
void ProcessErrorMessage(char *ErrorText);
static UINT CommThread(LPVOID pParam);
static void ReceiveChar(CSerialPort *port, COMSTAT comstat);
static void WriteChar(CSerialPort *port);
// thread
CWinThread *m_Thread;
// synchronisation objects
CRITICAL_SECTION m_csCommunicationSync;
BOOL m_bThreadAlive;
// handles
HANDLE m_hShutdownEvent;
HANDLE m_hComm;
HANDLE m_hWriteEvent;
// Event array.
// One element is used for each event. There are two event handles for each port.
// A Write event and a receive character event which is located in the overlapped structure (m_ov.hEvent).
// There is a general shutdown when the port is closed.
HANDLE m_hEventArray[3];
// structures
OVERLAPPED m_ov;
COMMTIMEOUTS m_CommTimeouts;
DCB m_dcb;
// owner window
CWnd *m_pOwner;
// misc
UINT m_nPortNr;
char *m_szWriteBuffer;
DWORD m_dwCommEvents;
DWORD m_nWriteBufferSize;
};
#endif __SERIALPORT_H__

#ifndef __SERIALPORT_H__ 
#define __SERIALPORT_H__ 
 
#define WM_COMM_BREAK_DETECTED        WM_USER+1    // A break was detected on input. 
#define WM_COMM_CTS_DETECTED        WM_USER+2    // The CTS (clear-to-send) signal changed state.  
#define WM_COMM_DSR_DETECTED        WM_USER+3    // The DSR (data-set-ready) signal changed state.  
#define WM_COMM_ERR_DETECTED        WM_USER+4    // A line-status error occurred. Line-status errors are CE_FRAME, CE_OVERRUN, and CE_RXPARITY.  
#define WM_COMM_RING_DETECTED        WM_USER+5    // A ring indicator was detected.  
#define WM_COMM_RLSD_DETECTED        WM_USER+6    // The RLSD (receive-line-signal-detect) signal changed state.  
#define WM_COMM_RXCHAR                WM_USER+7    // A character was received and placed in the input buffer.  
#define WM_COMM_RXFLAG_DETECTED        WM_USER+8    // The event character was received and placed in the input buffer.   
#define WM_COMM_TXEMPTY_DETECTED    WM_USER+9    // The last character in the output buffer was sent.   
 
 
class CSerialPort 
{ 
public: 
    void ClosePort(); 
    void WriteToPort(LPCTSTR string, int n); 
    void WriteToPort(LPCTSTR string); 
    void WriteToPort(char *string, int n); 
    CSerialPort(); 
    virtual        ~CSerialPort(); 
    BOOL        InitPort(CWnd *pPortOwner,    // the owner (CWnd) of the port (receives message) 
                         UINT  portnr,        // portnumber (1..4) 
                         UINT  baud,            // baudrate 
                         char  parity,        // parity 
                         UINT  databits,        // databits 
                         UINT  stopbits,        // stopbits 
                         DWORD dwCommEvents,    // EV_RXCHAR, EV_CTS etc 
                         UINT  writebuffersize);    // size to the writebuffer 
 
    BOOL        StartMonitoring(); 
    BOOL        RestartMonitoring(); 
    BOOL        StopMonitoring(); 
    DWORD        GetWriteBufferSize(); 
    DWORD        GetCommEvents(); 
    DCB            GetDCB(); 
 
    void        WriteToPort(char *string); 
    int m_nWriteSize; 
 
protected: 
    // protected memberfunctions 
    void        ProcessErrorMessage(char *ErrorText); 
    static UINT    CommThread(LPVOID pParam); 
    static void    ReceiveChar(CSerialPort *port, COMSTAT comstat); 
    static void    WriteChar(CSerialPort *port); 
 
    // thread 
    CWinThread            *m_Thread; 
 
    // synchronisation objects 
    CRITICAL_SECTION    m_csCommunicationSync; 
    BOOL                m_bThreadAlive; 
 
    // handles 
    HANDLE                m_hShutdownEvent; 
    HANDLE                m_hComm; 
    HANDLE                m_hWriteEvent; 
 
    // Event array. 
    // One element is used for each event. There are two event handles for each port. 
    // A Write event and a receive character event which is located in the overlapped structure (m_ov.hEvent). 
    // There is a general shutdown when the port is closed. 
    HANDLE                m_hEventArray[3]; 
 
    // structures 
    OVERLAPPED            m_ov; 
    COMMTIMEOUTS        m_CommTimeouts; 
    DCB                    m_dcb; 
 
    // owner window 
    CWnd                *m_pOwner; 
 
    // misc 
    UINT                m_nPortNr; 
    char                *m_szWriteBuffer; 
    DWORD                m_dwCommEvents; 
    DWORD                m_nWriteBufferSize; 
}; 
 
#endif __SERIALPORT_H__

cpp文件：

[cpp] view plain copy print ?

CSerialPort.cpp
/*
** FILENAME CSerialPort.cpp
**
** PURPOSE This class can read, write and watch one serial port.
** It sends messages to its owner when something happends on the port
** The class creates a thread for reading and writing so the main
** program is not blocked.
**
** CREATION DATE 15-09-1997
** LAST MODIFICATION 12-11-1997
**
** AUTHOR Remon Spekreijse
**
**
*/
#include "stdafx.h"
#include "CSerialPort.h"
#include <assert.h>
//
// Constructor
//
CSerialPort::CSerialPort()
{
m_hComm = NULL;
// initialize overlapped structure members to zero
m_ov.Offset = 0;
m_ov.OffsetHigh = 0;
// create events
m_ov.hEvent = NULL;
m_hWriteEvent = NULL;
m_hShutdownEvent = NULL;
m_szWriteBuffer = NULL;
m_bThreadAlive = FALSE;
m_nWriteSize = 0;
}
//
// Delete dynamic memory
//
CSerialPort::~CSerialPort()
{
do
{
SetEvent(m_hShutdownEvent);
}
while (m_bThreadAlive);
TRACE("Thread ended\n");
delete [] m_szWriteBuffer;
}
//
// Initialize the port. This can be port 1 to 4.
//
BOOL CSerialPort::InitPort(CWnd *pPortOwner, // the owner (CWnd) of the port (receives message)
UINT portnr, // portnumber (1..4)
UINT baud, // baudrate
char parity, // parity
UINT databits, // databits
UINT stopbits, // stopbits
DWORD dwCommEvents, // EV_RXCHAR, EV_CTS etc
UINT writebuffersize) // size to the writebuffer
{
assert(portnr > 0 && portnr < 5);
assert(pPortOwner != NULL);
// if the thread is alive: Kill
if (m_bThreadAlive)
{
do
{
SetEvent(m_hShutdownEvent);
}
while (m_bThreadAlive);
TRACE("Thread ended\n");
}
// create events
if (m_ov.hEvent != NULL)
ResetEvent(m_ov.hEvent);
else
m_ov.hEvent = CreateEvent(NULL, TRUE, FALSE, NULL);
if (m_hWriteEvent != NULL)
ResetEvent(m_hWriteEvent);
else
m_hWriteEvent = CreateEvent(NULL, TRUE, FALSE, NULL);
if (m_hShutdownEvent != NULL)
ResetEvent(m_hShutdownEvent);
else
m_hShutdownEvent = CreateEvent(NULL, TRUE, FALSE, NULL);
// initialize the event objects
m_hEventArray[0] = m_hShutdownEvent; // highest priority
m_hEventArray[1] = m_ov.hEvent;
m_hEventArray[2] = m_hWriteEvent;
// initialize critical section
InitializeCriticalSection(&m_csCommunicationSync);
// set buffersize for writing and save the owner
m_pOwner = pPortOwner;
if (m_szWriteBuffer != NULL)
delete [] m_szWriteBuffer;
m_szWriteBuffer = new char[writebuffersize];
m_nPortNr = portnr;
m_nWriteBufferSize = writebuffersize;
m_dwCommEvents = dwCommEvents;
BOOL bResult = FALSE;
char *szPort = new char[50];
char *szBaud = new char[50];
// now it critical!
EnterCriticalSection(&m_csCommunicationSync);
// if the port is already opened: close it
if (m_hComm != NULL)
{
CloseHandle(m_hComm);
m_hComm = NULL;
}
// prepare port strings
sprintf(szPort, "COM%d", portnr);
sprintf(szBaud, "baud=%d parity=%c data=%d stop=%d", baud, parity, databits, stopbits);
// get a handle to the port
m_hComm = CreateFile(szPort, // communication port string (COMX)
GENERIC_READ | GENERIC_WRITE, // read/write types
0, // comm devices must be opened with exclusive access
NULL, // no security attributes
OPEN_EXISTING, // comm devices must use OPEN_EXISTING
FILE_FLAG_OVERLAPPED, // Async I/O
0); // template must be 0 for comm devices
if (m_hComm == INVALID_HANDLE_VALUE)
{
// port not found
delete [] szPort;
delete [] szBaud;
return FALSE;
}
// set the timeout values
m_CommTimeouts.ReadIntervalTimeout = 1000;
m_CommTimeouts.ReadTotalTimeoutMultiplier = 1000;
m_CommTimeouts.ReadTotalTimeoutConstant = 1000;
m_CommTimeouts.WriteTotalTimeoutMultiplier = 1000;
m_CommTimeouts.WriteTotalTimeoutConstant = 1000;
// configure
if (SetCommTimeouts(m_hComm, &m_CommTimeouts))
{
if (SetCommMask(m_hComm, dwCommEvents))
{
if (GetCommState(m_hComm, &m_dcb))
{
m_dcb.fRtsControl = RTS_CONTROL_ENABLE; // set RTS bit high!
if (BuildCommDCB(szBaud, &m_dcb))
{
if (SetCommState(m_hComm, &m_dcb))
; // normal operation... continue
else
ProcessErrorMessage("SetCommState()");
}
else
ProcessErrorMessage("BuildCommDCB()");
}
else
ProcessErrorMessage("GetCommState()");
}
else
ProcessErrorMessage("SetCommMask()");
}
else
ProcessErrorMessage("SetCommTimeouts()");
delete [] szPort;
delete [] szBaud;
// flush the port
PurgeComm(m_hComm, PURGE_RXCLEAR | PURGE_TXCLEAR | PURGE_RXABORT | PURGE_TXABORT);
// release critical section
LeaveCriticalSection(&m_csCommunicationSync);
TRACE("Initialisation for communicationport %d completed.\nUse Startmonitor to communicate.\n", portnr);
return TRUE;
}
//
// The CommThread Function.
//
UINT CSerialPort::CommThread(LPVOID pParam)
{
// Cast the void pointer passed to the thread back to
// a pointer of CSerialPort class
CSerialPort *port = (CSerialPort *)pParam;
// Set the status variable in the dialog class to
// TRUE to indicate the thread is running.
port->m_bThreadAlive = TRUE;
// Misc. variables
DWORD BytesTransfered = 0;
DWORD Event = 0;
DWORD CommEvent = 0;
DWORD dwError = 0;
COMSTAT comstat;
BOOL bResult = TRUE;
// Clear comm buffers at startup
if (port->m_hComm) // check if the port is opened
PurgeComm(port->m_hComm, PURGE_RXCLEAR | PURGE_TXCLEAR | PURGE_RXABORT | PURGE_TXABORT);
// begin forever loop. This loop will run as long as the thread is alive.
for (;;)
{
// Make a call to WaitCommEvent(). This call will return immediatly
// because our port was created as an async port (FILE_FLAG_OVERLAPPED
// and an m_OverlappedStructerlapped structure specified). This call will cause the
// m_OverlappedStructerlapped element m_OverlappedStruct.hEvent, which is part of the m_hEventArray to
// be placed in a non-signeled state if there are no bytes available to be read,
// or to a signeled state if there are bytes available. If this event handle
// is set to the non-signeled state, it will be set to signeled when a
// character arrives at the port.
// we do this for each port!
bResult = WaitCommEvent(port->m_hComm, &Event, &port->m_ov);
if (!bResult)
{
// If WaitCommEvent() returns FALSE, process the last error to determin
// the reason..
switch (dwError = GetLastError())
{
case ERROR_IO_PENDING:
{
// This is a normal return value if there are no bytes
// to read at the port.
// Do nothing and continue
break;
}
case 87:
{
// Under Windows NT, this value is returned for some reason.
// I have not investigated why, but it is also a valid reply
// Also do nothing and continue.
break;
}
default:
{
// All other error codes indicate a serious error has
// occured. Process this error.
port->ProcessErrorMessage("WaitCommEvent()");
break;
}
}
}
else
{
// If WaitCommEvent() returns TRUE, check to be sure there are
// actually bytes in the buffer to read.
//
// If you are reading more than one byte at a time from the buffer
// (which this program does not do) you will have the situation occur
// where the first byte to arrive will cause the WaitForMultipleObjects()
// function to stop waiting. The WaitForMultipleObjects() function
// resets the event handle in m_OverlappedStruct.hEvent to the non-signelead state
// as it returns.
//
// If in the time between the reset of this event and the call to
// ReadFile() more bytes arrive, the m_OverlappedStruct.hEvent handle will be set again
// to the signeled state. When the call to ReadFile() occurs, it will
// read all of the bytes from the buffer, and the program will
// loop back around to WaitCommEvent().
//
// At this point you will be in the situation where m_OverlappedStruct.hEvent is set,
// but there are no bytes available to read. If you proceed and call
// ReadFile(), it will return immediatly due to the async port setup, but
// GetOverlappedResults() will not return until the next character arrives.
//
// It is not desirable for the GetOverlappedResults() function to be in
// this state. The thread shutdown event (event 0) and the WriteFile()
// event (Event2) will not work if the thread is blocked by GetOverlappedResults().
//
// The solution to this is to check the buffer with a call to ClearCommError().
// This call will reset the event handle, and if there are no bytes to read
// we can loop back through WaitCommEvent() again, then proceed.
// If there are really bytes to read, do nothing and proceed.
bResult = ClearCommError(port->m_hComm, &dwError, &comstat);
if (comstat.cbInQue == 0)
continue;
} // end if bResult
// Main wait function. This function will normally block the thread
// until one of nine events occur that require action.
Event = WaitForMultipleObjects(3, port->m_hEventArray, FALSE, INFINITE);
switch (Event)
{
case 0:
{
// Shutdown event. This is event zero so it will be
// the higest priority and be serviced first.
port->m_bThreadAlive = FALSE;
// Kill this thread. break is not needed, but makes me feel better.
AfxEndThread(100);
break;
}
case 1: // read event
{
GetCommMask(port->m_hComm, &CommEvent);
if (CommEvent & EV_CTS)
::SendMessage(port->m_pOwner->m_hWnd, WM_COMM_CTS_DETECTED, (WPARAM) 0, (LPARAM) port->m_nPortNr);
if (CommEvent & EV_RXFLAG)
::SendMessage(port->m_pOwner->m_hWnd, WM_COMM_RXFLAG_DETECTED, (WPARAM) 0, (LPARAM) port->m_nPortNr);
if (CommEvent & EV_BREAK)
::SendMessage(port->m_pOwner->m_hWnd, WM_COMM_BREAK_DETECTED, (WPARAM) 0, (LPARAM) port->m_nPortNr);
if (CommEvent & EV_ERR)
::SendMessage(port->m_pOwner->m_hWnd, WM_COMM_ERR_DETECTED, (WPARAM) 0, (LPARAM) port->m_nPortNr);
if (CommEvent & EV_RING)
::SendMessage(port->m_pOwner->m_hWnd, WM_COMM_RING_DETECTED, (WPARAM) 0, (LPARAM) port->m_nPortNr);
if (CommEvent & EV_RXCHAR)
// Receive character event from port.
ReceiveChar(port, comstat);
break;
}
case 2: // write event
{
// Write character event from port
WriteChar(port);
break;
}
} // end switch
} // close forever loop
return 0;
}
//
// start comm watching
//
BOOL CSerialPort::StartMonitoring()
{
if (!(m_Thread = AfxBeginThread(CommThread, this)))
return FALSE;
TRACE("Thread started\n");
return TRUE;
}
//
// Restart the comm thread
//
BOOL CSerialPort::RestartMonitoring()
{
TRACE("Thread resumed\n");
m_Thread->ResumeThread();
return TRUE;
}
//
// Suspend the comm thread
//
BOOL CSerialPort::StopMonitoring()
{
TRACE("Thread suspended\n");
m_Thread->SuspendThread();
return TRUE;
}
//
// If there is a error, give the right message
//
void CSerialPort::ProcessErrorMessage(char *ErrorText)
{
char *Temp = new char[200];
LPVOID lpMsgBuf;
FormatMessage(
FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM,
NULL,
GetLastError(),
MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT), // Default language
(LPTSTR) &lpMsgBuf,
0,
NULL
);
sprintf(Temp, "WARNING: %s Failed with the following error: \n%s\nPort: %d\n", (char *)ErrorText, lpMsgBuf, m_nPortNr);
MessageBox(NULL, Temp, "Application Error", MB_ICONSTOP);
LocalFree(lpMsgBuf);
delete[] Temp;
}
//
// Write a character.
//
void CSerialPort::WriteChar(CSerialPort *port)
{
BOOL bWrite = TRUE;
BOOL bResult = TRUE;
DWORD BytesSent = 0;
ResetEvent(port->m_hWriteEvent);
// Gain ownership of the critical section
EnterCriticalSection(&port->m_csCommunicationSync);
if (bWrite)
{
// Initailize variables
port->m_ov.Offset = 0;
port->m_ov.OffsetHigh = 0;
// Clear buffer
PurgeComm(port->m_hComm, PURGE_RXCLEAR | PURGE_TXCLEAR | PURGE_RXABORT | PURGE_TXABORT);
bResult = WriteFile(port->m_hComm, // Handle to COMM Port
port->m_szWriteBuffer, // Pointer to message buffer in calling finction
//原句 strlen((char*)port->m_szWriteBuffer), // Length of message to send
port->m_nWriteSize,//更改後，Length of message to send
&BytesSent, // Where to store the number of bytes sent
&port->m_ov); // Overlapped structure
// deal with any error codes
if (!bResult)
{
DWORD dwError = GetLastError();
switch (dwError)
{
case ERROR_IO_PENDING:
{
// continue to GetOverlappedResults()
BytesSent = 0;
bWrite = FALSE;
break;
}
default:
{
// all other error codes
port->ProcessErrorMessage("WriteFile()");
}
}
}
else
{
LeaveCriticalSection(&port->m_csCommunicationSync);
}
} // end if(bWrite)
if (!bWrite)
{
bWrite = TRUE;
bResult = GetOverlappedResult(port->m_hComm, // Handle to COMM port
&port->m_ov, // Overlapped structure
&BytesSent, // Stores number of bytes sent
TRUE); // Wait flag
LeaveCriticalSection(&port->m_csCommunicationSync);
// deal with the error code
if (!bResult)
{
port->ProcessErrorMessage("GetOverlappedResults() in WriteFile()");
}
} // end if (!bWrite)
// Verify that the data size send equals what we tried to send
//原句 if (BytesSent != strlen((char*)port->m_szWriteBuffer))
if(BytesSent |= port->m_nWriteSize) //修改後，Length of message to send
{
TRACE("WARNING: WriteFile() error.. Bytes Sent: %d; Message Length: %d\n", BytesSent, strlen((char *)port->m_szWriteBuffer));
}
}
//
// Character received. Inform the owner
//
void CSerialPort::ReceiveChar(CSerialPort *port, COMSTAT comstat)
{
BOOL bRead = TRUE;
BOOL bResult = TRUE;
DWORD dwError = 0;
DWORD BytesRead = 0;
unsigned char RXBuff;
for (;;)
{
// Gain ownership of the comm port critical section.
// This process guarantees no other part of this program
// is using the port object.
//添加信息防止死鎖
if(WaitForSingleObject(port->m_hShutdownEvent, 0) == WAIT_OBJECT_0)
return ;
EnterCriticalSection(&port->m_csCommunicationSync);
// ClearCommError() will update the COMSTAT structure and
// clear any other errors.
bResult = ClearCommError(port->m_hComm, &dwError, &comstat);
LeaveCriticalSection(&port->m_csCommunicationSync);
// start forever loop. I use this type of loop because I
// do not know at runtime how many loops this will have to
// run. My solution is to start a forever loop and to
// break out of it when I have processed all of the
// data available. Be careful with this approach and
// be sure your loop will exit.
// My reasons for this are not as clear in this sample
// as it is in my production code, but I have found this
// solutiion to be the most efficient way to do this.
if (comstat.cbInQue == 0)
{
// break out when all bytes have been read
break;
}
EnterCriticalSection(&port->m_csCommunicationSync);
if (bRead)
{
bResult = ReadFile(port->m_hComm, // Handle to COMM port
&RXBuff, // RX Buffer Pointer
1, // Read one byte
&BytesRead, // Stores number of bytes read
&port->m_ov); // pointer to the m_ov structure
// deal with the error code
if (!bResult)
{
switch (dwError = GetLastError())
{
case ERROR_IO_PENDING:
{
// asynchronous i/o is still in progress
// Proceed on to GetOverlappedResults();
bRead = FALSE;
break;
}
default:
{
// Another error has occured. Process this error.
port->ProcessErrorMessage("ReadFile()");
break;
}
}
}
else
{
// ReadFile() returned complete. It is not necessary to call GetOverlappedResults()
bRead = TRUE;
}
} // close if (bRead)
if (!bRead)
{
bRead = TRUE;
bResult = GetOverlappedResult(port->m_hComm, // Handle to COMM port
&port->m_ov, // Overlapped structure
&BytesRead, // Stores number of bytes read
TRUE); // Wait flag
// deal with the error code
if (!bResult)
{
port->ProcessErrorMessage("GetOverlappedResults() in ReadFile()");
}
} // close if (!bRead)
LeaveCriticalSection(&port->m_csCommunicationSync);
// notify parent that a byte was received
::SendMessage((port->m_pOwner)->m_hWnd, WM_COMM_RXCHAR, (WPARAM) RXBuff, (LPARAM) port->m_nPortNr);
} // end forever loop
}
//
// Write a string to the port
//
void CSerialPort::WriteToPort(char *string)
{
assert(m_hComm != 0);
memset(m_szWriteBuffer, 0, sizeof(m_szWriteBuffer));
strcpy(m_szWriteBuffer, string);
m_nWriteSize = strlen(string);
// set event for write
SetEvent(m_hWriteEvent);
}
//
// Return the device control block
//
DCB CSerialPort::GetDCB()
{
return m_dcb;
}
//
// Return the communication event masks
//
DWORD CSerialPort::GetCommEvents()
{
return m_dwCommEvents;
}
//
// Return the output buffer size
//
DWORD CSerialPort::GetWriteBufferSize()
{
return m_nWriteBufferSize;
}
void CSerialPort::WriteToPort(char *string, int n)
{
assert(m_hComm != 0);
memset(m_szWriteBuffer, 0, sizeof(m_szWriteBuffer));
memcpy(m_szWriteBuffer, string, n);
m_nWriteSize = n;
//set event for write
SetEvent(m_hWriteEvent);
}
void CSerialPort::WriteToPort(LPCTSTR string)
{
assert(m_hComm != 0);
memset(m_szWriteBuffer, 0, sizeof(m_szWriteBuffer));
strcpy(m_szWriteBuffer, string);
m_nWriteSize = strlen(string);
//set event for write
SetEvent(m_hWriteEvent);
}
void CSerialPort::WriteToPort(LPCTSTR string, int n)
{
assert(m_hComm != 0);
memset(m_szWriteBuffer, 0, sizeof(m_szWriteBuffer));
memcpy(m_szWriteBuffer, string, n);
m_nWriteSize = n;
//set event for write
SetEvent(m_hWriteEvent);
}
void CSerialPort::ClosePort()
{
if (m_bThreadAlive)
{
MSG message;
while (m_bThreadAlive)
{
if(::PeekMessage(&message, m_pOwner->m_hWnd, 0, 0, PM_REMOVE))
{
::TranslateMessage(&message);
::DispatchMessage(&message);
}
SetEvent(m_hShutdownEvent);
}
TRACE("Thread ended\n");
}
if(m_szWriteBuffer != NULL)
{
delete [] m_szWriteBuffer;
m_szWriteBuffer = NULL;
}
if(m_hComm)
{
CloseHandle(m_hComm);
m_hComm = NULL;
}
}

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