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深入浅出Win32多线程程序设计综合实例

本章我们将以工业节制和嵌入式系统中运用极为广泛的串口通信为例讲述多线程的范例利用。

而收集通信也是多线程利用最广泛的领域之一,以是本章的着末一节也将对多线程收集通信进行简短的描述。

1.串口通信

在工业节制系统中,工控机(一样平常都基于PC Windows平台)常常必要与单片机经由过程串口进行通信。是以,操作和应用PC的串口成为大年夜多半单片机、嵌入式系统领域工程师必须具备的能力。

串口的应用必要经由过程三个步骤来完成的:

(1) 打开通信端口;

(2) 初始化串口,设置波特率、数据位、竣事位、奇偶校验等参数。为了给读者一个直不雅的印象,下图从Windows的"节制面板->系统->设备管理器->通信端口(COM1)"打开COM的设置窗口:

(3) 读写串口。

在WIN32平台下,对通信端口进行操作跟基础的文件操作一样。

创建/打开COM资本

下列函数要是调用成功,则返回一个标识通信端口的句柄,否则返回-1:

HADLE CreateFile(PCTSTR lpFileName, //通信端口名,如"COM1"

Word dwDesiredaccess, //对资本的造访类型

WORD dwShareMode, //指定共享模式,COM不能共享,该参数为0

PSECURITY_ATTRIBUTES lpSecurityAttributes,

//安然描述符指针,可为NULL

WORD dwCreationDisposition, //创建要领

WORD dwFlagsAndAttributes, //文件属性,可为NULL

HANDLE hTemplateFile //模板文件句柄,置为NULL

);

得到/设置COM属性

下列函数可以得到COM口的设备节制块,从而得到相关参数:

BOOL WINAPI GetCommState(

HANDLE hFile, //标识通信端口的句柄

LPDCB lpDCB //指向一个设备节制块(DCB布局)的指针

);

要是要调剂通信端口的参数,则必要从新设置设置设备摆设摆设设备节制块,再用WIN32 API SetCommState()函数进行设置:

BOOL SetCommState(

HANDLE hFile, //标识通信端口的句柄

LPDCB lpDCB //指向一个设备节制块(DCB布局)的指针

);

DCB布局包孕了串口的各项参数设置,如下:

typedef strUCt _DCB

{

// dcb

DWORD DCBlength; // sizeof(DCB)

DWORD BaudRate; // current baud rate

DWORD fBinary: 1; // binary mode, no EOF check

DWORD fParity: 1; // enable parity checking

DWORD fOutxCtsFlow: 1; // CTS output flow control

DWORD fOutxDsrFlow: 1; // DSR output flow control

DWORD fDtrControl: 2; // DTR flow control type

DWORD fDsrSensitivity: 1; // DSR sensitivity

DWORD fTXContinueOnXoff: 1; // XOFF continues Tx

DWORD fOutX: 1; // XON/XOFF out flow control

DWORD fInX: 1; // XON/XOFF in flow control

DWORD fErrorChar: 1; // enable error replacement

DWORD fNull: 1; // enable null stripping

DWORD fRtsControl: 2; // RTS flow control

DWORD fAbortOnError: 1; // abort reads/writes on error

DWORD fDummy2: 17; // reserved

WORD wReserved; // not currently used

WORD XonLim; // transmit XON threshold

WORD XoffLim; // transmit XOFF threshold

BYTE ByteSize; // number of bits/byte, 4-8

BYTE Parity; // 0-4=no,odd,even,mark,space

BYTE StopBits; // 0,1,2 = 1, 1.5, 2

char XonChar; // Tx and Rx XON character

char XoffChar; // Tx and Rx XOFF character

char ErrorChar; // error replacement character

char EofChar; // end of input character

char EvtChar; // received event character

WORD wReserved1; // reserved; do not use

} DCB;

读写串口

在读写串口之前,还要用PurgeComm()函数清空缓冲区,并用SetCommMask ()函数设置事故掩模来监视指定通信端口上的事故,其原型为:

BOOL SetCommMask(

HANDLE hFile, //标识通信端口的句柄

DWORD dwEvtMask //能够使能的通信事故

);

串口上可能发生的事故如下表所示:

值 事故描述 EV_BREAK A break was detected on input. EV_CTS The CTS (clear-to-send) signal changed state. EV_DSR The DSR(data-set-ready) signal changed state. EV_ERR A line-status error occurred. Line-status errors are CE_FRAME, CE_OVERRUN, and CE_RXPARITY. EV_RING A ring indicator was detected. EV_RLSD The RLSD (receive-line-signal-detect) signal changed state. EV_RXCHAR A character was received and placed in the input buffer. EV_RXFLAG The event character was received and placed in the input buffer. The event character is specified in the device's DCB structure, which is applied to a serial port by using the SetCommState function. EV_TXEMPTY The last character in the output buffer was sent.

在设置好事故掩模后,我们就可以使用WaitCommEvent()函数来等待串口上发肇事故,其函数原型为:

BOOL WaitCommEvent(

HANDLE hFile, //标识通信端口的句柄

LPDWORD lpEvtMask, //指向寄放事故标识变量的指针

LPOVERLAPPED lpOverlapped, // 指向overlapped布局

);

我们可以在发肇事故后,根据响应的事故类型,进行串口的读写操作:

BOOL ReadFile(HANDLE hFile, //标识通信端口的句柄

LPVOID lpBuffer, //输入数据Buffer指针

DWORD nNumberOfBytesToRead, // 必要读取的字节数

LPDWORD lpNumberOfBytesRead, //实际读取的字节数指针

LPOVERLAPPED lpOverlapped //指向overlapped布局

);

BOOL WriteFile(HANDLE hFile, //标识通信端口的句柄

LPCVOID lpBuffer, //输出数据Buffer指针

DWORD nNumberOfBytesToWrite, //必要写的字节数

LPDWORD lpNumberOfBytesWritten, //实际写入的字节数指针

LPOVERLAPPED lpOverlapped //指向overlapped布局

);

2.工程实例

下面我们用第1节所述API实现一个多线程的串口通信法度榜样。这个例子工程(工程名为MultiThreadCom)的界面很简单,如下图所示:

它是一个多线程的利用法度榜样,包括两个事情者线程,分手处置惩罚串口1和串口2。为了简化问题,我们让连接两个串口的电缆只包孕RX、TX两根连线(即不以硬件节制RS-232,串口上只会发生EV_TXEMPTY、EV_RXCHAR事故)。

在工程实例的BOOL CMultiThreadComApp::InitInstance()函数中,启动并设置COM1和COM2,其源代码为:

BOOL CMultiThreadComApp::InitInstance()

{

AfxEnableControlContainer();

//打开并设置COM1

hComm1=CreateFile("COM1", GENERIC_READGENERIC_WRITE, 0, NULL ,OPEN_EXISTING, 0,NULL);

if (hComm1==(HANDLE)-1)

{

AfxMessageBox("打开COM1掉败");

return false;

}

else

{

DCB wdcb;

GetCommState (hComm1,&wdcb);

wdcb.BaudRate=9600;

SetCommState (hComm1,&wdcb);

PurgeComm(hComm1,PURGE_TXCLEAR);

}

//打开并设置COM2

hComm2=CreateFile("COM2", GENERIC_READGENERIC_WRITE, 0, NULL ,OPEN_EXISTING, 0,NULL);

if (hComm2==(HANDLE)-1)

{

AfxMessageBox("打开COM2掉败");

return false;

}

else

{

DCB wdcb;

GetCommState (hComm2,&wdcb);

wdcb.BaudRate=9600;

SetCommState (hComm2,&wdcb);

PurgeComm(hComm2,PURGE_TXCLEAR);

}

CMultiThreadComDlg dlg;

m_pMainWnd = &dlg;

int nResponse = dlg.DoModal();

if (nResponse == IDOK)

{

// TODO: Place code here to handle when the dialog is

// dismissed with OK

}

else if (nResponse == IDCANCEL)

{

// TODO: Place code here to handle when the dialog is

// dismissed with Cancel

}

return FALSE;

}

此后我们在对话框CMultiThreadComDlg的初始化函数OnInitDialog中启动两个分手处置惩罚COM1和COM2的线程:

BOOL CMultiThreadComDlg::OnInitDialog()

{

CDialog::OnInitDialog();

// Add "About..." menu item to system menu.

// IDM_ABOUTBOX must be in the system command range.

ASSERT((IDM_ABOUTBOX & 0xFFF0) == IDM_ABOUTBOX);

ASSERT(IDM_ABOUTBOX AppendMenu(MF_SEPARATOR);

pSysMenu->AppendMenu(MF_STRING, IDM_ABOUTBOX, strAboutMenu);

}

}

// Set the icon for this dialog. The framework does this automatically

// when the application's main window is not a dialog

SetIcon(m_hIcon, TRUE); // Set big icon

SetIcon(m_hIcon, FALSE); // Set small icon

// TODO: Add extra initialization here

//启动串口1处置惩罚线程

DWORD nThreadId1;

hCommThread1 = ::CreateThread((LPSECURITY_ATTRIBUTES)NULL, 0,

(LPTHREAD_START_ROUTINE)Com1ThreadPRocess, AfxGetMainWnd()->m_hWnd, 0, &nThreadId1);

if (hCommThread1 == NULL)

{

AfxMessageBox("创建串口1处置惩罚线程掉败");

return false;

}

//启动串口2处置惩罚线程

DWORD nThreadId2;

hCommThread2 = ::CreateThread((LPSECURITY_ATTRIBUTES)NULL, 0,

(LPTHREAD_START_ROUTINE)Com2ThreadProcess, AfxGetMainWnd()->m_hWnd, 0, &nThreadId2);

if (hCommThread2 == NULL)

{

AfxMessageBox("创建串口2处置惩罚线程掉败");

return false;

}

return TRUE; // return TRUE unless you set the focus to a control

}

两个串口COM1和COM2对应的线程处置惩罚函数等待串口上发肇事故,并根据事故类型和自身缓冲区是否稀有据要发送进行响应的处置惩罚,其源代码为:

DWORD WINAPI Com1ThreadProcess(HWND hWnd//主窗口句柄)

{

DWORD wEven;

char str[10]; //读入数据

SetCommMask(hComm1, EV_RXCHAR EV_TXEMPTY);

while (TRUE)

{

WaitCommEvent(hComm1, &wEven, NULL);

if(wEven = 0)

{

CloseHandle(hCommThread1);

hCommThread1 = NULL;

ExitThread(0);

}

else

{

switch (wEven)

{

case EV_TXEMPTY:

if (wTxPos0 && 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;

}

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