serialport.cpp

本例是一个关于串口通信的例子

/*
**	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 "SerialPort.h"

#include <assert.h>
#include ".\serialport.h"


//----------------------------------构造函数----------------------------------------
CSerialPort::CSerialPort()
{
	//串口句柄
	m_hComm = NULL; 
	//初始化结构体overlapped
	m_ov.Offset = 0;
	m_ov.OffsetHigh = 0;
	m_ov.hEvent = NULL;   
	//写事件
	m_hWriteEvent = NULL;
	//关闭事件
	m_hShutdownEvent = NULL;
	//写缓冲区
	m_szWriteBuffer = NULL;
    //线程状态 
	m_bThreadAlive = FALSE;
	//写大小
	m_nWriteSize = 0;
}


//----------------------------删除动态创建的内存-----------------------------------
CSerialPort::~CSerialPort()
{
	do
	{
		SetEvent(m_hShutdownEvent);
	} while (m_bThreadAlive);

	TRACE("结束线程\n");

	delete [] m_szWriteBuffer;
}


//-----------------------初始化端口，这个端口可以是1---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 < 11);
	assert(pPortOwner != NULL);

	// if the thread is alive: Kill
	if (m_bThreadAlive)
	{
		do
		{
			SetEvent(m_hShutdownEvent);
		} while (m_bThreadAlive);
		TRACE("结束线程\n");
	}

	//创建事件
	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);              //写串口事件

	if(m_hWriteCompleteEvent != NULL)
		ResetEvent(m_hWriteCompleteEvent);
	m_hWriteCompleteEvent = CreateEvent(NULL, TRUE, FALSE, NULL);      //写串口完成事件
	
	if (m_hShutdownEvent != NULL)
		ResetEvent(m_hShutdownEvent);
	m_hShutdownEvent = CreateEvent(NULL, TRUE, FALSE, NULL);           //关闭串口事件

	//初始化事件对象
	m_hEventArray[0] = m_hShutdownEvent;	//最高权限
	m_hEventArray[1] = m_ov.hEvent;
	m_hEventArray[2] = m_hWriteEvent;

	//初始化关键代码段
	InitializeCriticalSection(&m_csCommunicationSync);
	
	// set buffersize for writing and save the owner
	m_pOwnerWnd = pPortOwner;

	if (m_szWriteBuffer != NULL)
		delete [] m_szWriteBuffer;
	m_szWriteBuffer = new char[writebuffersize];

	//端口号 
	m_nPortNr = portnr;

	//写缓冲区大小
	m_nWriteBufferSize = writebuffersize;
	m_dwCommEvents = dwCommEvents;

	BOOL bResult = FALSE;
	char *szPort = new char[50];
	char *szBaud = new char[50];

	//-----------------------------进入关键代码段
	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;
	}

	//超时设置
	m_CommTimeouts.ReadIntervalTimeout = 1000;
	m_CommTimeouts.ReadTotalTimeoutMultiplier = 1000;
	m_CommTimeouts.ReadTotalTimeoutConstant = 1000;
	m_CommTimeouts.WriteTotalTimeoutMultiplier = 1000;
	m_CommTimeouts.WriteTotalTimeoutConstant = 1000;

	//配置
	if (SetCommTimeouts(m_hComm, &m_CommTimeouts))
	{						   
		if (SetCommMask(m_hComm, dwCommEvents))
		{
			if (GetCommState(m_hComm, &m_dcb))
			{
				m_dcb.fDtrControl = DTR_CONTROL_ENABLE;
				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);

	//-----------------------------退出关键代码段
	LeaveCriticalSection(&m_csCommunicationSync);

	TRACE("初始化串口 %d 完成\n使用函数（Startmonitor）开始通信.\n", portnr);

	return TRUE;
}


//线程函数
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;
		
	//comstat.fXoffSent = 0;
	//comstat.fXoffHold = 0;
	comstat.fEof = 1;
	//开始启动时候清除串口缓冲区
	// check if the port is opened
	if (port->m_hComm)		
		PurgeComm(port->m_hComm, PURGE_RXCLEAR | PURGE_TXCLEAR | PURGE_RXABORT | PURGE_TXABORT);

	//开始死循环.只要线程状态有效，该循环一直运行.
	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_pOwnerWnd->m_hWnd, WM_COMM_CTS_DETECTED, (WPARAM) 0, (LPARAM) port->m_nPortNr);
				if (CommEvent & EV_RXFLAG)
					::SendMessage(port->m_pOwnerWnd->m_hWnd, WM_COMM_RXFLAG_DETECTED, (WPARAM) 0, (LPARAM) port->m_nPortNr);
				if (CommEvent & EV_BREAK)
					::SendMessage(port->m_pOwnerWnd->m_hWnd, WM_COMM_BREAK_DETECTED, (WPARAM) 0, (LPARAM) port->m_nPortNr);