串口通信

這裏採用字符串池實現串口數據接收，串口類改自一個老外寫的CSerialPort類。

/*
**	FILENAME			CSerialPort.h
**
**	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 "stringpool.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:
	// contruction and destruction
	CSerialPort();
	virtual		~CSerialPort();

	// port initialisation											
	BOOL		InitPort(CWinThread* pPortOwner, UINT portnr = 1, UINT baud = 19200, char parity = 'N', UINT databits = 8, UINT stopsbits = 1, DWORD dwCommEvents = EV_RXCHAR | EV_CTS, UINT nBufferSize = 512);

	// start/stop comm watching
	BOOL		StartMonitoring();
	BOOL		RestartMonitoring();
	BOOL		StopMonitoring();

	DWORD		GetWriteBufferSize();
	DWORD		GetCommEvents();
	DCB			GetDCB();
	std::string *GetFrontString();

	void		WriteToPort(char* string);

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;
	CRITICAL_SECTION m_csQueLock;		//隊列鎖
	BOOL				m_bThreadAlive;

	//事件對象
	HANDLE				m_hShutdownEvent;
	HANDLE				m_hComm;
	HANDLE				m_hWriteEvent;
	HANDLE				m_hEventArray[3];
	
	// structures
	OVERLAPPED			m_ov;
	COMMTIMEOUTS		m_CommTimeouts;
	DCB					m_dcb;

public:
	CWinThread*				m_pOwner;
	StringPool *m_pStringPool;
	// misc
	UINT				m_nPortNr;
	char*				m_szWriteBuffer;
	DWORD				m_dwCommEvents;
	DWORD				m_nWriteBufferSize;
	UINT				m_nDataLen;
	queue<string *> m_strQue;			//字符串接收隊列
};

#endif __SERIALPORT_H__

/*
**	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>

//
// 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;
}

//
// 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(CWinThread* pPortOwner,	// the owner (CWinTread) of the port (receives message)
						   UINT  portnr,		//端口號
						   UINT  baud,			//波特率
						   char  parity,		//奇偶校驗位
						   UINT  databits,		//數據位 
						   UINT  stopbits,		// 停止位
						   DWORD dwCommEvents,	// 準備監視的串口事件掩碼
						   UINT  writebuffersize)	// 寫緩衝區大小
{
	assert(portnr > 0 && portnr < 5);
	assert(pPortOwner != NULL);

	//判斷線程是否啓動，否則結束線程
	if (m_bThreadAlive)
	{
		do
		{
			SetEvent(m_hShutdownEvent);
		} while (m_bThreadAlive);
		TRACE("Thread ended\n");
	}

	//重疊事件對象
	if (m_ov.hEvent != NULL)
		ResetEvent(m_ov.hEvent);
	m_ov.hEvent = CreateEvent(NULL, TRUE, FALSE, NULL);
	
	//寫事件對象
	if (m_hWriteEvent != NULL)
		ResetEvent(m_hWriteEvent);
	m_hWriteEvent = CreateEvent(NULL, TRUE, FALSE, NULL);

	//線程退出事件對象，有信號則線程退出
	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;

	InitializeCriticalSection(&m_csCommunicationSync);
	InitializeCriticalSection(&m_csQueLock);

	// set buffersize for writing and save the owner
	m_pOwner = pPortOwner;
	m_pStringPool = new StringPool;

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

	m_nPortNr = portnr;

	m_nWriteBufferSize = writebuffersize;
	m_dwCommEvents = dwCommEvents;
	m_nDataLen = 15;

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

	//鎖住串口，防止對同一串口進行操作
	EnterCriticalSection(&m_csCommunicationSync);

	if (m_hComm != NULL)
	{
		CloseHandle(m_hComm);
		m_hComm = NULL;
	}

	//串口連接字符串
	sprintf(szPort, "COM%d", portnr);
	sprintf(szBaud, "baud=%d parity=%c data=%d stop=%d", baud, parity, databits, stopbits);

	//打開串口
	m_hComm = CreateFileA(szPort,						//串口號
					     GENERIC_READ | GENERIC_WRITE,	// 允許讀寫
					     0,								// 以獨佔模式打開
					     NULL,							// 無安全屬性
					     OPEN_EXISTING,					// 通訊設備已存在
					     FILE_FLAG_OVERLAPPED,			// 異步IO
					     0);							//通訊設備不能用模板打開

	if (m_hComm == INVALID_HANDLE_VALUE)
	{
		// 串口未找到
		delete [] szPort;
		delete [] szBaud;

		return FALSE;
	}

	// 設置超時值
	m_CommTimeouts.ReadIntervalTimeout = 1000;
	m_CommTimeouts.ReadTotalTimeoutMultiplier = 1000;
	m_CommTimeouts.ReadTotalTimeoutConstant = 1000;
	m_CommTimeouts.WriteTotalTimeoutMultiplier = 1000;
	m_CommTimeouts.WriteTotalTimeoutConstant = 1000;

	if (SetCommTimeouts(m_hComm, &m_CommTimeouts))
	{		
		//設置串口要監視的事件
		if (SetCommMask(m_hComm, dwCommEvents))
		{
			//讀取串口配置
			if (GetCommState(m_hComm, &m_dcb))
			{
				m_dcb.fRtsControl = RTS_CONTROL_ENABLE;		// set RTS bit high!
				//連接串口
				if (BuildCommDCBA(szBaud, &m_dcb))
				{
					//修改串口配置
					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;

	// 清空緩衝區
	PurgeComm(m_hComm, PURGE_RXCLEAR | PURGE_TXCLEAR | PURGE_RXABORT | PURGE_TXABORT);

	LeaveCriticalSection(&m_csCommunicationSync);

	TRACE("Initialisation for communicationport %d completed.\nUse Startmonitor to communicate.\n", portnr);

	return TRUE;
}

UINT CSerialPort::CommThread(LPVOID pParam)
{
	CSerialPort *port = (CSerialPort*)pParam;
	
	//串口線程運行標誌
	port->m_bThreadAlive = TRUE;	
		
	DWORD BytesTransfered = 0; 
	DWORD Event = 0;
	DWORD CommEvent = 0;
	DWORD dwError = 0;
	COMSTAT comstat;
	BOOL  bResult = TRUE;
		
	//檢查串口是否打開
	if (port->m_hComm)		
		PurgeComm(port->m_hComm, PURGE_RXCLEAR | PURGE_TXCLEAR | PURGE_RXABORT | PURGE_TXABORT);

	//初始化COMSTAT
	ClearCommError(port->m_hComm, &dwError, &comstat);
	for (;;) 
	{ 
		//等待串口事件發生，異步操作直接返回
		bResult = WaitCommEvent(port->m_hComm, &Event, &port->m_ov);

		if (!bResult)  
		{ 
			//錯誤處理
			switch (dwError = GetLastError()) 
			{ 
			case ERROR_IO_PENDING: 	
				{ 
					break;
				}
			case 87:
				{
					//特殊處理
					break;
				}
			default:
				{
					port->ProcessErrorMessage("WaitCommEvent()");
					break;
				}
			}
		}
		//正常處理
		else
		{
			//清除串口的通信錯誤，返回當前的錯誤狀態
			bResult = ClearCommError(port->m_hComm, &dwError, &comstat);
			
			//串口未發送數據
			if (comstat.cbInQue == 0)
				continue;
		}
	
		//等待串口事件發生
		Event = WaitForMultipleObjects(3, port->m_hEventArray, FALSE, INFINITE);

		switch (Event)
		{
		case 0:
			{
				//0號事件對象擁有高優先權，會優先到達
			 	port->m_bThreadAlive = FALSE;

				//線程直接退出
				AfxEndThread(100);
				break;
			}
		case 1:	// 讀事件
			{
				//讀取串口事件掩碼
				GetCommMask(port->m_hComm, &CommEvent);

				if (CommEvent & EV_CTS)//CTS信號狀態發生變化
					::PostThreadMessage(port->m_pOwner->m_nThreadID, WM_COMM_CTS_DETECTED, (WPARAM) 0, (LPARAM) port->m_nPortNr);
				if (CommEvent & EV_RXFLAG)//接收到事件字符，並置於輸入緩衝區中 
					::PostThreadMessage(port->m_pOwner->m_nThreadID, WM_COMM_RXFLAG_DETECTED, (WPARAM) 0, (LPARAM) port->m_nPortNr);
				if (CommEvent & EV_BREAK) //輸入中發生中斷
					::PostThreadMessage(port->m_pOwner->m_nThreadID, WM_COMM_BREAK_DETECTED, (WPARAM) 0, (LPARAM) port->m_nPortNr);
				if (CommEvent & EV_ERR)//發生線路狀態錯誤，線路狀態錯誤包括CE_FRAME,CE_OVERRUN和CE_RXPARITY 
					::PostThreadMessage(port->m_pOwner->m_nThreadID, WM_COMM_ERR_DETECTED, (WPARAM) 0, (LPARAM) port->m_nPortNr);
				if (CommEvent & EV_RING)//檢測到振鈴指示
					::PostThreadMessage(port->m_pOwner->m_nThreadID, WM_COMM_RING_DETECTED, (WPARAM) 0, (LPARAM) port->m_nPortNr);
				
				if (CommEvent & EV_RXCHAR)
					//接收到字符，並置於輸入緩衝區中 
					ReceiveChar(port, comstat);
					
				break;
			}  
		case 2: // 寫事件
			{
				WriteChar(port);
				break;
			}
		}
	}

	return 0;
}

BOOL CSerialPort::StartMonitoring()
{
	if (!(m_Thread = AfxBeginThread(CommThread, this)))
		return FALSE;
	TRACE("Thread started\n");
	return TRUE;	
}

//喚醒線程
BOOL CSerialPort::RestartMonitoring()
{
	TRACE("Thread resumed\n");
	m_Thread->ResumeThread();
	return TRUE;	
}


//線程掛起
BOOL CSerialPort::StopMonitoring()
{
	TRACE("Thread suspended\n");
	m_Thread->SuspendThread(); 
	return TRUE;	
}


//查找詳細錯誤信息
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); 
	MessageBoxA(NULL, Temp, "Application Error", MB_ICONSTOP);

	LocalFree(lpMsgBuf);
	delete[] Temp;
}

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,			
							port->m_szWriteBuffer,					// 發送緩衝區首地址
							strlen((char*)port->m_szWriteBuffer),	// 消息發送長度
							&BytesSent,								// 實際寫入字節數的存儲區域指針
							&port->m_ov);				

		// 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,		// 發送字節數
									  TRUE); 			// 等待標誌

		LeaveCriticalSection(&port->m_csCommunicationSync);

		// deal with the error code 
		if (!bResult)  
		{
			port->ProcessErrorMessage("GetOverlappedResults() in WriteFile()");
		}	
	}

	//驗證是否是期望發送長度
	if (BytesSent != strlen((char*)port->m_szWriteBuffer))
	{
		TRACE("WARNING: WriteFile() error.. Bytes Sent: %d; Message Length: %d\n", BytesSent, strlen((char*)port->m_szWriteBuffer));
	}
}

void CSerialPort::ReceiveChar(CSerialPort* port, COMSTAT comstat)
{
	BOOL  bRead = TRUE; 
	BOOL  bResult = TRUE;
	DWORD dwError = 0;
	DWORD BytesRead = 0;
	unsigned char RXBuff[1024];
	int nRecvChar = 1;

	memset(RXBuff, 0, 1024);
	for (;;) 
	{ 
		//獲得串口權限
		EnterCriticalSection(&port->m_csCommunicationSync);
		
		////清除串口的通信錯誤返回當前串口狀態
		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)
		{	
			//接收緩衝區爲空直接退出
			break;
		}
						
		EnterCriticalSection(&port->m_csCommunicationSync);

		//讀緩衝區
		if (bRead)
		{
			bResult = ReadFile(port->m_hComm,		// 串口句柄
							   &RXBuff,							// 讀緩衝區地址
							   nRecvChar,						// 要讀取的長度
							   &BytesRead,						// 讀取長度
							   &port->m_ov);

			//正常返回值爲FALSE，調用GetOverlappedResult獲取重疊結果
			if (!bResult)  
			{ 
				switch (dwError = GetLastError()) 
				{ 
					case ERROR_IO_PENDING: 	
						{ 
							bRead = FALSE;
							break;
						}
					default:
						{
							port->ProcessErrorMessage("ReadFile()");
							break;
						} 
				}
			}
			else
			{
				//讀取操作完成，不需要調用GetOverlappedResult
				bRead = TRUE;
			}
		}
		//獲取異步結果
		if (!bRead)
		{
			//重置bRead
			bRead = TRUE;
			bResult = GetOverlappedResult(port->m_hComm,
										  &port->m_ov,	
										  &BytesRead,	//返回讀取的長度
										  TRUE); 			// 等待標誌
			if (!bResult)  
			{
				port->ProcessErrorMessage("GetOverlappedResults() in ReadFile()");
			}
		}

		if (bRead)
		{
			if (RXBuff[0] == '#')
			{
				nRecvChar = port->m_nDataLen;
				continue;
			}
			if (strlen((char*)&RXBuff[0]) < port->m_nDataLen)
			{
				nRecvChar = 1;
				continue;
			}
			std::string *pStrMsg = (port->m_pStringPool)->GetAString();
			pStrMsg->assign((char *)&RXBuff[0], BytesRead);
			if (pStrMsg->find('#') != std::string::npos)
			{
				nRecvChar = 1;
				(port->m_pStringPool)->ReleaseAString(pStrMsg);
				continue;
			}
			nRecvChar = 1;
			//將字符串放入接收隊列
			EnterCriticalSection(&port->m_csQueLock);
			port->m_strQue.push(pStrMsg);
			LeaveCriticalSection(&port->m_csQueLock);
		}
				
		LeaveCriticalSection(&port->m_csCommunicationSync);
		
		::PostThreadMessage((port->m_pOwner)->m_nThreadID, WM_COMM_RXCHAR, (WPARAM) port, (LPARAM) port->m_nPortNr);
	}

}

void CSerialPort::WriteToPort(char* string)
{		
	assert(m_hComm != 0);

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

	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;
}

std::string *CSerialPort::GetFrontString()
{
	EnterCriticalSection(&m_csQueLock);
	if (!m_strQue.empty())
	{
		string *pString = m_strQue.front();
		m_strQue.pop();
		LeaveCriticalSection(&m_csQueLock);
		return pString;
	}
	else
	{
		LeaveCriticalSection(&m_csQueLock);
		return NULL;
	}
}