CSerialPort类源代码分析
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前几篇串口编程大致讲述了Windows下串口的大致操作，接下来分析流行的SerialPort类，它把Windows API封装好，方便开发利用
1、Win32下串口大致操作流程
(1)打开串口：CreateFile函数
(2)建立串口通信事件:CreateEvent函数
(3)初始化串口:SetCommState函数
(4)建立监视线程,即读写数据线程,因为我们不知道什么时候数据会到来,这里是一个异步事件
(5)写数据:WriteFile
(6)结束:关闭线程->停止WaitCommEvent->CloseHandle
2.SerialPort类的数据结构
大致了解操作流程后,先看一下SerialPort类,均在代码注释了
数据成员:
01.public: 02. int m_nWriteSize; //要写入串口的数据大小 03. HANDLE m_hComm; //串口句柄 04.protected: 05. // thread监视线程 06. CWinThread* m_Thread; 07. 08. // synchronisation objects 09. //临界资源 10. CRITICAL_SECTION m_csCommunicationSync; 11. //监视线程运行标志 12. BOOL m_bThreadAlive; 13. 14. // handles 15. /*事件句柄*/ 16. HANDLE m_hWriteEvent; 17. HANDLE m_hShutdownEvent; 18. 19. // There is a general shutdown when the port is closed. 20. //事件数组，包括一个写事件，接收事件，关闭事件 21. HANDLE m_hEventArray[3]; 22. 23. // structures 24. OVERLAPPED m_ov; //异步I/O模型 25. COMMTIMEOUTS m_CommTimeouts; //超时设置 26. DCB m_dcb; //设备控制块 27. 28. // owner window 29. CWnd* m_pOwner; 30. 31. // misc 32. UINT m_nPortNr; 33. char* m_szWriteBuffer; //写缓冲区 34. DWORD m_dwCommEvents; // 35. DWORD m_nWriteBufferSize; //写缓冲大小
函数成员：
01.public: 02. /*******************Port Operation***********************/ 03. 04. // port initialisation 05. /*初始化串口*/ 06. BOOL InitPort(CWnd* pPortOwner, 07. UINT portnr = 1, 08. UINT baud = 19200, 09. char parity = 'N', 10. UINT databits = 8, 11. UINT stopbits = 1, 12. DWORD dwCommEvents = EV_RXCHAR, 13. UINT writebuffersize = 1024); 14. //关闭端口 15. void ClosePort(); 16. // start/stop comm watching 17. //控制串口监视线程 18. BOOL StartMonitoring(); //开启 19. BOOL RestartMonitoring(); //复位 20. BOOL StopMonitoring(); //停止 21. 22. DWORD GetWriteBufferSize();//获取写缓冲大小 23. DWORD GetCommEvents(); //获取事件 24. DCB GetDCB(); //获取DCB 25. //写数据到串口 26. void WriteToPort(char* string); 27. void WriteToPort(char* string,int n); 28. void WriteToPort(LPCTSTR string); 29. void WriteToPort(LPCTSTR string,int n); 30.protected: 31./***************** protected memberfunctions **********************/ 32. void ProcessErrorMessage(char* ErrorText); 33. //线程函数 34. static UINT CommThread(LPVOID pParam); 35. //接收字符 36. static void ReceiveChar(CSerialPort* port, COMSTAT comstat); 37. //写字符 38. static void WriteChar(CSerialPort* port);
3.串口操作
(1)初始化串口
流程：检查参数-->检测线程-->创建事件(监视线程)-->打开端口-->设置异步IO结构参数,详细见代码:
01./*初始化串口*/ 02.BOOL CSerialPort::InitPort(CWnd* pPortOwner, // the owner (CWnd) of the port (receives message) 03. UINT portnr, // portnumber (1..4) 04. UINT baud, // baudrate 05. char parity, // parity 06. UINT databits, // databits 07. UINT stopbits, // stopbits 08. DWORD dwCommEvents, // EV_RXCHAR, EV_CTS etc 09. UINT writebuffersize) // size to the writebuffer 10.{ 11. assert(portnr > 0 && portnr < 5); 12. assert(pPortOwner != NULL); 13. 14. // if the thread is alive: Kill 15. //线程在的话关断它 16. if (m_bThreadAlive) 17. { 18. do 19. { 20. SetEvent(m_hShutdownEvent); 21. } while (m_bThreadAlive); 22. TRACE("Thread ended/n"); 23. } 24. 25. // create events 26. //创建事件 27. if (m_ov.hEvent != NULL) 28. ResetEvent(m_ov.hEvent); 29. else 30. m_ov.hEvent = CreateEvent(NULL, TRUE, FALSE, NULL); 31. 32. if (m_hWriteEvent != NULL) 33. ResetEvent(m_hWriteEvent); 34. else 35. m_hWriteEvent = CreateEvent(NULL, TRUE, FALSE, NULL); 36. 37. if (m_hShutdownEvent != NULL) 38. ResetEvent(m_hShutdownEvent); 39. else 40. m_hShutdownEvent = CreateEvent(NULL, TRUE, FALSE, NULL); 41. 42. // initialize the event objects 43. //事件数组初始化，设定优先级别 44. m_hEventArray[0] = m_hShutdownEvent; // highest priority 45. m_hEventArray[1] = m_ov.hEvent; 46. m_hEventArray[2] = m_hWriteEvent; 47. 48. // initialize critical section 49. //初始化一个临界资源对象 50. InitializeCriticalSection(&m_csCommunicationSync); 51. 52. // set buffersize for writing and save the owner 53. m_pOwner = pPortOwner; 54. 55. if (m_szWriteBuffer != NULL) 56. delete [] m_szWriteBuffer; 57. m_szWriteBuffer = new char[writebuffersize]; 58. 59. m_nPortNr = portnr; 60. 61. m_nWriteBufferSize = writebuffersize; 62. m_dwCommEvents = dwCommEvents; 63. 64. BOOL bResult = FALSE; 65. char *szPort = new char[50]; 66. char *szBaud = new char[50]; 67. 68. // now it critical! 69. /********************************************* 70. 多个线程操作相同的数据时，一般是需要按顺序访问的，否则会引导数据错乱， 71. 无法控制数据，变成随机变量。为解决这个问题，就需要引入互斥变量，让每个 72. 线程都按顺序地访问变量。这样就需要使用EnterCriticalSection和LeaveCriticalSection函数。 73. **********************************************************************/ 74. //进入临界区 75. EnterCriticalSection(&m_csCommunicationSync); 76. 77. // if the port is already opened: close it 78. //端口已经打开的就关闭它 79. if (m_hComm != NULL) 80. { 81. CloseHandle(m_hComm); 82. m_hComm = NULL; 83. } 84. 85. // prepare port strings 86. //串口参数 87. sprintf(szPort, "COM%d", portnr); 88. sprintf(szBaud, "baud=%d parity=%c data=%d stop=%d", baud, parity, databits, stopbits); 89. 90. // get a handle to the port 91. /**************************************************************** 92. *通信程序在CreateFile处指定串口设备及相关的操作属性，再返回一个句柄， 93. *该句柄将被用于后续的通信操作，并贯穿整个通信过程串口打开后，其属性 94. *被设置为默认值，根据具体需要，通过调用GetCommState(hComm,&&dcb)读取 95. *当前串口设备控制块DCB设置，修改后通过SetCommState(hComm,&&dcb)将其写 96. *入。运用ReadFile()与WriteFile()这两个API函数实现串口读写操作，若为异 97. *步通信方式，两函数中最后一个参数为指向OVERLAPPED结构的非空指针，在读 98. *写函数返回值为FALSE的情况下，调用GetLastError()函数，返回值为ERROR_IO_PENDING， 99. *表明I/O操作悬挂，即操作转入后台继续执行。此时，可以用WaitForSingleObject() 100. *来等待结束信号并设置最长等待时间 101. *****************************************************************/ 102. m_hComm = CreateFile(szPort, // communication port string (COMX)串口号 103. GENERIC_READ | GENERIC_WRITE, // read/write types 可以读写 104. 0, // comm devices must be opened with exclusive access独占方式打开串口 105. NULL, // no security attributes 无安全属性 106. OPEN_EXISTING, // comm devices must use OPEN_EXISTING 107. FILE_FLAG_OVERLAPPED, // Async I/O 异步I/O 108. 0); // template must be 0 for comm devices 109. 110. //如果创建不成功，错误处理 111. if (m_hComm == INVALID_HANDLE_VALUE) 112. { 113. // port not found 114. delete [] szPort; 115. delete [] szBaud; 116. 117. return FALSE; 118. } 119. 120. // set the timeout values 121. //设置超时上限(异步IO) 122. m_CommTimeouts.ReadIntervalTimeout = 1000; 123. m_CommTimeouts.ReadTotalTimeoutMultiplier = 1000; 124. m_CommTimeouts.ReadTotalTimeoutConstant = 1000; 125. m_CommTimeouts.WriteTotalTimeoutMultiplier = 1000; 126. m_CommTimeouts.WriteTotalTimeoutConstant = 1000; 127. 128. // configure 129. /*分别调用Windows API设置串口参数*/ 130. if (SetCommTimeouts(m_hComm, &m_CommTimeouts)) //设置超时 131. { 132. /******************************************************* 133. 若对端口数据的响应时间要求较严格，可采用事件驱动方式。 134. 事件驱动方式通过设置事件通知，当所希望的事件发生时，Windows 135. 发出该事件已发生的通知，这与DOS环境下的中断方式很相似。Windows 136. 定义了9种串口通信事件，较常用的有以下三种： 137. 138. EV_RXCHAR:接收到一个字节，并放入输入缓冲区； 139. 140. EV_TXEMPTY:输出缓冲区中的最后一个字符，发送出去； 141. 142. EV_RXFLAG:接收到事件字符(DCB结构中EvtChar成员)，放入输入缓冲区 143. 144. 在用SetCommMask()指定了有用的事件后，应用程序可调用WaitCommEvent()来等待事 145. 件的发生。SetCommMask(hComm,0)可使WaitCommEvent()中止。 146. **************************************************************/ 147. if (SetCommMask(m_hComm, dwCommEvents)) //设置通信事件 148. { 149. if (GetCommState(m_hComm, &m_dcb)) //获取当前DCB参数 150. { 151. m_dcb.EvtChar = 'q'; //设置字件字符 152. m_dcb.fRtsControl = RTS_CONTROL_ENABLE; // set RTS bit high! 153. if (BuildCommDCB(szBaud, &m_dcb)) //填写DCB结构 154. { 155. if (SetCommState(m_hComm, &m_dcb)) //配置DCB 156. ; // normal operation... continue 157. else 158. ProcessErrorMessage("SetCommState()"); 159. } 160. else 161. ProcessErrorMessage("BuildCommDCB()"); 162. } 163. else 164. ProcessErrorMessage("GetCommState()"); 165. } 166. else 167. ProcessErrorMessage("SetCommMask()"); 168. } 169. else 170. ProcessErrorMessage("SetCommTimeouts()"); 171. 172. delete [] szPort; 173. delete [] szBaud; 174. 175. // flush the port 176. //终止读写并清空接收和发送 177. PurgeComm(m_hComm, PURGE_RXCLEAR | PURGE_TXCLEAR | PURGE_RXABORT | PURGE_TXABORT); 178. 179. // release critical section 180. //出临界区 181. LeaveCriticalSection(&m_csCommunicationSync); 182. 183. TRACE("Initialisation for communicationport %d completed./nUse Startmonitor to communicate./n", portnr); 184. 185. return TRUE; 186.}
(2)监视线程的控制
先看比较简单的线程控制吧，主要有开启线程，复位和停止
01.//开始监视串口 02.BOOL CSerialPort::StartMonitoring() 03.{ 04. if (!(m_Thread = AfxBeginThread(CommThread, this))) 05. return FALSE; 06. TRACE("Thread started/n"); 07. return TRUE; 08.} 09. 10.// 11.// Restart the comm thread 12.// 13.//重启监视线程（挂起重启） 14.BOOL CSerialPort::RestartMonitoring() 15.{ 16. TRACE("Thread resumed/n"); 17. m_Thread->ResumeThread(); 18. return TRUE; 19.} 20. 21. 22.// 23.// Suspend the comm thread 24.// 25.//挂起监视线程 26.BOOL CSerialPort::StopMonitoring() 27.{ 28. TRACE("Thread suspended/n"); 29. m_Thread->SuspendThread(); 30. return TRUE; 31.}
(3)监视线程
我们把读写串口的操作全部交给监视线程，现在简单看一下监视线程的大致流程：
检查串口-->进入循环{WaitCommEvent(不阻塞询问)询问事件-->如果有事件来到-->到相应处理(关闭/读/写)}
详细代码如下:
01.//监视串口函数 02.UINT CSerialPort::CommThread(LPVOID pParam) 03.{ 04. // Cast the void pointer passed to the thread back to 05. // a pointer of CSerialPort class 06. CSerialPort *port = (CSerialPort*)pParam; 07. 08. // Set the status variable in the dialog class to 09. // TRUE to indicate the thread is running. 10. port->m_bThreadAlive = TRUE; 11. 12. // Misc. variables 13. DWORD BytesTransfered = 0; 14. DWORD Event = 0; 15. DWORD CommEvent = 0; 16. DWORD dwError = 0; 17. COMSTAT comstat; 18. BOOL bResult = TRUE; 19. 20. // Clear comm buffers at startup 21. //检查串口是否打开 22. if (port->m_hComm) // check if the port is opened 23. PurgeComm(port->m_hComm, PURGE_RXCLEAR | PURGE_TXCLEAR | PURGE_RXABORT | PURGE_TXABORT); 24. 25. // begin forever loop. This loop will run as long as the thread is alive. 26. //不断读取数据 27. for (;;) 28. { 29. 30. // Make a call to WaitCommEvent(). This call will return immediatly 31. // because our port was created as an async port (FILE_FLAG_OVERLAPPED 32. // and an m_OverlappedStructerlapped structure specified). This call will cause the 33. // m_OverlappedStructerlapped element m_OverlappedStruct.hEvent, which is part of the m_hEventArray to 34. // be placed in a non-signeled state if there are no bytes available to be read, 35. // or to a signeled state if there are bytes available. If this event handle 36. // is set to the non-signeled state, it will be set to signeled when a 37. // character arrives at the port. 38. 39. // we do this for each port! 40. /******************************************************************** 41. WaitCommEvent函数第3个参数1pOverlapped可以是一个OVERLAPPED结构的变量指针 42. ，也可以是NULL，当用NULL时，表示该函数是同步的，否则表示该函数是异步的。 43. 调用WaitCommEvent时，如果异步操作不能立即完成，会立即返回FALSE，系统在 44. WaitCommEvent返回前将OVERLAPPED结构成员hEvent设为无信号状态，等到产生通信 45. 事件时，系统将其置有信号 46. ***********************************************************************/ 47. bResult = WaitCommEvent(port->m_hComm, &Event, &port->m_ov);//表示该函数是异步的 48. 49. 50. if (!bResult) 51. { 52. //如果WaitCommEvent返回Error为NULL，则查询错误信息 53. // If WaitCommEvent() returns FALSE, process the last error to determin 54. // the reason.. 55. switch (dwError = GetLastError()) 56. { 57. case ERROR_IO_PENDING: //正常情况，没有字符可读 58. { 59. // This is a normal return value if there are no bytes 60. // to read at the port. 61. // Do nothing and continue 62. break; 63. } 64. case 87: //系统错误 65. { 66. // Under Windows NT, this value is returned for some reason. 67. // I have not investigated why, but it is also a valid reply 68. // Also do nothing and continue. 69. break; 70. } 71. default: //发生其他错误 72. { 73. // All other error codes indicate a serious error has 74. // occured. Process this error. 75. port->ProcessErrorMessage("WaitCommEvent()"); 76. break; 77. } 78. } 79. } 80. else //WaitCommEvent()能正确返回 81. { 82. // If WaitCommEvent() returns TRUE, check to be sure there are 83. // actually bytes in the buffer to read. 84. // 85. // If you are reading more than one byte at a time from the buffer 86. // (which this program does not do) you will have the situation occur 87. // where the first byte to arrive will cause the WaitForMultipleObjects() 88. // function to stop waiting. The WaitForMultipleObjects() function 89. // resets the event handle in m_OverlappedStruct.hEvent to the non-signelead state 90. // as it returns. 91. // 92. // If in the time between the reset of this event and the call to 93. // ReadFile() more bytes arrive, the m_OverlappedStruct.hEvent handle will be set again 94. // to the signeled state. When the call to ReadFile() occurs, it will 95. // read all of the bytes from the buffer, and the program will 96. // loop back around to WaitCommEvent(). 97. // 98. // At this point you will be in the situation where m_OverlappedStruct.hEvent is set, 99. // but there are no bytes available to read. If you proceed and call 100. // ReadFile(), it will return immediatly due to the async port setup, but 101. // GetOverlappedResults() will not return until the next character arrives. 102. // 103. // It is not desirable for the GetOverlappedResults() function to be in 104. // this state. The thread shutdown event (event 0) and the WriteFile() 105. // event (Event2) will not work if the thread is blocked by GetOverlappedResults(). 106. // 107. // The solution to this is to check the buffer with a call to ClearCommError(). 108. // This call will reset the event handle, and if there are no bytes to read 109. // we can loop back through WaitCommEvent() again, then proceed. 110. // If there are really bytes to read, do nothing and proceed. 111. 112. bResult = ClearCommError(port->m_hComm, &dwError, &comstat); 113. 114. if (comstat.cbInQue == 0) 115. continue; 116. } // end if bResult 117. 118. //主等待函数，会阻塞线程 119. // Main wait function. This function will normally block the thread 120. // until one of nine events occur that require action. 121. //等待3个事件：关断/读/写，有一个事件发生就返回 122. Event = WaitForMultipleObjects(3, //3个事件 123. port->m_hEventArray,//事件数组 124. FALSE, //有一个事件发生就返回 125. INFINITE); //超时时间 126. 127. switch (Event) 128. { 129. case 0: 130. { 131. // Shutdown event. This is event zero so it will be 132. // the higest priority and be serviced first. 133. //关断事件，关闭串口 134. CloseHandle(port->m_hComm); 135. port->m_hComm=NULL; 136. port->m_bThreadAlive = FALSE; 137. 138. // Kill this thread. break is not needed, but makes me feel better. 139. AfxEndThread(100); 140. 141. break; 142. } 143. case 1: // read event 将定义的各种消息发送出去 144. { 145. //接收 146. GetCommMask(port->m_hComm, &CommEvent); 147. if (CommEvent & EV_RXCHAR) 148. // Receive character event from port. 149. ReceiveChar(port, comstat); 150. if (CommEvent & EV_CTS) 151. ::SendMessage(port->m_pOwner->m_hWnd, WM_COMM_CTS_DETECTED, (WPARAM) 0, (LPARAM) port->m_nPortNr); 152. if (CommEvent & EV_BREAK) 153. ::SendMessage(port->m_pOwner->m_hWnd, WM_COMM_BREAK_DETECTED, (WPARAM) 0, (LPARAM) port->m_nPortNr); 154. if (CommEvent & EV_ERR) 155. ::SendMessage(port->m_pOwner->m_hWnd, WM_COMM_ERR_DETECTED, (WPARAM) 0, (LPARAM) port->m_nPortNr); 156. if (CommEvent & EV_RING) 157. ::SendMessage(port->m_pOwner->m_hWnd, WM_COMM_RING_DETECTED, (WPARAM) 0, (LPARAM) port->m_nPortNr); 158. 159. if (CommEvent & EV_RXFLAG) 160. ::SendMessage(port->m_pOwner->m_hWnd, WM_COMM_RXFLAG_DETECTED, (WPARAM) 0, (LPARAM) port->m_nPortNr); 161. 162. break; 163. } 164. case 2: // write event发送数据 165. { 166. // Write character event from port 167. //写 168. WriteChar(port); 169. break; 170. } 171. 172. } // end switch 173. 174. } // close forever loop 175. 176. return 0; 177.}
(4)读取数据操作
读取数据是一个异步操作，当有数据发来时，会触发读事件m_ov.hEvent，监视线程捕捉到事件后并获知是读事件，进入相关读处理，这里调用函数ReceiveChar，ReceiveChar中调用ReadFile函数将串口数据读到Buffer缓冲中，相关代码如下：
01.//接收数据 02.void CSerialPort::ReceiveChar(CSerialPort* port, COMSTAT comstat) 03.{ 04. BOOL bRead = TRUE; 05. BOOL bResult = TRUE; 06. DWORD dwError = 0; 07. DWORD BytesRead = 0; 08. unsigned char RXBuff; 09. 10. for (;;) 11. { 12. // Gain ownership of the comm port critical section. 13. // This process guarantees no other part of this program 14. // is using the port object. 15. 16. EnterCriticalSection(&port->m_csCommunicationSync); 17. 18. // ClearCommError() will update the COMSTAT structure and 19. // clear any other errors. 20. //更新COMSTAT 21. bResult = ClearCommError(port->m_hComm, &dwError, &comstat); 22. 23. LeaveCriticalSection(&port->m_csCommunicationSync); 24. 25. // start forever loop. I use this type of loop because I 26. // do not know at runtime how many loops this will have to 27. // run. My solution is to start a forever loop and to 28. // break out of it when I have processed all of the 29. // data available. Be careful with this approach and 30. // be sure your loop will exit. 31. // My reasons for this are not as clear in this sample 32. // as it is in my production code, but I have found this 33. // solutiion to be the most efficient way to do this. 34. //所有字符均被读出，中断循环 35. if (comstat.cbInQue == 0) 36. { 37. // break out when all bytes have been read 38. break; 39. } 40. 41. EnterCriticalSection(&port->m_csCommunicationSync); 42. 43. if (bRead) 44. { 45. //串口读出，读出缓冲区中字节 46. bResult = ReadFile(port->m_hComm, // Handle to COMM port 47. &RXBuff, // RX Buffer Pointer 48. 1, // Read one byte 49. &BytesRead, // Stores number of bytes read 50. &port->m_ov); // pointer to the m_ov structure 51. // deal with the error code 52. //若返回错误，错误处理 53. if (!bResult) 54. { 55. switch (dwError = GetLastError()) 56. { 57. case ERROR_IO_PENDING: 58. { 59. // asynchronous i/o is still in progress 60. // Proceed on to GetOverlappedResults(); 61. //异步IO仍在进行 62. bRead = FALSE; 63. break; 64. } 65. default: 66. { //其他错误处理 67. // Another error has occured. Process this error. 68. port->ProcessErrorMessage("ReadFile()"); 69. break; 70. } 71. } 72. } 73. else 74. { //ReadFile返回TRUE 75. // ReadFile() returned complete. It is not necessary to call GetOverlappedResults() 76. bRead = TRUE; 77. } 78. } // close if (bRead) 79. //异步IO操作仍在进行，需要调用GetOverlappedResult查询 80. if (!bRead) 81. { 82. bRead = TRUE; 83. bResult = GetOverlappedResult(port->m_hComm, // Handle to COMM port 84. &port->m_ov, // Overlapped structure 85. &BytesRead, // Stores number of bytes read 86. TRUE); // Wait flag 87. 88. // deal with the error code 89. if (!bResult) 90. { 91. port->ProcessErrorMessage("GetOverlappedResults() in ReadFile()"); 92. } 93. } // close if (!bRead) 94. 95. LeaveCriticalSection(&port->m_csCommunicationSync); 96. 97. // notify parent that a byte was received 98. ::SendMessage((port->m_pOwner)->m_hWnd, WM_COMM_RXCHAR, (WPARAM) RXBuff, (LPARAM) port->m_nPortNr); 99. } // end forever loop 100. 101.}
(5)写数据
也是由监视线程操作，不过触发事件交给主线程来触发，函数是WriteToPort
01.// 02.// Write a string to the port 03.// 04.void CSerialPort::WriteToPort(char* string) 05.{ 06. assert(m_hComm != 0); 07. //写进写缓冲区 08. memset(m_szWriteBuffer, 0, sizeof(m_szWriteBuffer)); 09. strcpy(m_szWriteBuffer, string); 10. m_nWriteSize=strlen(string); 11. 12. // set event for write 13. SetEvent(m_hWriteEvent); 14.}
线程调用的函数WriteChar，把缓冲里的数据写到串口中，期间调用WriteFile 详细代码：
01.//写数据 02.void CSerialPort::WriteChar(CSerialPort* port) 03.{ 04. BOOL bWrite = TRUE; 05. BOOL bResult = TRUE; 06. 07. DWORD BytesSent = 0; 08. 09. ResetEvent(port->m_hWriteEvent); //复位写事件句柄 10. 11. // Gain ownership of the critical section 12. EnterCriticalSection(&port->m_csCommunicationSync); 13. 14. if (bWrite) 15. { 16. // Initailize variables 17. port->m_ov.Offset = 0; 18. port->m_ov.OffsetHigh = 0; 19. 20. // Clear buffer 21. PurgeComm(port->m_hComm, PURGE_RXCLEAR | PURGE_TXCLEAR | PURGE_RXABORT | PURGE_TXABORT); 22. 23. //串口写入 24. bResult = WriteFile(port->m_hComm, // Handle to COMM Port 25. port->m_szWriteBuffer, // Pointer to message buffer in calling finction 26.// strlen((char*)port->m_szWriteBuffer), // Length of message to send 27. port->m_nWriteSize, // Length of message to send 28. &BytesSent, // Where to store the number of bytes sent 29. &port->m_ov); // Overlapped structure 30. 31. // deal with any error codes 32. if (!bResult) 33. { 34. DWORD dwError = GetLastError(); 35. switch (dwError) 36. { 37. case ERROR_IO_PENDING: 38. { 39. // continue to GetOverlappedResults() 40. BytesSent = 0; 41. bWrite = FALSE; 42. break; 43. } 44. default: 45. { 46. // all other error codes 47. port->ProcessErrorMessage("WriteFile()"); 48. } 49. } 50. } 51. else 52. { 53. LeaveCriticalSection(&port->m_csCommunicationSync); 54. } 55. } // end if(bWrite) 56. 57. if (!bWrite) 58. { 59. bWrite = TRUE; 60. 61. bResult = GetOverlappedResult(port->m_hComm, // Handle to COMM port 62. &port->m_ov, // Overlapped structure 63. &BytesSent, // Stores number of bytes sent 64. TRUE); // Wait flag 65. 66. LeaveCriticalSection(&port->m_csCommunicationSync); 67. 68. // deal with the error code 69.// if (!bResult) 70. { 71.// port->ProcessErrorMessage("GetOverlappedResults() in WriteFile()"); 72. } 73. } // end if (!bWrite) 74. 75. //Verify that the data size send equals what we tried to send 76. if (BytesSent != port->m_nWriteSize) // Length of message to send) 77. { 78. TRACE("WARNING: WriteFile() error.. Bytes Sent: %d; Message Length: %d/n", BytesSent, strlen((char*)port->m_szWriteBuffer)); 79. } 80.// ::SendMessage((port->m_pOwner)->m_hWnd, WM_COMM_TXEMPTY_DETECTED, (WPARAM) RXBuff, (LPARAM) port->m_nPortNr); 81.// ::SendMessage((port->m_pOwner)->m_hWnd, WM_COMM_TXEMPTY_DETECTED,0,(LPARAM) port->m_nPortNr); 82.}
(6)其他操作
其他比如获取DCB，关闭等，比较简单，不做分析 代码如下：
01.// 02.// Return the device control block 03.// 04.DCB CSerialPort::GetDCB() 05.{ 06. return m_dcb; 07.} 08. 09.// 10.// Return the communication event masks 11.// 12.DWORD CSerialPort::GetCommEvents() 13.{ 14. return m_dwCommEvents; 15.} 16. 17.// 18.// Return the output buffer size 19.// 20.DWORD CSerialPort::GetWriteBufferSize() 21.{ 22. return m_nWriteBufferSize; 23.} 24. 25. 26.void CSerialPort::ClosePort() 27.{ 28. SetEvent(m_hShutdownEvent); 29.}
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