1 #include 
       
          2 #include 
        
           3 #include 
         
            4   5 HANDLE hComm;  6 OVERLAPPED m_ov;  7 COMSTAT comstat;  8 DWORD    m_dwCommEvents;  9  10 //如果在调用CreateFile创建句柄时指 11 //定了FILE_FLAG_OVERLAPPED标志，那么调用ReadFile和WriteFile对该句柄进 12 //行的操作就应该是重叠的；如果未指定 13 //重叠标志，则读写操作应该是同步的 14 //在同步执行时，函数直到操作完成后才返回。这意味着同步执行时线程会被阻塞，从 15 //而导致效率下降。在重叠执行时，即使操作还未完成，这两个函数也会立即返回，费 16 //时的I/O操作在后台进行 17 bool openport(char *portname)//打开一个串口 18 { 19     hComm = CreateFile(portname, 20         GENERIC_READ | GENERIC_WRITE, 21         0, 22         0, 23         OPEN_EXISTING, 24         FILE_FLAG_OVERLAPPED,     25         0); 26     if (hComm == INVALID_HANDLE_VALUE) 27         return FALSE; 28     else 29         return true; 30 } 31  32  33 bool setupdcb(int rate_arg) 34 { 35     DCB  dcb; 36     int rate= rate_arg; 37     memset(&dcb,0,sizeof(dcb)); //在一段内存块中填充某个给定的值，是对较大的结构//体或数组进行清零操作的一种最快方法 38     if(!GetCommState(hComm,&dcb))//获取当前DCB配置 39     { 40         return FALSE; 41     } 42     /* -------------------------------------------------------------------- */ 43     // set DCB to configure the serial port 44     dcb.DCBlength       = sizeof(dcb); 45     /* ---------- Serial Port Config ------- */ 46     dcb.BaudRate        = rate; 47     dcb.Parity      = NOPARITY; 48     dcb.fParity     = 0; 49     dcb.StopBits        = ONESTOPBIT; 50     dcb.ByteSize        = 8; 51     dcb.fOutxCtsFlow    = 0; 52     dcb.fOutxDsrFlow    = 0; 53     dcb.fDtrControl     = DTR_CONTROL_DISABLE; 54     dcb.fDsrSensitivity = 0; 55     dcb.fRtsControl     = RTS_CONTROL_DISABLE; 56     dcb.fOutX           = 0; 57     dcb.fInX            = 0; 58     /* ----------------- misc parameters ----- */ 59     dcb.fErrorChar      = 0; 60     dcb.fBinary         = 1; 61     dcb.fNull           = 0; 62     dcb.fAbortOnError   = 0; 63     dcb.wReserved       = 0; 64     dcb.XonLim          = 2; 65     dcb.XoffLim         = 4; 66     dcb.XonChar         = 0x13; 67     dcb.XoffChar        = 0x19; 68     dcb.EvtChar         = 0; 69     /* -------------------------------------------------------------------- */ 70     // set DCB 71     if(!SetCommState(hComm,&dcb)) 72     { 73         return false; 74     } 75     else 76         return true; 77 } 78 //在用readfile和writefile读写串行口时，需要考虑超时问题, 读写串口的超时有两 79 //种：间隔超时和总超时, 写操作只支持总超时，而读操作两种超时均支持, 如果所有 80 //写超时参数均为0，那么就不使用写超时。 81 bool setuptimeout(DWORD ReadInterval,DWORD ReadTotalMultiplier,DWORD ReadTotalconstant,DWORD WriteTotalMultiplier,DWORD WriteTotalconstant)                82 { 83     COMMTIMEOUTS timeouts; 84     timeouts.ReadIntervalTimeout=ReadInterval; //读间隔超时 85     timeouts.ReadTotalTimeoutConstant=ReadTotalconstant; //读时间系数 86     timeouts.ReadTotalTimeoutMultiplier=ReadTotalMultiplier; //读时间常量 87     timeouts.WriteTotalTimeoutConstant=WriteTotalconstant; // 写时间系数 88     timeouts.WriteTotalTimeoutMultiplier=WriteTotalMultiplier; //写时间常//量, 总超时的计算公式是：总超时＝时间系数×要求读/写的字符数＋时间常量 89     if(!SetCommTimeouts(hComm, &timeouts)) 90     { 91         return false; 92     } 93     else 94         return true; 95 } 96 void ReceiveChar(){ 97     BOOL  bRead = TRUE; 98     BOOL  bResult = TRUE; 99     DWORD dwError = 0;100     DWORD BytesRead = 0;101     char RXBuff;102     while(true){103         bResult = ClearCommError(hComm, &dwError, &comstat);104         // 在使用ReadFile 函数进行读操作前，应先使用ClearCommError函数清除错误105         if(comstat.cbInQue==0)// COMSTAT结构返回串口状态信息106             //本文只用到了cbInQue成员变量，该成员变量的值代表输入缓冲区的字节数107             continue;108         if(bRead){109             bResult = ReadFile(hComm, // Handle to COMM port串口的句柄110                 &RXBuff,// RX Buffer Pointer// 读入的数据存储的地址，即读入的数据将存//储在以该指针的值为首地址的一片内存区111                 1,// Read one byte要读入的数据的字节数,112                 &BytesRead, // Stores number of bytes read, 指向一个DWORD//数值，该数值返回读操作实际读入的字节数113                 &m_ov);           // pointer to the m_ov structure// 重叠操作时，该参数指向一个OVERLAPPED结构，同步操作时，该参数为NULL114             printf("%c",RXBuff);115             if (!bResult){
     // 当ReadFile和WriteFile返回FALSE时，不一定就是操作失//败，线程应该调用GetLastError函数分析返回的结果116                 switch (dwError = GetLastError()){117                 case ERROR_IO_PENDING:118                         bRead = FALSE;119                         break;120                 default:break;121                 }122             }else{123                 bRead = TRUE;124             }125         }  // close if (bRead)126         if (!bRead){127             bRead = TRUE;128             bResult = GetOverlappedResult(hComm,    // Handle to COMM port129                 &m_ov,    // Overlapped structure130                 &BytesRead,        // Stores number of bytes read131                 TRUE);             // Wait flag132         }133     }134 }135 BOOL WriteChar(BYTE* m_szWriteBuffer,DWORD m_nToSend){136     BOOL bWrite = TRUE;137     BOOL bResult = TRUE;138     DWORD BytesSent = 0;139     HANDLE    m_hWriteEvent;140     ResetEvent(m_hWriteEvent);141     if (bWrite){142         m_ov.Offset = 0;143         m_ov.OffsetHigh = 0;144         // Clear buffer145         bResult = WriteFile(hComm,    // Handle to COMM Port, 串口的句柄146             m_szWriteBuffer,        // Pointer to message buffer in calling finction147                                     // 即以该指针的值为首地址的nNumberOfBytesToWrite148                                     // 个字节的数据将要写入串口的发送数据缓冲区149             m_nToSend,                // Length of message to send, 要写入的数据的字节数150             &BytesSent,                // Where to store the number of bytes sent151                                     // 指向指向一个DWORD数值，该数值返回实际写入的字节数152             &m_ov );                // Overlapped structure153                                     // 重叠操作时，该参数指向一个OVERLAPPED结构，154                                     // 同步操作时，该参数为NULL155         if (!bResult){                // 当ReadFile和WriteFile返回FALSE时，不一定就是操作失156             //败，线程应该调用GetLastError函数分析返回的结果157             DWORD dwError = GetLastError();158             switch (dwError){159             case ERROR_IO_PENDING: //GetLastError函数返回//ERROR_IO_PENDING。这说明重叠操作还未完成160                     // continue to GetOverlappedResults()161                     BytesSent = 0;162                     bWrite = FALSE;163                     break;164             default:break;165             }166         }167     } // end if(bWrite)168     if (!bWrite){169         bWrite = TRUE;170         bResult = GetOverlappedResult(hComm,    // Handle to COMM port171             &m_ov,        // Overlapped structure172             &BytesSent,        // Stores number of bytes sent173             TRUE);             // Wait flag174         175         // deal with the error code176         if (!bResult){177             printf("GetOverlappedResults() in WriteFile()");178         }179     } // end if (!bWrite)180     181     // Verify that the data size send equals what we tried to send182     if (BytesSent != m_nToSend){183         printf("WARNING: WriteFile() error.. Bytes Sent: %d; Message Length: %d\n", BytesSent, strlen((char*)m_szWriteBuffer));184     }185     return true;186 }187 188 189 void   main(){190     if(openport("com4"))191         printf("open comport success\n");192     if(setupdcb(115200))193         printf("setupDCB success\n");194     if(setuptimeout(0,0,0,0,0)) //如果所有写超时参数均为0，那么就不使用写超时195         printf("setuptimeout success\n");196     PurgeComm(hComm, PURGE_RXCLEAR | PURGE_TXCLEAR | PURGE_RXABORT | PURGE_TXABORT); // 在读写串口之前，还要用PurgeComm()函数清空缓冲区197     //PURGE_TXABORT      中断所有写操作并立即返回，即使写操作还没有完成。198     //PURGE_RXABORT      中断所有读操作并立即返回，即使读操作还没有完成。199     //PURGE_TXCLEAR      清除输出缓冲区200     //PURGE_RXCLEAR      清除输入缓冲区201     //WriteChar("please send data now",20);202     printf("received data:\n");203     ReceiveChar( );204     system("pause");205 }