1 #include <stdio.h>
2 #include <stdlib.h>
3 #include <windows.h>
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NULL
114 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 port
129 &m_ov, // Overlapped structure
130 &BytesRead, // Stores number of bytes read
131 TRUE); // Wait flag
132 }
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 buffer
145 bResult = WriteFile(hComm, // Handle to COMM Port, 串口的句柄
146 m_szWriteBuffer, // Pointer to message buffer in calling finction
147 // 即以该指针的值为首地址的nNumberOfBytesToWrite
148 // 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 sent
151 // 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 structure
153 // 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NULL
155 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 port
171 &m_ov, // Overlapped structure
172 &BytesSent, // Stores number of bytes sent
173 TRUE); // Wait flag
174
175 // deal with the error code
176 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 send
182 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 }
