c语言怎么实现串口通信

编程原理

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程序1为查询通信方式接口程序，为一典型的数据采集例程。其中bioscom()函数初始化COM1(此函数实际调用BIOS

INT

14H中断0号功能)。这样在程序中就避免了具体设置波特率因子等繁琐工作，只需直接访问发送/接收寄存器(3F8H)和线路状态寄存

如何用C语言控制计算机串口

基本方法是使用CreateFile来建立一个串口文件，然后用overlap的方式进行读写

#define SERAIL_PORT_BUF_MAX (1024*8)

typedef HRESULT (*PFN_CMD_PARSE_DATA)(HANDLE hParseApp, LPCSTR szRspCmd, int nCmdLen);

class CUsbSrvApp// : public CWinApp

{

public:

CUsbSrvApp();

~CUsbSrvApp();

BOOL OnSendData(const char *szBuf, int nLen);// 发送数据

int ComConnect(CString strPort); // 连接COM口

HANDLE OpenComPort(CString strPort, int nBaudRate, int nDataBits, int nStopBits, int nParity, int nFlowCtrlType); // 打开串口

void Close(); // 关闭串口

HANDLE m_hCom;

BOOL m_bConnected;

OVERLAPPED m_OverlappedRead;

OVERLAPPED m_OverlappedWrite;

CWinThread *m_pThread;

PFN_CMD_PARSE_DATA m_pRspCmdFunc; // 用来处理接受数据的CALLBACK

HANDLE m_hParseApp;

};

CUsbSrvApp::CUsbSrvApp()

{

// TODO: add construction code here,

// Place all significant initialization in InitInstance

m_bConnected = false;

m_hCom = NULL;

m_pRspCmdFunc = NULL;

}

CUsbSrvApp::~CUsbSrvApp()

{

}

//打开串口通信，并返回串口句柄

HANDLE CUsbSrvApp::OpenComPort(CString strPortName,

int nBaudRate,

int nDataBits,

int nStopBits,

int nParity,

int nFlowCtrlType)

{

DCB dcb;

COMMTIMEOUTS CommTimeOuts ;

COMMCONFIG ComConfig;

HANDLE hComPort;

CString strPort;

strPort.Format("\\\\.\\%s",strPortName); // COM口的文件名应该是 \\.\COMXX

//打开窗口其实就是创建一个文件

hComPort = CreateFile(strPort,

GENERIC_READ | GENERIC_WRITE,

FILE_SHARE_READ | FILE_SHARE_WRITE,

NULL,

OPEN_EXISTING,

FILE_ATTRIBUTE_NORMAL|FILE_FLAG_OVERLAPPED,

NULL);

if (INVALID_HANDLE_VALUE == hComPort)

return INVALID_HANDLE_VALUE;

// 设置一些COM口通讯参数和OVERLAP

CommTimeOuts.ReadIntervalTimeout = -1;

CommTimeOuts.ReadTotalTimeoutConstant = 0;

CommTimeOuts.ReadTotalTimeoutMultiplier = 0;

CommTimeOuts.WriteTotalTimeoutConstant = 0;

CommTimeOuts.WriteTotalTimeoutMultiplier = 0x1388;

SetCommTimeouts( m_hCom, CommTimeOuts ) ;

SetDefaultCommConfig(strPortName, ComConfig, sizeof(COMMCONFIG));

GetCommState(m_hCom, dcb ) ;

dcb.BaudRate = nBaudRate;

dcb.ByteSize = nDataBits;

dcb.StopBits = nStopBits;

dcb.fParity = (NOPARITY != nParity);

dcb.Parity = nParity;

//set the receive char

dcb.EvtChar = 0x0D;

switch(nFlowCtrlType)

{

case 0: //no flow control

break;

case 1://HARD_FLOW_CTRL:

dcb.fOutxCtsFlow = TRUE;

dcb.fOutxDsrFlow = TRUE;

dcb.fDtrControl = DTR_CONTROL_DISABLE;

dcb.fDsrSensitivity = TRUE;

dcb.fRtsControl = RTS_CONTROL_TOGGLE;

break;

case 2://SOFT_FLOW_CTRL:

dcb.fOutX = TRUE;

dcb.fInX = TRUE;

break;

}

BuildCommDCB(_T("baud=115200 parity=N data=8 stop=1"),dcb);

SetCommState(hComPort, dcb ) ;

SetCommMask(hComPort, 0);

SetCommMask(hComPort, EV_RXCHAR|EV_CTS|EV_DSR|EV_RLSD|EV_RING);

SetupComm( hComPort, SERAIL_PORT_BUF_MAX,SERAIL_PORT_BUF_MAX) ;

//clear read and write buffer

PurgeComm( hComPort, PURGE_TXABORT | PURGE_RXABORT | PURGE_TXCLEAR | PURGE_RXCLEAR );

return hComPort;

}

void CUsbSrvApp::Close()

{

if(m_bConnected)

{

m_bConnected = false;

CloseHandle(m_hCom);

m_hCom = NULL;

}

}

// 这个线程是监视串口数据，一旦有数据则读取并调用CALLBACK通知客户端

UINT ReceiveComData(LPVOID pParam)

{

CUsbSrvApp *pUsbSrv = (CUsbSrvApp *)pParam;

HANDLE hComPort = pUsbSrv-m_hCom;

DWORD dwEvtMask=0;

DWORD dwErrorFlags;

SetCommMask( hComPort, EV_RXCHAR);

OVERLAPPED osRead;

osRead.hEvent = CreateEvent(NULL,FALSE,FALSE,NULL);

DWORD dwTransfer = 0;

while(pUsbSrv-m_bConnected)

{

if( !WaitCommEvent( hComPort, dwEvtMask,osRead))

{

if( GetLastError()== ERROR_IO_PENDING)

{

WaitForSingleObject(osRead.hEvent, INFINITE);

if(dwEvtMaskEV_RXCHAR==EV_RXCHAR)

{

COMSTAT ComStat={0} ;

DWORD dwReadLen = 0;

DWORD dwBytesRead = 0;

DWORD dwTotalLen = 0;

ClearCommError(hComPort, dwErrorFlags, ComStat );

dwTotalLen = ComStat.cbInQue;

dwReadLen = (SERAIL_PORT_BUF_MAX dwTotalLen)?dwTotalLen:SERAIL_PORT_BUF_MAX;

BYTE *pBuf = new BYTE[dwTotalLen+1];

memset(pBuf, 0 , dwTotalLen+1);

DWORD nReadBufLen=0;

while(dwTotalLen0)

{

if(FALSE == ReadFile( hComPort, pBuf+nReadBufLen,dwReadLen, dwBytesRead,pUsbSrv-m_OverlappedRead))

{

if(GetLastError() == ERROR_IO_PENDING)

{

GetOverlappedResult(hComPort,osRead, dwTransfer, TRUE );

}

break;

}

nReadBufLen +=dwBytesRead;

dwTotalLen -=dwBytesRead;

dwReadLen -= dwBytesRead;

dwReadLen = (SERAIL_PORT_BUF_MAXdwReadLen)?dwReadLen:SERAIL_PORT_BUF_MAX;

}

if(pUsbSrv-m_pRspCmdFunc!=NULLnReadBufLen!=0)

{

pUsbSrv-m_pRspCmdFunc(pUsbSrv-m_hParseApp, (char*)pBuf,nReadBufLen);

}

delete pBuf;

ClearCommError(hComPort, dwErrorFlags, ComStat );

int len =0;//= m_retList.GetSize();

}//endif if(dwEvtMaskEV_RXCHAR==EV_RXCHAR)

}//endif if( GetLastError()== ERROR_IO_PENDING)

}//endif if( !WaitCommEvent( hComPort, dwEvtMask,o))

else

{

if(GetLastError() == ERROR_IO_PENDING) {

GetOverlappedResult(hComPort, osRead, dwTransfer, TRUE ); // sleep thread

}

}

Sleep(1);

} //endwhile while(m_bConnected)

return 0;

}

int CUsbSrvApp::ComConnect(CString strPort)

{

int nBaudRate = 115200;

int nDataBits = 8;

int nStopBits = 1;

int nParity = 0;

int nFlowCtrl = 1;

if (NULL != m_hCom || m_bConnected)

{

return 0;

}

m_hCom = OpenComPort(strPort,nBaudRate,nDataBits,nStopBits,nParity,nFlowCtrl);

if( INVALID_HANDLE_VALUE == m_hCom)

{

m_hCom = NULL;

return 0;

}

memset( m_OverlappedRead, 0, sizeof( OVERLAPPED ) );

memset( m_OverlappedWrite, 0, sizeof( OVERLAPPED ) );

m_OverlappedRead.hEvent = CreateEvent( NULL, TRUE, FALSE, NULL );

m_OverlappedWrite.hEvent = CreateEvent( NULL, TRUE, FALSE, NULL );

m_pThread = AfxBeginThread( ReceiveComData,(void*)this,THREAD_PRIORITY_NORMAL,0,CREATE_SUSPENDED ,NULL );

if( NULL == m_pThread )

{

CloseHandle( m_hCom );

m_hCom = NULL;

return FALSE;

}

else

{

m_bConnected = TRUE;

m_pThread-ResumeThread( );

}

return TRUE;

}

int CUsbSrvApp::OnSendData(const char *szBuf, int nLen)

{

BOOL bWriteStat;

BOOL bWrite = TRUE;

DWORD dwBytesWrite = 0;

DWORD dwBytesWritten = 0;

int dwByteswrittenTotal = 0;

if (NULL == m_hCom)

return 0;

int nSentTimes=0;

while(dwByteswrittenTotalnLennSentTimes10)

{

nSentTimes++;

dwBytesWrite = nLen-dwByteswrittenTotal;

bWriteStat = WriteFile( m_hCom, szBuf+dwByteswrittenTotal, dwBytesWrite, dwBytesWritten, m_OverlappedWrite );

if( !bWriteStat)

{

if ( GetLastError() == ERROR_IO_PENDING )

{

dwBytesWritten = 0;

bWrite = FALSE;

}

}

if (!bWrite)

{

bWrite = TRUE;

bWriteStat = GetOverlappedResult(m_hCom, // Handle to COMM port

m_OverlappedWrite, // Overlapped structure

dwBytesWritten, // Stores number of bytes sent

TRUE); // Wait flag

//deal with the error code

}

dwByteswrittenTotal += dwBytesWritten;

}

if(dwByteswrittenTotalnLen)

return 0;

else

return 1;

}

VS或者VC6.0编写的C语言程序，怎样能够实现串口数据的收发?

1  、Windows   API通信函数方法 。与通信有关的Windows   API函数共有26个，但主要有关的有： CreateFile()   用   “comn”（n为串口号）作为文件名就可以打开串口。 ReadFile()   读串口。

2、WriteFile()   写串口。 CloseHandle()   关闭串口句柄。初始化时应注意CreateFile()函数中串口共享方式应设为0，串口为不可共享设备，其它与一般文件读写类似。以下给出API实现的源代码。

3、利用端口函数直接操作 。这种方式主要是采用两个端口函数_inp(),   _outp()实现对串口的读写，其中读端口函数的原型为： int   _inp(unsigned   shot   port) 。该函数从端口读取一个字节，端口号为0~65535。 写端口的函数原型为： nt   _outp(unsigned   shot   port,   int   databyte) 。

4、  MSComm控件 。MSComm控件是微软开发的专用通信控件，封装了串口的所有功能，使用很方便，但在实际应用中要小心对其属性进行配置。下面详细说明该类应用方法。 

串行端口的本质功能是作为CPU和串行设备间的编码转换器。当数据从 CPU经过串行端口发送出去时，字节数据转换为串行的位。在接收数据时，串行的位被转换为字节数据。

在Windows环境（Windows NT、Win98、Windows2000）下，串口是系统资源的一部分。

应用程序要使用串口进行通信，必须在使用之前向操作系统提出资源申请要求（打开串口），通信完成后必须释放资源（关闭串口）。

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