ModBus协议
Modbus协议是一种标准的工业控制通讯协议，无论是串口通讯，以太网通讯还是CAN通讯，在数据层都可以使用Modbus协议封装数据帧，Modbus协议支持一对多通信，采用一问一答的方式保证了通讯数据的可靠性和安全性。
功能码0x03表示查询指令，0x06表示写单个寄存器指令，0x10表示写多个寄存器指令。通常情况下，这三个功能码就能满足大多数实际场合下的应用。
Modbus协议单个收发指令的字节数都是由程序员事先设计好的，所以当发送一条指令后，接收指令的字节长度是确定的，利用这个规则笔者设计了一个CSerialPort类来实现Modbus协议下的串口编程。
CSerialPort
首先，CSerialPort完成了如下功能，
1）InitPort()函数为打开串口，设定波特率，校验位，数据位，停止位信息
2）LaunchCommand()函数完成了指令发送和接收功能，该函数在接收代码部分设定了代码保护区CRITICAL_SECTION，防止多线程编程时串口缓冲区出现异常。
CSerialPort.h如下代码所示
#ifndef __SERIALPORT_H__
#define __SERIALPORT_H__
typedef struct
{
int type;
int len;
char buff[32];
int timeout;
int retry;
}LCFLAG;
#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(CWnd* pPortOwner, UINT portnr = 1, UINT baud = 57600, char parity = 'N', UINT databits = 8, UINT stopsbits = 1, UINT timeout=80,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();
void WriteToPort(char* string);
BOOL OpenPort(CWnd* pPortOwner, UINT portnr = 1, UINT baud = 57600, char parity = 'N', UINT databits = 8, UINT stopsbits = 1, UINT timeout = 80, DWORD dwCommEvents = EV_RXCHAR | EV_CTS, UINT nBufferSize = 512);
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_csIFSync;
BOOL m_bThreadAlive;
// handles
HANDLE m_hShutdownEvent;
HANDLE m_hComm;
HANDLE m_hWriteEvent;
HANDLE m_hRecvEvent;
// Event array.
// One element is used for each event. There are two event handles for each port.
// A Write event and a receive character event which is located in the overlapped structure (m_ov.hEvent).
// There is a general shutdown when the port is closed.
HANDLE m_hEventArray[3];
// structures
OVERLAPPED m_ov;
COMMTIMEOUTS m_CommTimeouts;
DCB m_dcb;
// owner window
CWnd* m_pOwner;
// misc
UINT m_nPortNr;
char m_szWriteBuffer[4096];
DWORD m_dwCommEvents;
DWORD m_nWriteBufferSize;
public:
int m_nBufferLen;
void WriteBin2Port(unsigned char* szBuffer, int nLen);
public:
void ClosePort(void);
BOOL ReConfigComPort(int nBaudrate, BYTE nDataBits, int nStopBits, int nParity, int nTimeOut);
void SetPortOwner(CWnd* pWnd);
int m_nPort;
int GetPort(void);
int LanuchCommand(unsigned char* cmd, int len, unsigned char* recbuff, LCFLAG *pFlag);
unsigned char m_pRecvBuff[1024];
int m_RecvLen;
};
#endif __SERIALPORT_H__
CSerialPort.cpp如下代码所示
/*
** 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.
*/
#include "stdafx.h"
#include "SerialPort.h"
#include <assert.h>
#include ".\serialport.h"
//
// Constructor
//
CSerialPort::CSerialPort()
: m_nBufferLen(0)
, m_nPort(0)
, m_RecvLen(0)
{
m_pOwner = NULL;
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_hRecvEvent = NULL;
// m_szWriteBuffer = NULL;
m_bThreadAlive = FALSE;
}
//
// Delete dynamic memory
//
CSerialPort::~CSerialPort()
{
do
{
SetEvent(m_hShutdownEvent);
} while (m_bThreadAlive);
TRACE("Thread ended\n");
if (m_hComm != NULL)
{
CloseHandle(m_hComm);
m_hComm = NULL;
}
// delete [] m_szWriteBuffer;
}
//
// Initialize the port. This can be port 1 to 255.
//
BOOL CSerialPort::InitPort(CWnd* pPortOwner, // the owner (CWnd) of the port (receives message)
UINT portnr, // portnumber
UINT baud, // baudrate
char parity, // parity
UINT databits, // databits
UINT stopbits, // stopbits
UINT timeout,
DWORD dwCommEvents, // EV_RXCHAR, EV_CTS etc
UINT writebuffersize) // size to the writebuffer
{
assert(portnr > 0 && portnr <= 255);
// assert(pPortOwner != NULL);
m_nPort=-1;
// if the thread is alive: Kill
if (m_bThreadAlive)
{
do
{
SetEvent(m_hShutdownEvent);
} while (m_bThreadAlive);
TRACE("Thread ended\n");
}
// create events
if (m_ov.hEvent != NULL)
ResetEvent(m_ov.hEvent);
m_ov.hEvent = CreateEvent(NULL, TRUE, FALSE, NULL);
if (m_hWriteEvent != NULL)
ResetEvent(m_hWriteEvent);
m_hWriteEvent = CreateEvent(NULL, TRUE, FALSE, NULL);
if (m_hRecvEvent != NULL)
ResetEvent(m_hRecvEvent);
m_hRecvEvent = CreateEvent(NULL, TRUE, FALSE, NULL);
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;
// initialize critical section
InitializeCriticalSection(&m_csCommunicationSync);
InitializeCriticalSection(&m_csIFSync);
// set buffersize for writing and save the owner
m_pOwner = pPortOwner;
// if (m_szWriteBuffer != NULL)
// delete [] m_szWriteBuffer;
//m_szWriteBuffer = new char[4096];//writebuffersize];
////////////////k
// memset(m_szWriteBuffer,0,sizeof(m_szWriteBuffer));
//////////////k
m_nPortNr = portnr;
m_nWriteBufferSize = 4096;//writebuffersize;
m_dwCommEvents = dwCommEvents;
BOOL bResult = FALSE;
char *szPort = new char[50];
char *szBaud = new char[50];
// now it critical!
EnterCriticalSection(&m_csCommunicationSync);
// if the port is already opened: close it
if (m_hComm != NULL)
{
CloseHandle(m_hComm);
m_hComm = NULL;
}
// prepare port strings
sprintf_s(szPort,50, "\\\\.\\COM%d", portnr);
sprintf_s(szBaud, 50,"baud=%d parity=%c data=%d stop=%d", baud, parity, databits, stopbits);
// get a handle to the port
m_hComm = CreateFile(szPort, // communication port string (COMX)
GENERIC_READ | GENERIC_WRITE, // read/write types
0, // comm devices must be opened with exclusive access
NULL, // no security attributes
OPEN_EXISTING, // comm devices must use OPEN_EXISTING
FILE_FLAG_OVERLAPPED, // Async I/O
0); // template must be 0 for comm devices
if (m_hComm == INVALID_HANDLE_VALUE)
{
// port not found
delete [] szPort;
delete [] szBaud;
return FALSE;
}
// set the timeout values
m_CommTimeouts.ReadIntervalTimeout =
m_CommTimeouts.ReadTotalTimeoutMultiplier =
m_CommTimeouts.ReadTotalTimeoutConstant =
m_CommTimeouts.WriteTotalTimeoutMultiplier =
m_CommTimeouts.WriteTotalTimeoutConstant = 80;
// configure
if (SetCommTimeouts(m_hComm, &m_CommTimeouts))
{
if (SetCommMask(m_hComm, dwCommEvents))
{
if (GetCommState(m_hComm, &m_dcb))
{
m_dcb.fRtsControl = RTS_CONTROL_ENABLE; // set RTS bit high!
m_dcb.fDtrControl = DTR_CONTROL_ENABLE; // set RTS bit high!
if (BuildCommDCB(szBaud, &m_dcb))
{
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;
// flush the port
PurgeComm(m_hComm, PURGE_RXCLEAR | PURGE_TXCLEAR | PURGE_RXABORT | PURGE_TXABORT);
// release critical section
LeaveCriticalSection(&m_csCommunicationSync);
TRACE("Initialisation for communication port %d completed.\nUse Startmonitor to communicate.\n", portnr);
m_nPort=portnr;
return TRUE;
}
//
// The CommThread Function.
//
UINT CSerialPort::CommThread(LPVOID pParam)
{
// Cast the void pointer passed to the thread back to
// a pointer of CSerialPort class
CSerialPort *port = (CSerialPort*)pParam;
// Set the status variable in the dialog class to
// TRUE to indicate the thread is running.
port->m_bThreadAlive = TRUE;
// Misc. variables
DWORD BytesTransfered = 0;
DWORD Event = 0;
DWORD CommEvent = 0;
DWORD dwError = 0;
COMSTAT comstat;
BOOL bResult = TRUE;
// Clear comm buffers at startup
if (port->m_hComm) // check if the port is opened
{
PurgeComm(port->m_hComm, PURGE_RXCLEAR | PURGE_TXCLEAR | PURGE_RXABORT | PURGE_TXABORT);
ClearCommError(port->m_hComm, &dwError, &comstat);
}
// begin forever loop. This loop will run as long as the thread is alive.
for (;;)
{
// Make a call to WaitCommEvent(). This call will return immediatly
// because our port was created as an async port (FILE_FLAG_OVERLAPPED
// and an m_OverlappedStructerlapped structure specified). This call will cause the
// m_OverlappedStructerlapped element m_OverlappedStruct.hEvent, which is part of the m_hEventArray to
// be placed in a non-signeled state if there are no bytes available to be read,
// or to a signeled state if there are bytes available. If this event handle
// is set to the non-signeled state, it will be set to signeled when a
// character arrives at the port.
// we do this for each port!
bResult = WaitCommEvent(port->m_hComm, &Event, &port->m_ov);
if (!bResult)
{
// If WaitCommEvent() returns FALSE, process the last error to determin
// the reason..
switch (dwError = GetLastError())
{
case ERROR_IO_PENDING:
{
// This is a normal return value if there are no bytes
// to read at the port.
// Do nothing and continue
break;
}
case 87:
{
// Under Windows NT, this value is returned for some reason.
// I have not investigated why, but it is also a valid reply
// Also do nothing and continue.
break;
}
default:
{
// All other error codes indicate a serious error has
// occured. Process this error.
port->ProcessErrorMessage("WaitCommEvent()");
break;
}
}
}
else
{
// If WaitCommEvent() returns TRUE, check to be sure there are
// actually bytes in the buffer to read.
//
// If you are reading more than one byte at a time from the buffer
// (which this program does not do) you will have the situation occur
// where the first byte to arrive will cause the WaitForMultipleObjects()
// function to stop waiting. The WaitForMultipleObjects() function
// resets the event handle in m_OverlappedStruct.hEvent to the non-signelead state
// as it returns.
//
// If in the time between the reset of this event and the call to
// ReadFile() more bytes arrive, the m_OverlappedStruct.hEvent handle will be set again
// to the signeled state. When the call to ReadFile() occurs, it will
// read all of the bytes from the buffer, and the program will
// loop back around to WaitCommEvent().
//
// At this point you will be in the situation where m_OverlappedStruct.hEvent is set,
// but there are no bytes available to read. If you proceed and call
// ReadFile(), it will return immediatly due to the async port setup, but
// GetOverlappedResults() will not return until the next character arrives.
//
// It is not desirable for the GetOverlappedResults() function to be in
// this state. The thread shutdown event (event 0) and the WriteFile()
// event (Event2) will not work if the thread is blocked by GetOverlappedResults().
//
// The solution to this is to check the buffer with a call to ClearCommError().
// This call will reset the event handle, and if there are no bytes to read
// we can loop back through WaitCommEvent() again, then proceed.
// If there are really bytes to read, do nothing and proceed.
bResult = ClearCommError(port->m_hComm, &dwError, &comstat);
if (comstat.cbInQue == 0)
continue;
} // end if bResult
// Main wait function. This function will normally block the thread
// until one of nine events occur that require action.
Event = WaitForMultipleObjects(3, port->m_hEventArray, FALSE, INFINITE);
switch (Event)
{
case 0:
{
// Shutdown event. This is event zero so it will be
// the higest priority and be serviced first.
port->m_bThreadAlive = FALSE;
// Kill this thread. break is not needed, but makes me feel better.
AfxEndThread(100);
break;
}
case 1: // read event
{
GetCommMask(port->m_hComm, &CommEvent);
//if (CommEvent & EV_CTS)
// ::SendMessage(port->m_pOwner->m_hWnd, WM_COMM_CTS_DETECTED, (WPARAM) 0, (LPARAM) port->m_nPortNr);
//if (CommEvent & EV_RXFLAG)
// ::SendMessage(port->m_pOwner->m_hWnd, WM_COMM_RXFLAG_DETECTED, (WPARAM) 0, (LPARAM) port->m_nPortNr);
//if (CommEvent & EV_BREAK)
// ::SendMessage(port->m_pOwner->m_hWnd, WM_COMM_BREAK_DETECTED, (WPARAM) 0, (LPARAM) port->m_nPortNr);
//if (CommEvent & EV_ERR)
// ::SendMessage(port->m_pOwner->m_hWnd, WM_COMM_ERR_DETECTED, (WPARAM) 0, (LPARAM) port->m_nPortNr);
//if (CommEvent & EV_RING)
// ::SendMessage(port->m_pOwner->m_hWnd, WM_COMM_RING_DETECTED, (WPARAM) 0, (LPARAM) port->m_nPortNr);
if (CommEvent & EV_RXCHAR)
// Receive character event from port.
ReceiveChar(port, comstat);
break;
}
case 2: // write event
{
// Write character event from port
WriteChar(port);
break;
}
} // end switch
} // close forever loop
return 0;
}
//
// start comm watching
//
BOOL CSerialPort::StartMonitoring()
{
if (!(m_Thread = AfxBeginThread((AFX_THREADPROC)CommThread, this,THREAD_PRIORITY_HIGHEST)))
return FALSE;
TRACE("Thread started\n");
return TRUE;
}
//
// Restart the comm thread
//
BOOL CSerialPort::RestartMonitoring()
{
TRACE("Thread resumed\n");
m_Thread->ResumeThread();
return TRUE;
}
//
// Suspend the comm thread
//
BOOL CSerialPort::StopMonitoring()
{
TRACE("Thread suspended\n");
m_Thread->SuspendThread();
return TRUE;
}
//
// If there is a error, give the right message
//
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_s(Temp,200, "WARNING: %s Failed with the following error: \n%s\nPort: %d\n", (char*)ErrorText, lpMsgBuf, m_nPortNr);
MessageBox(NULL, Temp, "Application Error", MB_ICONSTOP);
LocalFree(lpMsgBuf);
delete[] Temp;
}
//
// Write a character.
//
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, // Handle to COMM Port
port->m_szWriteBuffer, // Pointer to message buffer in calling finction
port->m_nWriteBufferSize,
// strlen((char*)port->m_szWriteBuffer), // Length of message to send
&BytesSent, // Where to store the number of bytes sent
&port->m_ov); // Overlapped structure
// 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, // Stores number of bytes sent
TRUE); // Wait flag
LeaveCriticalSection(&port->m_csCommunicationSync);
// deal with the error code
if (!bResult)
{
port->ProcessErrorMessage("GetOverlappedResults() in WriteFile()");
}
} // end if (!bWrite)
// Verify that the data size send equals what we tried to send
if (BytesSent != port->m_nWriteBufferSize)//strlen((char*)port->m_szWriteBuffer))
{
// CString str;
// str.Format("WARNING: WriteFile() error.. Bytes Sent: %d; Message Length: %d\n", BytesSent, strlen((char*)port->m_szWriteBuffer));
// AfxMessageBox(str);
}
// memset(port->m_szWriteBuffer,0,strlen((char*)port->m_szWriteBuffer));
// ::PostMessage((port->m_pOwner)->m_hWnd, WM_COMM_RXCHAR, (WPARAM) 1, (LPARAM) 0);
}
//
// Character received. Inform the owner
//
void CSerialPort::ReceiveChar(CSerialPort* port, COMSTAT comstat)
{
BOOL bRead = TRUE;
BOOL bResult = TRUE;
DWORD dwError = 0;
DWORD BytesRead = 0;
unsigned char RXBuff;
for (;;)
{
// Gain ownership of the comm port critical section.
// This process guarantees no other part of this program
// is using the port object.
EnterCriticalSection(&port->m_csCommunicationSync);
// ClearCommError() will update the COMSTAT structure and
// clear any other errors.
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)
{
// break out when all bytes have been read
break;
}
EnterCriticalSection(&port->m_csCommunicationSync);
if (bRead)
{
bResult = ReadFile(port->m_hComm, // Handle to COMM port
&RXBuff, // RX Buffer Pointer
1, // Read one byte
&BytesRead, // Stores number of bytes read
&port->m_ov); // pointer to the m_ov structure
// deal with the error code
if (!bResult)
{
switch (dwError = GetLastError())
{
case ERROR_IO_PENDING:
{
// asynchronous i/o is still in progress
// Proceed on to GetOverlappedResults();
bRead = FALSE;
break;
}
default:
{
// Another error has occured. Process this error.
port->ProcessErrorMessage("ReadFile()");
break;
}
}
}
else
{
// ReadFile() returned complete. It is not necessary to call GetOverlappedResults()
bRead = TRUE;
}
} // close if (bRead)
if (!bRead)
{
bRead = TRUE;
bResult = GetOverlappedResult(port->m_hComm, // Handle to COMM port
&port->m_ov, // Overlapped structure
&BytesRead, // Stores number of bytes read
TRUE); // Wait flag
// deal with the error code
if (!bResult)
{
port->ProcessErrorMessage("GetOverlappedResults() in ReadFile()");
}
} // close if (!bRead)
if (port->m_RecvLen<1024)
{
port->m_pRecvBuff[port->m_RecvLen++] = RXBuff;
//int len=port->
//port->m_pRecvBuff[(*(port->m_pRecvLen))++] = RXBuff;
SetEvent(port->m_hRecvEvent);
}
LeaveCriticalSection(&port->m_csCommunicationSync);
// notify parent that a byte was received
if(port->m_pOwner)
::PostMessage((port->m_pOwner)->m_hWnd, WM_COMM_RXCHAR, (WPARAM)RXBuff, (LPARAM)port->m_nPortNr);
} // end forever loop
}
//
// Write a string to the port
//
void CSerialPort::WriteToPort(char* string)
{
assert(m_hComm != 0);
// memset(m_szWriteBuffer, 0, sizeof(m_szWriteBuffer));
strcpy_s(m_szWriteBuffer,4096, string);
// strcat(m_szWriteBuffer, string);
m_nWriteBufferSize=(DWORD)strlen(string);
// set event for write
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;
}
void CSerialPort::WriteBin2Port(unsigned char* szBuffer, int nLen)
{
memcpy(m_szWriteBuffer,szBuffer,nLen);
m_nWriteBufferSize=nLen;
SetEvent(m_hWriteEvent);
}
void CSerialPort::ClosePort(void)
{
do
{
SetEvent(m_hShutdownEvent);
} while (m_bThreadAlive);
TRACE("Thread ended\n");
if (m_hComm != NULL)
{
CloseHandle(m_hComm);
m_hComm = NULL;
}
}
//
//BOOL CSerialPort::ReConfigComPort(int nBaudrate, BYTE nDataBits, int nStopBits, int nParity, int nTimeOut)
//{
//// COMMTIMEOUTS commTimeouts;
//// commTimeouts.ReadIntervalTimeout=
//// commTimeouts.ReadTotalTimeoutConstant=
//// commTimeouts.ReadTotalTimeoutMultiplier=
//// commTimeouts.WriteTotalTimeoutConstant=
//// commTimeouts.WriteTotalTimeoutMultiplier=nTimeOut;
////
//// /* switch(nBaudrate)
//// {
//// case 0:
//// m_dcb.BaudRate=CBR_1200;
//// break;
//// case 1:
//// m_dcb.BaudRate=CBR_2400;
//// break;
//// case 2:
//// m_dcb.BaudRate=CBR_4800;
//// break;
//// case 3:
//// m_dcb.BaudRate=CBR_9600;
//// break;
//// case 3:
//// m_dcb.BaudRate=CBR_9600;
//// break;
//// m_dcb.BaudRate
////*/
//// m_dcb.BaudRate=BAUDRATES[nBaudrate];
//// m_dcb.ByteSize=nDataBits;
/////* m_dcb.Parity=NOPARITY;
//// m_dcb.Parity=ODDPARITY;
//// m_dcb.Parity=EVENPARITY;
////*/
//// m_dcb.Parity=PARITY[nParity];
/////* m_dcb.StopBits=ONESTOPBIT;
//// m_dcb.StopBits=ONE5STOPBITS;
//// m_dcb.StopBits=TWOSTOPBITS;
////*/
//// m_dcb.StopBits=STOPBITS[nStopBits];
////
//// return SetCommTimeouts(m_hComm, &commTimeouts)&&SetCommState(m_hComm,&m_dcb);
////
// return 0;
//}
//
void CSerialPort::SetPortOwner(CWnd* pWnd)
{
m_pOwner=pWnd;
}
int CSerialPort::GetPort(void)
{
return m_nPort;
}
BOOL CSerialPort::OpenPort(CWnd* pPortOwner,
UINT portnr,
UINT baud,
char parity,
UINT databits,
UINT stopbits,
UINT timeout,
DWORD dwCommEvents, UINT writebuffersize) // size to the writebuffer
{
if (m_hComm)
{
ClosePort();
Sleep(1000);
}
if (InitPort(pPortOwner, portnr, baud, parity, databits, stopbits, timeout, dwCommEvents, writebuffersize))
{
StartMonitoring();
return TRUE;
}
else return FALSE;
}
int CSerialPort::LanuchCommand(unsigned char* cmd, int len, unsigned char* pRecBuff, LCFLAG *pFlag)
{
int recvlen = 0;
if (m_hComm&&m_hComm != INVALID_HANDLE_VALUE)
{
EnterCriticalSection(&m_csIFSync);
BOOL bSucc = FALSE;
int retry = pFlag->retry;
do
{
EnterCriticalSection(&m_csCommunicationSync);
// m_pRecvBuff = pRecBuff;
m_RecvLen = 0;// &recvlen;
LeaveCriticalSection(&m_csCommunicationSync);
ResetEvent(m_hRecvEvent);
WriteBin2Port(cmd, len);
while (1)
{
if (retry) retry--;
if (WAIT_OBJECT_0 == WaitForSingleObject(m_hRecvEvent, pFlag->timeout))
{
EnterCriticalSection(&m_csCommunicationSync);
// 如果返回值长度等于设定的字节长度
if (m_RecvLen >= pFlag->len)
{
memcpy(pRecBuff, m_pRecvBuff, recvlen = m_RecvLen);
bSucc = TRUE;
}
LeaveCriticalSection(&m_csCommunicationSync);
ResetEvent(m_hRecvEvent);
if (bSucc)
{
retry = 0;
break;
}
}
else break;
}
} while (!bSucc && retry);
LeaveCriticalSection(&m_csIFSync);
}
return recvlen;
}
使用方法
使用InitPort初始化串口，返回值为BOOL类型，TRUE表示初始化正常，串口打开成功，否则失败。
CSerialEx* pEx = (CSerialEx*)pParam;
// 初始化串口
if (pEx->m_Port.InitPort(NULL, pEx->m_serial.cfg.port,
BAUDRATES[pEx->m_serial.cfg.baudrate],
PARITY[pEx->m_serial.cfg.parity],
DATABITS[pEx->m_serial.cfg.databits],
STOPBITS[pEx->m_serial.cfg.stopbits]
)
)
{
pEx->m_Port.StartMonitoring(); //开启串口接收线程
pEx->m_bConnect = TRUE;
while (1)
{
Sleep(50);
Poll(pEx);
}
}
使用LaunchCommand函数实现发送与接收，返回值为接收数据字节长度
BYTE buff[8]; // 发送指令数组
BYTE recvBuff[1024]; // 接收指令数组
LCFLAG flag; // 结构体
int recvlen; // 接收字节长度
WORD wCrc; // crc校验位
int i = 0;
buff[i++] = pDevEx->Dev.addr; // 从站地址
buff[i++] = 0x03;
buff[i++] = 0x00;
buff[i++] = 0x09;
buff[i++] = 0x00;
buff[i++] = 0x01;
wCrc = GetCrcCode((const char*)buff, i); // 获取CRC校验
buff[i++] = LOBYTE(wCrc); // CRC低字节
buff[i++] = HIBYTE(wCrc); // CRC高字节
memset(&flag, 0, sizeof(LCFLAG));
memset(recvBuff, 0, 1024);
flag.len = 0x07; // 设定接收字节长度
flag.timeout = pEx->m_serial.cfg.timeout; // 设定接收超时时间，单位ms
flag.retry = 0x03; // 设定重发次数
recvlen = pEx->m_Port.LanuchCommand(buff, sizeof(buff), recvBuff, &flag); // 发送数据，返回值为接收数据的字节长度
// recvlen如果等于设定的接收字节长度且返回值的第一个字节等于从站地址，就认为接收发送正确
if (recvlen == 0x07 && recvBuff[0] == pDevEx->Dev.addr)
{
// 填写接收数据解析代码
// recvBuff为接收数据数组
}
其中GetCrcCode()代码如下所示
WORD GetCrcCode(const char* ptr, int len)
{
WORD wCrc = WORD(0xFFFF);
for (int i = 0; i<len; i++)
{
WORD wd = WORD(BYTE(ptr[i]));
wCrc ^= wd; // 异或运算符
for (int j = 0; j<8; j++)
{
if (wCrc & 1)
{
wCrc >>= 1; // 右移一位
wCrc ^= 0xA001;
}
else{
wCrc >>= 1;
}
}
}
return wCrc;
}
结论
1）Modbus协议的在发送指令确定的前提下，接收数据的长度是可以确定的，等于0x05+读写寄存器个数*2，所以可以利用这一点来确定串口接收字节的长度，在SerialPort.cpp的LaunchCommand函数中可以看到if (m_RecvLen >= pFlag->len)这样一条判断语句。
2）LCFLAG结构体定义了发送和接收指令的一个附加属性结构体，其中type表示协议，len表示接收数据长度，buff[32]保留功能，timeout表示接收超时时间，retry表示重发次数。在发送指令之前，必须初始化该结构体，如果是Modbus协议，必须给结构体的len赋值，且该值必须等于接收数据的字节长度。
3）读者可以尝试自己改写LaunchCommand函数，实现诸如标准的SCPI协议或者各类自定义协议的串口编程，只要给LCFLAG的type指定一种协议，在LauncCommand函数中去根据type指定的协议添加适合的代码去完成数据的接收。
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