剛接觸串口編程，目的實作pc和arduino的通信，協議是自己制定的。pc端使用的VC++編程，網上下載的Serialport類，現在遇到了一個問題，一直沒解決。
問題是這樣的，點擊界面上的一些按鈕，pc給arduino（下位機，單片機而已）發送一幀資料，arduino端做出相應的處理并回傳應答幀，我用串口除錯助手觀察pc發的資料一直沒問題，單片機端應答的資料用串口除錯助手看也沒問題。但是用pc和arduino通信時會出現發送幾幀資料后出現pc接收的應答幀資料全部為0的情況，之后再次發送，m_hWriteEvent被設定為有信號，但是Event = WaitForMultipleObjects(3, port->m_hEventArray, FALSE, INFINITE)等到的始終是接收的事件，實在不知道是什么原因了。自己剛接觸很多東西也不懂，就是瞎弄的，懇請各位指點迷津。我先附上serialport.cpp代碼，如果需要再附其他代碼。感謝
剛接觸串口編程，目的實作pc和arduino的通信，協議是自己制定的。pc端使用的VC++編程，網上下載的Serialport類，現在遇到了一個問題，一直沒解決。
問題是這樣的，點擊界面上的一些按鈕，pc給arduino（下位機，單片機而已）發送一幀資料，arduino端做出相應的處理并回傳應答幀，我用串口除錯助手觀察pc發的資料一直沒問題，單片機端應答的資料用串口除錯助手看也沒問題。但是用pc和arduino通信時會出現發送幾幀資料后出現pc接收的應答幀資料全部為0的情況，之后再次發送，m_hWriteEvent被設定為有信號，但是Event = WaitForMultipleObjects(3, port->m_hEventArray, FALSE, INFINITE)等到的始終是接收的事件，實在不知道是什么原因了。自己剛接觸很多東西也不懂，就是瞎弄的，懇請各位指點迷津。我先附上serialport.cpp代碼，如果需要再附其他代碼。感謝
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#include "stdafx.h"
#include "SerialPort.h"
#include <assert.h>
#define COM_BUFFER_SIZE 256
CSerialPort::CSerialPort()
{
m_hComm = NULL; //埠號
// 初始化 OVERLAPPED結構體（異步I/O模型）
m_ov.Offset = 0;
m_ov.OffsetHigh = 0;
// 初始化事件
m_ov.hEvent = NULL; //標識事件,資料傳送完成時把它設為信號狀態
m_hWriteEvent = NULL; //寫入串口事件
m_hShutdownEvent = NULL; //關閉執行緒事件
m_WriteBuffer = NULL;
m_nWriteSize=1;
m_bThreadAlive = FALSE; //執行緒是否正在運行。初始化為FALSE
}
CSerialPort::~CSerialPort()
{
//如果執行緒還在運行，把m_hShutdownEvent設定為有信號，關閉執行緒
do
{
SetEvent(m_hShutdownEvent);
} while (m_bThreadAlive);
//判斷埠是否還開著，如果開著就關閉它。
if (m_hComm != NULL)
{
CloseHandle(m_hComm);
m_hComm = NULL;
}
// Close Handles
if(m_hShutdownEvent!=NULL)
CloseHandle( m_hShutdownEvent);
if(m_ov.hEvent!=NULL)
CloseHandle( m_ov.hEvent );
if(m_hWriteEvent!=NULL)
CloseHandle( m_hWriteEvent );
TRACE("Thread ended\n"); //除錯宏
delete [] m_WriteBuffer;
}
//
// Initialize the port. This can be port 1 to 4.
//
BOOL CSerialPort::InitPort(CWnd* pPortOwner, // the owner (CWnd) of the port (receives message)
UINT portnr, // portnumber (1..4)
UINT baud, // baudrate
char parity, // parity
UINT databits, // databits
UINT stopbits, // stopbits
DWORD dwCommEvents, // EV_RXCHAR, EV_CTS etc
UINT writebuffersize) // size to the writebuffer
{
assert(portnr > 0 && portnr < 5); //斷言，埠號必須是1-4；
assert(pPortOwner != NULL); //埠不能為空
// if the thread is alive: Kill
if (m_bThreadAlive)
{
do
{
SetEvent(m_hShutdownEvent);
} while (m_bThreadAlive);
TRACE("Thread ended\n");
}
// 創建事件
if (m_ov.hEvent != NULL)
ResetEvent(m_ov.hEvent); //設定為無信號狀態
else
m_ov.hEvent = CreateEvent(NULL, TRUE, FALSE, NULL);//創建事件，設定為有信號狀態
if (m_hWriteEvent != NULL)
ResetEvent(m_hWriteEvent);
else
m_hWriteEvent = CreateEvent(NULL, TRUE, FALSE, NULL);
if (m_hShutdownEvent != NULL)
ResetEvent(m_hShutdownEvent);
else
m_hShutdownEvent = CreateEvent(NULL, TRUE, FALSE, NULL);
// initialize the event objects
//用于主執行緒判斷I/O事件（關閉串口，接收訊息，寫入訊息）
//m_hEventArray[0] = m_hShutdownEvent; // highest priority
//m_hEventArray[1] = m_ov.hEvent;
//m_hEventArray[2] = m_hWriteEvent;
m_hEventArray[0] = m_hShutdownEvent; // highest priority
m_hEventArray[1] = m_hWriteEvent;
m_hEventArray[2] = m_ov.hEvent;
// 初始化臨界區
InitializeCriticalSection(&m_csCommunicationSync);
// set buffersize for writing and save the owner
m_pOwner = pPortOwner;
if (m_WriteBuffer != NULL)
delete [] m_WriteBuffer;
m_WriteBuffer = new BYTE[writebuffersize];
m_nPortNr = portnr;
m_nWriteBufferSize = writebuffersize;
m_dwCommEvents = dwCommEvents;
BOOL bResult = FALSE;
char *szPort = new char[50]; //埠號
char *szBaud = new char[50]; //波特率
// 進入臨界區
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(szPort, "COM%d", portnr);
sprintf(szBaud, "baud=%d parity=%c data=https://bbs.csdn.net/topics/%d stop=%d", baud, parity, databits, stopbits);
// get a handle to the port
m_hComm = CreateFile(szPort, // communication port string (COMX) 指向檔案名的指標
GENERIC_READ | GENERIC_WRITE, // read/write types 訪問模式（寫 / 讀）
0, // comm devices must be opened with exclusive access 共享模式
NULL, // no security attributes 指向安全屬性的指標
OPEN_EXISTING, // comm devices must use OPEN_EXISTING 如何創建
FILE_ATTRIBUTE_NORMAL | FILE_FLAG_OVERLAPPED, // Async I/O 檔案屬性
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 = 0x100;
m_CommTimeouts.ReadTotalTimeoutMultiplier = 2;
m_CommTimeouts.ReadTotalTimeoutConstant = 5000;
m_CommTimeouts.WriteTotalTimeoutMultiplier = 10;
m_CommTimeouts.WriteTotalTimeoutConstant =3000;
// 設定超時引數，設定事件，配置DCD
if (SetCommTimeouts(m_hComm, &m_CommTimeouts)) //設定通訊設備讀寫時的超時引數
{
if (SetCommMask(m_hComm, dwCommEvents)) //設定事件，在讀寫串口之前，需要用SetCommMask ()函式設定事件掩模來監視指定通信埠上的事件
{
if (GetCommState(m_hComm, &m_dcb)) //用當前控制的一個指定通訊設備來填充一個設備控制塊
{
m_dcb.EvtChar = 'q';
m_dcb.fRtsControl = RTS_CONTROL_ENABLE; // set RTS bit high! RTS-Request To Send
if (BuildCommDCB(szBaud, &m_dcb)) // 填充指定的DCD
{
if (SetCommState(m_hComm, &m_dcb)) //根據一個設備控制塊（一個DCB結構體）中的規范說明來配置一個通訊設備
; // normal operation... continue
else
ProcessErrorMessage("SetCommState()");
}
else
ProcessErrorMessage("BuildCommDCB()");
}
else
ProcessErrorMessage("GetCommState()");
}
else
ProcessErrorMessage("SetCommMask()");
}
else
ProcessErrorMessage("SetCommTimeouts()");
delete [] szPort;
delete [] szBaud;
// 清慷訓沖區
PurgeComm(m_hComm, PURGE_RXCLEAR | PURGE_TXCLEAR | PURGE_RXABORT | PURGE_TXABORT);
// 離開臨界區
LeaveCriticalSection(&m_csCommunicationSync);
//程式除錯宏TRACE
TRACE("Initialisation for communicationport %d completed.\nUse Startmonitor to communicate.\n", portnr);
return TRUE;
}
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//串口執行緒函式
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;
static COMSTAT comstat; //通信設備資訊
BOOL bResult = TRUE;
// Clear comm buffers at startup
if (port->m_hComm) // check if the port is opened
//清空指定資源的輸入輸出快取
PurgeComm(port->m_hComm, PURGE_RXCLEAR | PURGE_TXCLEAR | PURGE_RXABORT | PURGE_TXABORT);
// 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!
//為一個特指的通信設備等待一個事件發生，該函式所監控的事件是與該設備句柄相關聯的一系列事件
//WaitCommEvent()函式來等待串口上我們利用SetCommMask ()函式設定的事件
bResult = WaitCommEvent(port->m_hComm, &Event, &port->m_ov);
if (!bResult)
{
// If WaitCommEvent() returns FALSE, process the last error to determin
// the reason..
//檢索呼叫執行緒的最后錯誤代碼值
switch (dwError = GetLastError())
{
case ERROR_IO_PENDING: //重疊I/O正在進行中
{
// 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.
//在使用ReadFile 函式進行讀操作前，應先使用ClearCommError函式清除錯誤
bResult = ClearCommError(port->m_hComm, &dwError, &comstat);
if (comstat.cbInQue == 0) //判斷接收的字符數是否為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); //等待事件
switch (Event)
{
case 0:
{
// Shutdown event. This is event zero so it will be
// the higest priority and be serviced first.
CloseHandle(port->m_hComm);
port->m_hComm=NULL;
port->m_bThreadAlive = FALSE;
// Kill this thread. break is not needed, but makes me feel better.
AfxEndThread(100);
break;
}
case 1: // write event
{
// Write character event from port
Write(port);
break;
}
case 2: // read event
{
GetCommMask(port->m_hComm, &CommEvent); //獲取串口當前的設定的通訊事件
if (CommEvent & EV_RXCHAR)
// Receive character event from port.
{
Receive(port, comstat);
}
if (CommEvent & EV_CTS)
::SendMessage(port->m_pOwner->m_hWnd, WM_COMM_CTS_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_RXFLAG)
::SendMessage(port->m_pOwner->m_hWnd, WM_COMM_RXFLAG_DETECTED, (WPARAM) 0, (LPARAM) port->m_nPortNr);
break;
}
//case 2: // write event
// {
// // Write character event from port
// Write(port);
// break;
// }
} // end switch
} // close forever loop
return 0;
}
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//啟動執行緒
BOOL CSerialPort::StartMonitoring()
{
if (!(m_Thread = AfxBeginThread(CommThread, this)))
return FALSE;
TRACE("Thread started\n");
return TRUE;
}
//開始執行緒
BOOL CSerialPort::RestartMonitoring()
{
TRACE("Thread resumed\n");
m_Thread->ResumeThread();
return TRUE;
}
//暫停執行緒
BOOL CSerialPort::PauseMonitoring()
{
TRACE("Thread suspended\n");
m_Thread->SuspendThread();
return TRUE;
}
//停止執行緒
BOOL CSerialPort::StopMonitoring()
{
// 強制性關閉執行緒
::TerminateThread (m_Thread, 0);
// 獲取退出代碼
DWORD dwExitCode;
::GetExitCodeThread (m_Thread, &dwExitCode);
//如果執行緒還在運行，再嘗試關閉一次
if ( STILL_ACTIVE == dwExitCode )
{
Sleep(1000);
::TerminateThread (m_Thread, 0);
}
m_Thread = NULL;
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(Temp, "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::Write(CSerialPort* port)
{
BOOL bWrite = TRUE;
BOOL bResult = TRUE;
DWORD BytesSent = 0;
ResetEvent(port->m_hWriteEvent); //設定為無信號
// 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);
//從檔案指標指向的位置開始將資料寫入到一個檔案中, 且支持同步和異步操作,
bResult = WriteFile(port->m_hComm, // Handle to COMM Port
port->m_WriteBuffer, // Pointer to message buffer in calling finction
// strlen((char*)port->m_szWriteBuffer), // Length of message to send
port->m_nWriteSize, // 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: //重疊I/O正在進行
{
// 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;
//回傳重疊操作的結果，用來判斷異步操作是否完成，它是通過判斷OVERLAPPED結構中的hEvent是否被置位來實作的
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_nWriteSize) // Length of message to send)
{
TRACE("WARNING: WriteFile() error.. Bytes Sent: %d; Message Length: %d\n", BytesSent, strlen((char*)port->m_WriteBuffer));
}
// ::SendMessage((port->m_pOwner)->m_hWnd, WM_COMM_TXEMPTY_DETECTED, (WPARAM) RXBuff, (LPARAM) port->m_nPortNr);
// ::SendMessage((port->m_pOwner)->m_hWnd, WM_COMM_TXEMPTY_DETECTED,0,(LPARAM) port->m_nPortNr);
}
//重疊I/O非常靈活，它也可以實作阻塞（例如我們可以設定一定要讀取到一個資料才能進行到下一步操作）
void CSerialPort::Receive(CSerialPort* port, COMSTAT comstat)
{
BOOL bRead = TRUE;
BOOL bResult = TRUE;
DWORD dwError = 0;
DWORD BytesRead = 0;
for (;;)
{
unsigned char RXBuff[COM_BUFFER_SIZE];
// Gain ownership of the comm port critical section.
// This process guarantees no other part of this program
// is using the port object.
//進入臨界區
EnterCriticalSection(&port->m_csCommunicationSync);
// ClearCommError() will update the COMSTAT structure and
// clear any other errors.
//在使用ReadFile 函式進行讀操作前，應先使用ClearCommError函式清除錯誤
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)
{
memset (RXBuff, 0, COM_BUFFER_SIZE);
//memset (&port->m_ov, 0, sizeof (port->m_ov));
//ReadFile函式從檔案指標指定的位置讀取資料
bResult = ReadFile(port->m_hComm, // Handle to COMM port
RXBuff, // RX Buffer Pointer
COM_BUFFER_SIZE, // Read byte Size
&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: //重疊I/O正在進行
{
// asynchronous i/o is still in progress
// Proceed on to GetOverlappedResults();
//回傳重疊操作的結果，用來判斷異步操作是否完成，它是通過判斷OVERLAPPED結構中的hEvent是否被置位來實作的
while (!GetOverlappedResult(port->m_hComm, // Handle to COMM port
&port->m_ov, // Overlapped structure
&BytesRead, // Stores number of bytes read
TRUE))
{
dwError = GetLastError();
if(dwError == ERROR_IO_INCOMPLETE) //重疊 I/O 事件不在信號狀態中
{
continue;
}
else
{
bRead = FALSE;
ClearCommError(port->m_hComm, &dwError, &comstat);
break;
}
}
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;
//回傳重疊操作的結果，用來判斷異步操作是否完成，它是通過判斷OVERLAPPED結構中的hEvent是否被置位來實作的
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)
LeaveCriticalSection(&port->m_csCommunicationSync);
// notify parent that a byte was received
::SendMessage((port->m_pOwner)->m_hWnd, WM_COMM_RXCHAR, (WPARAM) RXBuff, (LPARAM) port->m_nPortNr);
} // end forever loop
}
uj5u.com熱心網友回復：
這種東西網上一大堆源代碼。單步除錯看看哪里出問題了。uj5u.com熱心網友回復：
單步除錯沒問題啊 例外時顯示資料收到的全部為0 但問題是下位機發送的資料不是0啊
uj5u.com熱心網友回復：
你用串口除錯助手打開有沒有問題？這是別人寫的代碼http://download.csdn.net/detail/ilikehigame/5895559uj5u.com熱心網友回復：
以前碰到過兩邊波特率不匹配的問題。uj5u.com熱心網友回復：
建議使用OpenDev框架中的libComm通信庫http://www.cnblogs.com/EdmundDwyane/p/5503578.html
uj5u.com熱心網友回復：
試試拉長與下位機的通信間隔時間試試看， 是否存在 幀快取溢位、幀覆寫等 幀粘連等問題？推薦BusHound 之類的輔助工具先監控下通信的資料 可幫助分析
uj5u.com熱心網友回復：
使用portmon軟體輔助除錯串口通訊程式。轉載請註明出處，本文鏈接：https://www.uj5u.com/gongcheng/145278.html
標籤：硬件/系統