最近我在用电台对外发送数据以及接收数据的时候，遇到了一个很棘手的问题，最后用示波器才找到了解决问题的办法，在此特写此文章，以避免大家再出现这样的问题而没法解决了，如有不对，还请多多指教.。
其实用无线电台进行发送数据以及接收数据，只是对串口进行读写数据，但是有一点不同的是需要注意RTS(Request to send)，一般情况下我们在用电台发送数据的之前的时间把RTS置为Enable，但这个时间不能太长，然后发送完毕的时候再设Disable， 我在写程序的时候 ，就有一个这样的错误。
在没有发送完数据的时候，就把RTS设为 Disable，这样导致数据没有被完整的发送完毕，但RTS置的时间不能太长，不然表示常发数据，时间长了，会把电台烧坏的．写串口用的是大家都很熟悉的CSerialPort ，我在些基础改了一些东西。
下面的一开始的是发送一个字节的数据所需的时间(ms)， 首先是算出你发送一个字节的数据实际是多少个位，假设数据长度是8个位，一个起始位，一个终止位，如果有校验位的话，就是11位，算出每个字节所需的时间，这里这个RTS Enable 的时间应该稍比算出来的时间长一点，下面还有一些自己写的方法，以有用电台写数据的代码：
BOOL CSerialPort::InitPort(CWnd *pPortOwner，UINT portnr/* =-1 */，UINT baud/* =19200 */，char parity/* =’N’ */，UINT databits/* =8 */，UINT stopbits/* =1 */，DWORD dwCommEvents/* =EV_RXCHAR|EV_CTS */，UINT nBufferSize/* =512 */)
{
assert(portnr > 0 && portnr < 5);
assert(pPortOwner != NULL);
//Calculate the time that delay time.
int nTotalBits =0;
nTotalBits+=databits;
nTotalBits+=stopbits;
if (parity!=’N’)
nTotalBits+=1;
//Add a start bit.
nTotalBits+=1;
//Use millisecond unit.
nTotalBits*=1000;
nTotalBits+=baud;
m_uElapseTime = nTotalBits/baud;
// if the thread is alive: Kill
if (m_bThreadAlive)
{
do
{
SetEvent(m_hShutdownEvent);
} while (m_bThreadAlive);
TRACE("Thread endedn");
}
// 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_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_csCommunicationSyn);
// set buffersize for writing and save the owner
m_pOwner = pPortOwner;
if (m_szWriteBuffer != NULL)
delete [] m_szWriteBuffer;
m_szWriteBuffer = new BYTE[nBufferSize];
m_nPortNr = portnr;
m_nWriteBufferSize = nBufferSize;
m_dwCommEvents = dwCommEvents;
BOOL bResult = FALSE;
char *szPort = new char[50];
char *szBaud = new char[50];
// now it critical!
EnterCriticalSection(&m_csCommunicationSyn);
// 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=%d stop=%d"， baud， parity， databits， stopbits);
TRACE("%sn"，szBaud);
// 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 = 1000;
m_CommTimeouts.ReadTotalTimeoutMultiplier = 1000;
m_CommTimeouts.ReadTotalTimeoutConstant = 1000;
m_CommTimeouts.WriteTotalTimeoutMultiplier = 1000;
m_CommTimeouts.WriteTotalTimeoutConstant = 1000;
// 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!
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_csCommunicationSyn);
TRACE("Initialisation for communicationport %d completed.nUse Startmonitor to communicate.n"， portnr);
return TRUE;
}
void CSerialPort ::SetRTSEnable()
{
if (m_hComm == NULL) return;
GetCommState(m_hComm，&m_dcb);
if (m_dcb.fRtsControl ==RTS_CONTROL_ENABLE) return;
else
{
//Set the RTS enable.
m_dcb.fRtsControl =RTS_CONTROL_ENABLE;
SetCommState(m_hComm，&m_dcb);
}
}
void CSerialPort ::SetRTSDisable()
{
if (m_hComm == NULL) return;
GetCommState(m_hComm，&m_dcb);
if (m_dcb.fRtsControl ==RTS_CONTROL_DISABLE) return;
else
{
//Set the RTS enable.
m_dcb.fRtsControl =RTS_CONTROL_DISABLE;
SetCommState(m_hComm，&m_dcb);
}
}
//Get the RTS state .If I send data need a few time.
BOOL CSerialPort ::GetRTSState()
{
if (m_hComm == NULL) return FALSE;
DCB dcb;
GetCommState(m_hComm，&dcb);
if (dcb.fRtsControl == RTS_CONTROL_ENABLE)
return TRUE;
else if (dcb.fRtsControl == RTS_CONTROL_DISABLE)
return FALSE;
else return FALSE;
}
//Return the Elpase time that by the wireless.
UINT CSerialPort::GetSleepTime()
{
return m_uElapseTime;
}
//How to send data use wireless main station.
pFrame->m_pWireLessPort[j].SetRTSEnable();
Sleep(dwSleepTime);
pFrame->m_pWireLessPort[j].WriteToPort(pti->pData，pti->nDataLen);
//At 2005/1/20’s afternoon .When I send data by the wireless.
//At first ，I send data to the terminal ，the terminal receive
//data，but the terminal don’t back me any data.I don’t know how to
// deal with this problem.Finally ，the terminal designner Mr.Liu
//use the oscillograph ，then found Because the RTS enable time is too short.
//so that I don’t finish send data compeletly .So the the data that the terminal has
//received is not a integrated data.Although the terminal receive data
//but it is not a valid data .After I send data .then I need a few time to sleep.
//Get the baund of the COM.
DWORD dwSleepTime = pti->nDataLen*pFrame->m_pWireLessPort[j].GetSleepTime()+10;
Sleep(dwSleepTime);
pFrame->m_pWireLessPort[j].SetRTSDisable(); |
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