Why is my serial read application not responding? - c++

Question

I have written the following serial read function that is supposed to wait for the EV_RXCHAR event to be raised, after which it should read in a continuous loop
void CGCUGUIDlg::OnStartcom()
{
m_hComm = ::CreateFile(Com, //String that contains COM port name
GENERIC_READ|GENERIC_WRITE,
0,
0,
OPEN_EXISTING,
FILE_FLAG_OVERLAPPED,
0
);
fnCommState();
DCB dcb = {0};
dcb.DCBlength = sizeof(dcb);
Status = GetCommState(m_hComm, &dcb);
dcb.BaudRate = CBR_115200;
dcb.ByteSize = 8;
dcb.StopBits = ONESTOPBIT;
dcb.Parity = NOPARITY;
SetCommState(m_hComm, &dcb);
OVERLAPPED o;
BOOL fSuccess;
DWORD dwEvtMask;
DWORD NoBytesRead;
BYTE abBuffer[100];
fSuccess = SetCommMask(m_hComm,EV_RXCHAR);
if(!fSuccess)
{
MessageBox("SetCommMask failed with error %s",LPCTSTR(GetLastError()));
return;
}
o.hEvent = CreateFile(0,0,0,NULL,TRUE,FALSE,NULL);
o.Internal = 0;
o.InternalHigh = 0;
o.Offset = 0;
o.OffsetHigh = 0;
assert(o.hEvent);
for(;;)
{
if(WaitCommEvent(m_hComm,&dwEvtMask,&o)) //if 1
{
if(dwEvtMask & EV_RXCHAR) //if 2
{
do
{
ReadFile(m_hComm,&abBuffer,sizeof(abBuffer),&NoBytesRead,&o);
data.Append(LPCTSTR(abBuffer),NoBytesRead);
}//do
while(NoBytesRead>0);
if((data.GetAt(1)==10)&& data.GetLength() == 100) //if 3, EDIT 1
{
result = data;
this->SetDlgItemText(IDC_RXRAW,LPCTSTR(result));
this->UpdateDate(false); //EDIT 2
}//if 3
}//if 2
}//if 1
Sleep(40);
}//for
}
SOME DETAILS:
1 The application receives 100 bytes every 60 milliseconds, with no gap between bytes in those 100 bytes.
2 The header bytes are specified so I am doing a check for this and the message size.
3 Both data and result are CString variables.
4 Although I did not copy the code outright, I did base my code heavily on the monitoring code given here. This is why I am using an Overlapped method, even though I am only reading data.
The code compiles fine (big whoop, I know) but on running the application hangs when the function is called. I am using this emulator to send data.
Could someone point out the errors in my work?
UPDATE:
I tried to isolate the cause of my problem, so I tried to check if the EV_RXCHAR event was being called. I ran the following heavily shortened code:
for(;;)
{
if(WaitCommEvent(m_hComm,&dwEvtMask,0)) //if 1
{
if(dwEvtMask & EV_RXCHAR) //if 2
{
MessageBox("Data");
break;
}
break;
}
else
MessageBox("No Data");
break;
}//for
I am receiving the data, my code to handle the data is horrible. I am starting to work on this.
UPDATE 2: Still working on it, any input would be highly appreciated.