hang up in WriteFile() if WaitCommEvent() is active in receive thread

[Elmar Jacobs]

hi folk,

if I define a SetCommMask for the receive event and the thread is waiting
for an Rx Event the writeFile function will hang up if I try to send byte.
I use the standard settings for the port. Can anybody tell me why the
WriteFile function hang up?


thanks a lot,
elmar

GetCommTimeouts(m_hComPort, &cto);

// Change the COMMTIMEOUTS structure settings.
cto.ReadIntervalTimeout = MAXDWORD;
cto.ReadTotalTimeoutMultiplier = 0;
cto.ReadTotalTimeoutConstant = 0;
cto.WriteTotalTimeoutMultiplier = 0;//10;
cto.WriteTotalTimeoutConstant = 0;//1000;

// Set the time-out parameters for all read and write operations
// on the port.
SetCommTimeouts(m_hComPort, &cto);



DWORD WINAPI ReadThread(PVOID pArg)
{
HANDLE hSerPort = (HANDLE) pArg;
BOOL retVal;
//DWORD dwMask;

if (hSerPort != NULL){
rCntInBuffer = rCntOutBuffer = cntOfNotFetchedBytes = 0;

// Specify a set of events to be monitored for the port.
SetCommMask (hSerPort, EV_RXCHAR | EV_ERR);

do{
WaitCommEvent(hSerPort, &dwMask, 0);
switch (dwMask){
case EV_RXCHAR:
{
if (cntOfNotFetchedBytes < d_receiveBufferSize){ // if
receivedBuffer not full insert byte
do{
retVal = ReadFile(hSerPort, &receiveBuffer[rCntInBuffer], 1,
&numberOfReceiving, 0);
if (numberOfReceiving == 1){
rCntInBuffer++;
cntOfNotFetchedBytes++;

if (rCntInBuffer > d_receiveBufferSize){
rCntInBuffer = 0;
}
}
}while(retVal != NULL); // readFile untile fifo is empty
}
}
break;
case EV_ERR:
break;
}
}while(1);
}
return 0;
}

 

[Chris Tacke, eMVP]

Sounds like the driver doesn't support full duplex. Have you tried with any
of the well-tested serial libraries already out there (like the one from
OpenNETCF.org or Dick Grier)?

 

[Elmar Jacobs]

No I am not using one of this libraries.

How can I handle the 2 events EV_RXCHAR and a selfmade event EV_TXCHAR in
one thread, like :

{
.....
if ((WaitComEvent(hSerPort, &dwMask, o) || WaitForSingleEvent(EV_TXCHAR,
INFINITE)){
if (EV_TXCHAR){
...handel transmit event....
}else{
....handle receive event..
}

}
so that I can make an bye pass about the full dublex problem?
Do you mean it works?

elmar

 

[Chris Tacke, eMVP]

You really can't do send and receive on the same thread. If the driver
truly doesn't support full duplex, you'll have to change your waits from
INFINITE to a finite period then swap from send to receive mode and back
again (or define a communication protocol that prevents the possibility of
needing full duplex).

-Chris

 

[Elmar Jacobs]

thanks a lot Chris

- el

You really can't do send and receive on the same thread. If the driver
truly doesn't support full duplex, you'll have to change your waits from
INFINITE to a finite period then swap from send to receive mode and back
again (or define a communication protocol that prevents the possibility of
needing full duplex).

-Chris