Serial Programming the Win32 api

I am having a lot of trouble opening up a serial communications port with win32 in VC++ 6.0.


This is the following code I have. It is in a very standard win32 application, one that just displays hello world (at this point, I am just trying to get the thing opened).
The following is under a WM_CREATE message. The handlePort and config are instantiated before the switch messsage in the WndProcedure as a HANDLE and DCB respectively.

Code:

---

handlePort = CreateFile("COM1", GENERIC_READ,0,NULL,OPEN_EXISTING,FILE_FLAG_OVERLAPPED,NULL);   
                if (handlePort = INVALID_HANDLE_VALUE){
                        if(GetLastError()==ERROR_FILE_NOT_FOUND){
                                MessageBox(hWnd,"MAy","May",MB_OK);
                        }else{
                        MessageBox(hWnd,"OKAY","OKAY",MB_OK);
                        }
                }
                GetCommState(handlePort,&config);
                config.BaudRate = 38400;
                config.Parity = NOPARITY;
                config.ByteSize = 8;
                config.StopBits = 1;
                SetCommState(handlePort, &config);

                // instance an object of COMMTIMEOUTS.
                COMMTIMEOUTS comTimeOut;                 
                // Specify time-out between charactor for receiving.
                comTimeOut.ReadIntervalTimeout = 3;
                // Specify value that is multiplied
                // by the requested number of bytes to be read.
                comTimeOut.ReadTotalTimeoutMultiplier = 3;
                // Specify value is added to the product of the
                // ReadTotalTimeoutMultiplier member
                comTimeOut.ReadTotalTimeoutConstant = 2;
                // Specify value that is multiplied
                // by the requested number of bytes to be sent.
                comTimeOut.WriteTotalTimeoutMultiplier = 3;
                // Specify value is added to the product of the
                // WriteTotalTimeoutMultiplier member
                comTimeOut.WriteTotalTimeoutConstant = 2;
                // set the time-out parameter into device control.
                SetCommTimeouts(handlePort,&comTimeOut);

---

Can anyone tell me what is wrong with my code?

So what's the problem you are having?

I wouldn't mess with the timeouts - since you're using overlapped I/O, you are already in control of any timeouts by virtue of waiting on read/write completion and "giving up" when you want.

gg

Code:

---


FILE* pWrite = NULL;
FILE* pRead = NULL;
 
pWrite = fopen("COM1:" , "w+b");
pRead = fopen("COM1:" , "r+b");
 
// use them as normal streams
 
fclose(pRead);
fclose(pWrite);

---

its just that simple.

What exactly is failing?

I see two things off the top of my head.....

Not setting the size of the DCB DCBlength prior to getting the port settings. Tells GetCommState which version of the structure you are using.

Setting the timeouts very low, they are in millisec, not seconds. I do not think yours will work.

You're also not setting the flow control.

gg

In case you're trying to write, you only open for reading.

gg