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George · Guest

I'm am trying to do Overlapped I/O to the Serial Port. I set the Event
Mask to respond to a charater (EV_RXCHAR) moved to the input buffer. I've
tried implemting using the mutilple examples provided by Borland and
Microsoft. When there is no receive character , all objects on the form
seem just fines. Once a character is sent, the form seems to freeze, and
can only terminate the app through the debug reset.
Is there something obvious that I am not doing setting up or handling the
event, or direct me to more information.

Thanks

Remy Lebeau (TeamB) · Guest

"George" <George (AT) kallin (DOT) com> wrote

George · Guest

Thanks, more info the better.
I've attached the code...very simple.

void __fastcall TForm1::FormCreate(TObject *Sender)
{
HANDLE hCom;
OVERLAPPED o;
BOOL fSuccess;
DWORD dwEvtMask;
DCB dcb;

hCom = CreateFile("COM1",
GENERIC_READ | GENERIC_WRITE,
0, // Exclusive access
0, //default secuity attributes
OPEN_EXISTING,
FILE_FLAG_OVERLAPPED,
0
);

if (hCom == INVALID_HANDLE_VALUE)
{
//Handle the error
}

// Fill in the DCB: baud=9600, 8 data bits, no parity, 1 stop bit.

dcb.BaudRate = 9600;
dcb.ByteSize = 8;
dcb.Parity = NOPARITY;
dcb.StopBits = ONESTOPBIT;

fSuccess = SetCommState(hCom, &dcb);

if (!fSuccess)
{
// Handle the error.
}

// Set the evnt mask

fSuccess = SetCommMask(hCom, EV_RXCHAR);
if (!fSuccess)
{
// Handle the error
}

// Create an event object for use by WaitCommEvent.

o.hEvent = CreateEvent(
NULL, //default secutiry attribute
FALSE, // auto reset event
FALSE, // not signaled
NULL // no name
);

// Initialize the rest of the OVERLAPEPED truture to zero
o.Internal = 0;
o.InternalHigh = 0;
o.Offset = 0;
o.OffsetHigh = 0;
// o.hEvent = 0;

assert(o.hEvent);

char inBuffer[8] = "AB";
DWORD nBytesRead;
DWORD nBytesToRead = 0;

if (WaitCommEvent(hCom, &dwEvtMask, &o))
{
if (dwEvtMask & EV_RXCHAR)
{
nBytesToRead = 1;
fSuccess = ReadFile(hCom, &inBuffer, nBytesToRead,
&nBytesRead,&o) ;
Button1->Caption = "CHAR";
}
}
}

George

"Remy Lebeau (TeamB)" <no.spam (AT) no (DOT) spam.com> wrote

Remy Lebeau (TeamB) · Guest

"George" <George (AT) kallin (DOT) com> wrote

George · Guest

Remmy,

Using 'never' once is sufficient, thank you. I probably am in over my
head, but the attractiveness of Builder is that it so easy to use and see
immediate results. I've designed my micro to communicate over the Comm
port and understand the old ways (assembly) do not appy in the new Windows
enviornment.
I am controlling the receive characters, so I am not concerned with
reading multiple. When I can capture the event, then I can build the read
to handle any unsolicited characters. Now if you want to help, I would
appreciate your effort.
Yes, I am reading the article, and I have yet to see the errors of my
way.

Thank you,

George

"Remy Lebeau (TeamB)" <no.spam (AT) no (DOT) spam.com> wrote

Remy Lebeau (TeamB) · Guest

"George" <George (AT) kallin (DOT) com> wrote