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Neil P. · Guest

I am not sure if this is the right newsgroup, but I don't know where to post
this one?

I have an application where I write to the comm port and read from it. I am
currently experiencing a problem, where I send a byte then wait for the unit
to respond with a byte, but it gets there about 10 secs later.

I am looking at the que, to signal if there is something to read, but
nothing gets qued? I know that the other system is sending it immediately
(less than 1 sec) after it recieves my byte.

What could be happening? Is there a priority setting I am suppose to set to
make my communication priority over a mouse movement or any other system
process?

Thank you,
Neil P.

Bob Gonder · Guest

Neil P. wrote:

Neil P. · Guest

I use ClearCommError(hComm, &dwErrorMask, & Comstat)

to view what is coming in the cbInQue,

Once, I detect there is something in the que, I
use ReadFile(hComm, inbuff, nBytes, &nBytesRead, &overlapped), I am in this
routine upto 2 times the amount of bytes coming in, using my baudrate 9600.
So I beleive there is plenty of time so that byte can be placed in the que
buffer.

If the unit sending the byte responds ( in a millisecond), then how long is
it before Windows reports to the ClearCommError or to the struct_COMSTAT
that there is a byte waiting? Does Windows take more than a second to place
it on the que?

By the way the unit is always responding with one byte, because is the
response of what I am sending it.

Thank you,
Neil P.

Remy Lebeau (TeamB) · Guest

"Neil P." <nporve01 (AT) hotmail (DOT) com> wrote

Neil P. · Guest

Well, I am using overlapped I/O. The problem is that I don't want my code
to lock up.
If the other unit does not respond, I want the read function to quit, but
what is a good time to quit?
How about if I dishout an application that works well with this unit, under
the environment I am in, but
when the user gets it, the unit or my application seems that it is lockout
(because he/she has a pentium 100, operating on Win95)? <---- Just an
example.

I was using the WaitForSingleObject(), but it did not make a difference,
where I enabled it or not?

Anyways, lets see if I can display a snippet from my code.

Thank you,
Neil P.

"Remy Lebeau (TeamB)"

Bob Gonder · Guest

Neil P. wrote:

Neil P. · Guest

Here is a snippet of my code and exactly what I am doing:

1. Is where I am writing and reading.
2. Is my actual read.

// Set the unit on programming mode
clComm.Write("C",1);

do
{
clComm.Read(1);
cResponse = NULL;
cResponse = clComm.cTransBuff;
if (iRead_Tries >= 3)
goto No_Response;
iRead_Tries++;
}
// Wait for 0x0D
while (cResponse[0] != 0x0D);

//--------------------------------------------------------------------------
----
// Read from COM port
//--------------------------------------------------------------------------
----
void __fastcall Comm::Read(unsigned int iExpected)
{
// Initialize
iCollectBytes = 0;
dwActualBytesRead = 0;
bStop_Read = false;
COMSTAT comstat; // Structure of the communication device

// Do we have the handle ?
if (hComm)
{ // Begin if statement (Handle)

// Clear the buffers
for (int i = 0; i <= (BUFSIZE - 1); i++)
bCommData[i] = NULL;
for (int i = 0; i <= (BUFSIZE - 1); i++)
cTransBuff[i] = NULL;

// Set a safety timeout
dwRead_Time_Out = GetTickCount() + (iExpected*2);

// Stop read flag
while (bStop_Read == false)
{ // Begin while statement (Stop Read Flag)

// Do we have the handle ?
//if (hComm)
// Clear any communication error & return # of bytes in the input
buffer
ClearCommError(hComm, // handle to communications device
&dwError, // pointer to variable to receive error
codes
&comstat); // pointer to buffer for communications
status

// Is there anything waiting to be read (BUFSIZE bytes match
cCommData
//capability)
if ((comstat.cbInQue >= iExpected) && (comstat.cbInQue <= BUFSIZE))
{ // Begin if statement (InQue)

// Do we have the handle ?
//if (hComm)
// Read the data from the serial port
if (!ReadFile (hComm,
bCommData,
comstat.cbInQue,
&dwBytesTransferred,
&o))

{ // Begin if statement (read error)

// Check if error is Overlapped I/O pending
if (!(GetLastError() == ERROR_IO_PENDING))

// Report the error
ReportError();

} // End if statement (read error)

else
{ // Begin else statement (Bytes are waiting)

// Return the number of bytes that were read
GetOverlappedResult(hComm,
&o,
&dwActualBytesRead,
FALSE);

// Are there bytes waiting and check if buffer is not overrun
if ((dwActualBytesRead != 0) && (dwActualBytesRead <= BUFSIZE))
{ // Begin if statement (actual bytes read)

// Start the collection of bytes
for (unsigned int i = 0; i <= (dwActualBytesRead - 1); i++)
{ // Begin for statement (byte collect)

// Copy the data to the return variable
cTransBuff[iCollectBytes++] = bCommData[i];

} // End for statement (byte collect)

} // End if statement (actual bytes read)

} // End else statement (Byte are waiting)
} // End if statement (InQue)

// Safety timeout check
if (dwRead_Time_Out <= GetTickCount())
// End the read while loop
bStop_Read = true;

} // End while statement (Stop Read Flag)
} // End if statement (Handle)
}

It probably looks pretty weird, but I am not an expert. It works if
iRead_Tries is a number like 10, but that means according to my code that if
I am running my communication at 9600 baud, and I am expecting 1 byte and I
am multiplying by two, enough so that it will read it the first time and not
even have to get to three.
So I believe, that Windows does not report right away to the struct
__COMSTA, there is actually a delay of some sort? I can't put my finger on
it, but maybe you guys can see something I am doing wrong with this snippet
of code.

By the way, I am not always expecting one byte coming back, that is why, my
readfile has comstat.cbInQue, as the number of bytes to read.

Thank you,
Neil P.

Bob Gonder · Guest

Neil P. wrote:

Bob Gonder · Guest

Neil P. wrote:

Remy Lebeau (TeamB) · Guest

"Neil P." <nporve01 (AT) hotmail (DOT) com> wrote

Remy Lebeau (TeamB) · Guest

"Bob Gonder" <notbg (AT) notmindspring (DOT) invalid> wrote

Bob Gonder · Guest

Remy Lebeau (TeamB) wrote:

Neil P. · Guest

I like to thank everyone for helping me.

I hope the code snippet did not confuse anyone, and I know I might not be
doing things right, but I am trying to correct my mistakes.

I don't use CheckCommStatus() anywhere in my snippet?

Jonathan Benedicto · Guest

"Neil P." <nporve01 (AT) hotmail (DOT) com> wrote

Remy Lebeau (TeamB) · Guest

"Neil P." <nporve01 (AT) hotmail (DOT) com> wrote