Re: Multi Threading Issue

From:

"Alexander Grigoriev" <alegr@earthlink.net>

Newsgroups:

microsoft.public.vc.language

Date:

Fri, 1 Dec 2006 19:32:08 -0800

Message-ID:

<esdRuIcFHHA.3872@TK2MSFTNGP06.phx.gbl>

If you're using serial port, make sure you open the handle with
FILE_FLAG_OVERLAPPED, and use proper OVERLAPPED argument for read and write
operations. Otherwise all operations are serialized and you won't be able to
write data while a read operation is in progress.

"Nathan Smith" <NathanSmith@discussions.microsoft.com> wrote in message
news:FAEBAE47-C2CF-4E5C-A246-FB068F34887D@microsoft.com...

I put an o-scope on the transmit lines from the device and I see that the
device is sending the data 1-2ms after the data is received from the app,
so
I know the device is sending the data.

I can also verify the data is there by increasing the ping rate to
something
like every 20ms and the data is read in right after the ping is sent. So
there's some sort of interaction between the threads that I can't figure
out.

"Eric Hill" wrote:

There are 2 threads that handle transfer of data. One handles transfer
of
data to the printer and the other handles pinging the device. The ping
thread is held off using Sleep while the app is sending data to the
device.
So the threads are not writing to the same port simultaneously.

You should the handle to the serial port with a critical section to
ensure
that two threads don't write to the port at the same time. But even so,
that doesn't explain the delay in receiving the other request until a
ping
happens.

Can you sniff the serial data and see what is actually going on? It may
be that the data isn't getting into the serial buffer, or maybe isn't
even
being sent for some reason. Try to narrow the problem down a bit more,
because from what you've said, it should be working... :)

Eric