Re: Reading Serial Port

From:

clinisbut <clinisbut@gmail.com>

Newsgroups:

microsoft.public.vc.mfc

Date:

Tue, 5 Feb 2008 06:19:58 -0800 (PST)

Message-ID:

<2658f726-3a6b-46ff-9c5d-136d4370cf65@k2g2000hse.googlegroups.com>

On Feb 5, 1:18 pm, "Scott McPhillips [MVP]" <org-dot-mvps-at-scottmcp>
wrote:

"clinisbut" <clinis...@gmail.com> wrote in message

news:e3bd3c90-b885-4c06-b526-65070a47e425@s12g2000prg.googlegroups.com...

Ok, I tried this:
I created two new events: ReaderStoped and WriterStoped.
In my reader-worker-thread:
Once the shutdown event is signaled, the loop breaks and reaches
this line:
SetEvent( ReaderStoped );

Same with Writer method.

Then, in my stop() method:
  SetEvent(ShutdownEvent);
  WaitForSingleObject( ReaderStoped, INFINITE ); //Just for
testing, I know I should call WaitForMultipleObjects with the events
ReaderStoped and WriterStoped.

  CloseHandle( ShutdownEvent );
  CloseHandle( hComm );
  CloseHandle( ReadEvent );
  CloseHandle( WriteEvent );
  CloseHandle( ReaderStoped );
  CloseHandle( WriterStoped );

  PostQuitMessage( 0 );

Why did you introduce the new 'Stoped' events? You had it right in the
previous message: WaitForSingleObject should wait on the thread handle.
These new events just add complexity and needlessly duplicate built-in
functionality.

And, as explained in my previous reply, you are not calling PostQuitMessage
from the thread that is quitting.

Here is a recipe, assuming that the CWinThread m_bAutoDelete is set to FALSE
at startup.

How to shut down a worker thread:
main thread does SetEvent(ShutdownEvent)
main thread does WFSO(pthread->m_hThread)
    worker thread senses ShutdownEvent with WFSO.
    worker thread returns from thread function.
main thread WFSO returns
main thread closes handles
main thread delete pthread

How to shut down a message-driven thread:
main thread PostThreadMessage with shut down message
main thread does WFSO(pthread->m_hThread)
    thread sees message, calls PostQuitMessage
main thread WFSO returns
main thread closes handles
main thread delete pthread

--
Scott McPhillips [VC++ MVP]

Buff... I'm very lost, I think I'm using this class in a wrong way,
let me show you my class (resumed and some parts regarding to serial
proceses ommited ) and exactly how I'm using it:

MySerial::MySerial
{ //nothing here
}
~MySerial::MySerial
{ //nothing here
}
BOOL MySerial::InitInstance()
{
        m_bAutoDelete = FALSE;
}
int MySerial::ExitInstance()
{
    return CWinThread::ExitInstance();
}

//Next are my two only messages I send from GUI thread
BEGIN_MESSAGE_MAP(MySerial, CWinThread)
    //{{AFX_MSG_MAP(MySerial)
        ON_THREAD_MESSAGE( WM_MYSERIAL_WRITE, OnWriteData )
    ON_THREAD_MESSAGE( WM_MYSERIAL_CLOSE, closePort )
END_MESSAGE_MAP()

int MySerial::Run()
{
    TRACE("Running.");
    return CWinThread::Run();
}

//Called when GUI sends WM_MYSERIAL_WRITE
void MySerial::OnWriteData( WPARAM wParam, LPARAM lParam )
{
   //A group of instructions, no loop.
   //Only called when, from my GUI I send
PostThreadMessage( WM_MY_SERIAL_WRITE )
}

UINT ReaderThread( LPVOID cT )
{
    //A group of instructions, inside a loop.
    //The loop exists when there is an error or ShutdownEvent is
signaled
    while( reading )
     {
        //Blablablablabla
     }
}

BOOL MySerial::openPort( int port )
{
        WriteEvent = CreateEvent( NULL, TRUE, FALSE, NULL );
    ReadEvent = CreateEvent( NULL, TRUE, FALSE, NULL );
        ShutdownEvent = CreateEvent( NULL, TRUE, FALSE, NULL );

        //Here I open my port and...
       //Start ReaderThread to continuosly read Serial Port
    AfxBeginThread( ReaderThread, this, THREAD_PRIORITY_NORMAL );
}

//This is my old Stop() method
void MySerial::closePort( WPARAM wparam, LPARAM lparam)
{
    if( opened) //A flag set to true when I open the port
    {
    SetEvent( ShutdownEvent );
    //WaitForSingleObject( ReaderStoped, INFINITE ); //No
ReaderStoped Event, no WFSO

        ::CloseHandle( WriteEvent );
    ::CloseHandle( ShutdownEvent );
    ::CloseHandle( ReadEvent );
    ::CloseHandle( hComm );

    PostQuitMessage(0);
    WaitForSingleObject( this->m_hThread, INFINITE );
    }
}

This is basically my class MySerial.

Then here it is the way I use it, I think, after reading your last
post I'm using it wrongly:
First I create it:

       (MySerial*) pMySerial = (MySerial*)
AfxBeginThread( RUNTIME_CLASS( MySerial ), THREAD_PRIORITY_NORMAL, 0,
CREATE_SUSPENDED );

Then I resume it and call OpenPort:

        pMySerial->ResumeThread();
        pMySerial->openPort( port_number );

This activates the ReaderThread automatically.
Then whenever I want send some data through serial port:

       pMySerial->PostThreadMessage( WM_MYSERIAL_WRITE, buffer,
length );

And finally, when I want to close the port and let it ready for
another future open:

      pMySerial->PostThreadMessage( WM_MYSERIAL_CLOSE, 0, 0);

I think I'm doing bad using pMySerial->openPort() directly, instead of
calling it from a message.

Steps 1 and 2 are correct, but not 3. First, PostQuitMessage is used only
with message driven threads (your writer thread). And, it must be called
from the thread that is quitting. You should call it in your writer thread
when it detects the shutdown message/event.

Is every new message sended to MySerial creating a new Thread? I
though that MySerial is a single thread that manages the messages I'm
sending to it.