SLOT fires only on mouse move

[kartun]

I've this code ... stripped a bit

void testform::keyPressEvent(QKeyEvent *event)
{
    switch (event->key())
    {
        case Qt::Key_4 :
            if (!demo_started)
            {
                this->buttons[0]->setPixmap(QPixmap::fromImage(images[1]));
                this->listener = new PortListener(portName);
 
                // So, connect to listener, and ... all happy :P
                connect(this->listener,SIGNAL(packet_received(data_answer)),
                        this,SLOT(packet_received(data_answer)));
 
            }
            else
            {
                this->buttons[0]->setPixmap(QPixmap::fromImage(images[0]));
                this->killTimer(demo_timer_id)
            }
            demo_started = !demo_started;
            break;
   ...................................
        default : QWidget::keyPressEvent(event);
    }
}

void testform::keyPressEvent(QKeyEvent *event)
{
    switch (event->key())
    {
        case Qt::Key_4 :
            if (!demo_started)
            {
                this->buttons[0]->setPixmap(QPixmap::fromImage(images[1]));
                this->listener = new PortListener(portName);

                // So, connect to listener, and ... all happy :P
                connect(this->listener,SIGNAL(packet_received(data_answer)),
                        this,SLOT(packet_received(data_answer)));

            }
            else
            {
                this->buttons[0]->setPixmap(QPixmap::fromImage(images[0]));
                this->killTimer(demo_timer_id)
            }
            demo_started = !demo_started;
            break;
   ...................................
        default : QWidget::keyPressEvent(event);
    }
}

To copy to clipboard, switch view to plain text mode 

and receiver SLOT:

void testform::packet_received(data_answer answer)
{
    qDebug() << "pewpew all dead !";
    redrawUI();
}

void testform::packet_received(data_answer answer)
{
    qDebug() << "pewpew all dead !";
    redrawUI();
}

To copy to clipboard, switch view to plain text mode 

Problem is that this slot called only when I move mouse,press key etc. But signal itself emmited every 0.5 seconds (read data from com-port). Listener class is quite stable and works as intended.

[high_flyer]

Problem is that this slot called only when I move mouse,press key etc. But signal itself emmited every 0.5 seconds

Do you mean it only starts to be called after you have pressed a key (but then regularly gets called after that), or only when you press a key the slot is called?
Do you use diconnect() in your code anywhere, or delete the listener?

[kartun]

no, no disconnect() anywhere.
I checked with debugger, and even signal doesn't emitted unless I click on window, or press button. And yes, it's emitted only when i push/click.
Listener instance deleted in desctructor.

tryReceive() called in listener constructor first time, and then recalled with floating window.

void PortListener::tryReceive(){
   if(this->port->bytesAvailable()>0){
       timeout = qMax(100, timeout/2);       
       myRcvBuffer.clear();
       myRcvBuffer.append(port->readAll());
       qDebug() << "bytes read:" << myRcvBuffer.length();
       qDebug() << "bytes:" << myRcvBuffer;
       last_packet = Hemofenix_protocol::decode_packet(myRcvBuffer);
       emit packet_received(last_packet);
   } else {
       timeout = qMin(1000, timeout*2);
   }
   QTimer::singleShot(timeout, this, SLOT(tryReceive()));
}

void PortListener::tryReceive(){
   if(this->port->bytesAvailable()>0){
       timeout = qMax(100, timeout/2);       
       myRcvBuffer.clear();
       myRcvBuffer.append(port->readAll());
       qDebug() << "bytes read:" << myRcvBuffer.length();
       qDebug() << "bytes:" << myRcvBuffer;
       last_packet = Hemofenix_protocol::decode_packet(myRcvBuffer);
       emit packet_received(last_packet);
   } else {
       timeout = qMin(1000, timeout*2);
   }
   QTimer::singleShot(timeout, this, SLOT(tryReceive()));
}

To copy to clipboard, switch view to plain text mode 

I put some qDebug() output there, but it do output only on user actions

[high_flyer]

But signal itself emmited every 0.5 seconds

Your posted code does not supports this assertion.
Your packet_received signal is only emitted when bayteAvailble()>0 is true however.
So it seems that for some reason bytesAvalable() returns 0 or less unless you press a key.
This sounds like a busy loop problem somewhere in your code.

[kartun]

Mystics ... I left code untouched for weekend, compiled today and it works like a charm. Really wired.
Thanks for replys.