Quote Originally Posted by high_flyer View Post
did I misunderstand?
Not certainly in that way.
In fact, device->open()/close() is just the emission of a signal. I emit a signal switchStateSig, then the slot switchState in the thread of the device is called. I do not control this, I just go further in the thread of the algorithm.
I can not call directly, because the device and the algorithm are in different threads, so I had to connect them with a signal and a slot.
This should work like this: from the thread of the algorithm, I call the open/close of the device, I wait for an answer, and only then I go further. Now I just emit a signal and, without waiting for an answer, I go forward. This is very bad. This is the first problem.

The second problem is that the function waitForReadyRead() unpredictably breaks the whole program. I tried to do this, but I did not get a single byte. Apparently, something is blocked:
Qt Code: 
  1. void ms_delay(int ms){
  2.     QElapsedTimer ms_timer;
  3.     ms_timer.start();
  4.     while(ms_timer.elapsed() < ms){}
  5.     return;
  6. }
  7.  
  8. QByteArray ComPort::requestResponse(const QByteArray &data)
  9. {
  10.     mutex->lock();
  11.     qDebug() << "-------------------------";
  12.     if(!serial->isOpen())
  13.         open();
  14.     int attempts = 1;
  15.     QElapsedTimer waitTimer;
  16.     readBuf.clear();
  17.     while (attempts <= 3) {
  18.         if (serial->isWritable())
  19.         {
  20.             serial->write(data);
  21.             waitTimer.restart();
  22.             while (waitTimer.elapsed() < 333){
  23.                 ms_delay(5);
  24.                 readBuf += serial->readAll();
  25.                 if (readBuf.size() == 4){
  26.                     close();
  27.                     mutex->unlock();
  28.                     return readBuf;
  29.                 }
  30.             }
  31.             readBuf.clear();
  32.             qDebug() << "Timeout...";
  33.             close();
  34.             open();
  35.             attempts++;
  36.         }
  37.         else
  38.         {
  39.             qDebug() << "Port is not written";
  40.             close();
  41.             mutex->unlock();
  42.             return 0;
  43.         }
  44.  
  45.     }
  46.     close();
  47.     mutex->unlock();
  48.     return 0;
  49. }
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