The question is very general. So what exactly is the problem you cannot solve, and what have you coded so far?

@maxime.armand Have you actually tried it? It does exactly what you demand in step 1. And if you look in http://doc.qt.io/qt-5/qtserialport-creaderasync-main-cpp.html you will see that the serial port and the baud rate are given as command line parameters. Just (cross-)compile the program for the Raspberry, and run it. It should work like your HypterTerminal test.

you can send the string to other class by simply placing it in the Signal, and catch the signal at the other class.

@mrjj as i told you in the thread, it looks the same as on your picture. But it should be transparent, so you can see the code lines from the editor below in your case. But let's continue that in the other thread

@SGaist I edited, thanks

I solved my problem by using this line: if(tmp=="PassDialog") { //QLabel* lbl = f->findChild<QLabel*>("lblRFID"); MyDialog *tempDialog = qobject_cast<MyDialog*>(f); tempDialog->AcceptCard(output); // emit recRFID(output); return; } and clean that connection and comment the emit code. now its worked. But I don't know why that code has error.

@tomasz3dk Wielkie dzięki, pomogło :)