Qt first project

nick784512

Hello, I want to build an application that will have a simple button and when I press it to send the command "START" through COM. I am looking the Blocking Master Example but I cannot find the .ui file in order to see how they have programmed the buttons. Any ideas???

mrjj

@nick784512
Hi
Just Select File -> New Project -> Desktop Widget application
in this new project goto Form and click the mainwindow Ui file
Then drag a button from ~~right~~ left to the design area (main window)
Right click the button and select goto Slot
Select the "released()" signal from the list
You should now be in the code showing a slot for the button.
This code is called when button is clicked.

nick784512

Hi, thank you. And which part of Blocking Master Example code do I choose to put inside the brackets of button released?

mrjj

@nick784512
The part you want to call when button is pushed.
In the sample, Dialog.cpp is the window. There is no UI file.

It calls
void Dialog::transaction()

But the real work in done is MasterThread.
So you cannot just put it into the button click.

If you are trying something simple,
this sample is maybe a bit complex to start with
using a thread with more.

To just open a comport and write "start", all you need it.
(Note. you should add more error checking code.)

so if you put in slot

QSerialPort serial;
serial.setPortName("com1");
serial.open(QIODevice::ReadWrite);
serial.setBaudRate(QSerialPort::Baud115200); // MAKE SURE ITS CORRECT
serial.setDataBits(QSerialPort::Data8); // MAKE SURE ITS CORRECT
serial.setParity(QSerialPort::NoParity); // MAKE SURE ITS CORRECT
serial.setStopBits(QSerialPort::OneStop); // MAKE SURE ITS CORRECT
serial.setFlowControl(QSerialPort::HardwareControl); // MAKE SURE ITS CORRECT

if (serial.isOpen() && serial.isWritable())
{
 qDebug() << "Serial is open";
  output = "START";
  serial.write(output);
  serial.waitForBytesWritten(1000);
qDebug() << "sent";
}

if you need a design where "the other end" answers, QSerialPort serial should live as member
of mainwindow.

Btw:
this sample
http://doc.qt.io/qt-5/qtserialport-terminal-example.html
Can send text and show what comes back. its super for testing.

nick784512

Thank you. What version of C++ does the Qt use? It is the "classic" C++ or C++11?

mrjj

@nick784512
Both. I think from 5.7 it must be c++11 but 5.6 LTS can be build with pre c++11.
https://blog.qt.io/blog/2015/12/18/introducing-long-term-support/

nick784512

Hello, Can someone send me a Qt program with one button that when I press it, it sends the command "START" through COM ? I am trying to figure out from Qt examples, but the more I read the more I am confused.

SGaist

Hi,

What exactly is confusing you ?

nick784512

The "terminal" example has so many functions, but too little explanation. How am I supposed to learn how it works, and what functions to use in my simple program (see above)?

SGaist

Do you mean explanation are missing from here ?

nick784512

If you try to read all the files ( that are below )of the example, the explanation is too little.

SGaist

Too little about what ? The key functions are explained in the presentation page and the rest is rather nicely written. So please be more specific about which part is giving you a hard time.

nick784512

What this http://doc.qt.io/qt-5/qtserialport-terminal-settingsdialog-cpp.html code does?
From C language I know that we have to also call a function. Where are the functions called?

SGaist

The dialog is shown when clicking on the configure button in main dialog.

Then when you click on the connect button, the openSerialPort method will retrieve the current setting for the serial port and update the serial member variable properties with the settings from the dialog.

nick784512

Thank you. Now that I want to make the simple project as I said before. How many files do I need?

mainwindow.h
mainwindow.cpp
main.cpp
mainwindow.ui

are all these enough?

SGaist

Based on your requirements, you only need a QWidget, a QPushButton and a QVBoxLayout to put the button nicely in the widget.

nick784512

But where will I put the code?

SGaist

In your QWidget subclass.

nick784512

In main.cpp?

jsulm

@nick784512 I would suggest you to create a simple widgets application and play a bit with it. You will see how Qt widgets applications are usually implemented. See http://doc.qt.io/qtcreator/creator-writing-program.html
Asking others to send you an implementation is not really the right way to learn. Best is "learning by doing" and asking specific questions if you're stuck.