Qt first project

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.

nick784512

I have tried this one: https://www.youtube.com/watch?v=UD78xyKbrfk
and I connected the arduino to the COM3 with a program that sends 2 3 2 3... but the Qt program does not display the 2 3 2 3 ....

mrjj

@nick784512
In that video, he mere set the text he gets to a QLabel
MainWindow::serialReceived .
If it should respond to anything you must program it yourself.

Please show what you changed it into to reply ? :)

nick784512

$$$$$$$$$$$$$$$serialGui.pro$$$$$$$$$$$$$$$$$$

#-------------------------------------------------

Project created by QtCreator 2016-12-06T15:42:10

#-------------------------------------------------

QT += core gui serialport

greaterThan(QT_MAJOR_VERSION, 4): QT += widgets

TARGET = serialGui
TEMPLATE = app

SOURCES += main.cpp
mainwindow.cpp

HEADERS += mainwindow.h

FORMS += mainwindow.ui

$$$$$$$$$$$$$$$$$$mainwindow.h$$$$$$$$$$$$$$$$$$$$$$$$$

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>

namespace Ui {
class MainWindow;
}

class MainWindow : public QMainWindow
{
Q_OBJECT

public:
explicit MainWindow(QWidget *parent = 0);
~MainWindow();

private slots:
void serialReceived();

private:
Ui::MainWindow *ui;
};

#endif // MAINWINDOW_H

$$$$$$$$$$$$$$$$$$$$main.cpp$$$$$$$$$$$$$$$$$$$$$$$$$$$

#include "mainwindow.h"
#include <QApplication>

int main(int argc, char *argv[])
{
QApplication a(argc, argv);
MainWindow w;
w.show();

return a.exec();

}

$$$$$$$$$$$$$$$$$$$mainwindow.cpp$$$$$$$$$$$$$$$$$$$$$$$

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <QtSerialPort>
#include <QDebug>

QSerialPort *serial;

MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
serial = new QSerialPort(this);
serial->setPortName("COM3");
serial->setBaudRate(QSerialPort::Baud9600);
serial->setDataBits(QSerialPort::Data8);
serial->setParity(QSerialPort::NoParity);
serial->setStopBits(QSerialPort::OneStop);
serial->setFlowControl(QSerialPort::NoFlowControl);
serial->open(QIODevice::ReadWrite);
serial->write("hello");
serial->close();
connect(serial,SIGNAL(readyRead()),this,SLOT(serialReceived()));
}

MainWindow::~MainWindow()
{
delete ui;
serial->close();
}

void MainWindow::serialReceived()
{
QByteArray ba;
ba=serial->readAll();
ui->label->setText(ba);
qDebug()<<ba;
}

$$$$$$$$$$$$$$$$mainwindow.ui$$$$$$$$$$$$$$$$$$$$$$$$$

<?xml version="1.0" encoding="UTF-8"?>
<ui version="4.0">
<class>MainWindow</class>
<widget class="QMainWindow" name="MainWindow">
<property name="geometry">
<rect>
<x>0</x>
<y>0</y>
<width>400</width>
<height>300</height>
</rect>
</property>
<property name="windowTitle">
<string>MainWindow</string>
</property>
<widget class="QWidget" name="centralWidget">
<widget class="QLabel" name="label">
<property name="geometry">
<rect>
<x>50</x>
<y>60</y>
<width>121</width>
<height>41</height>
</rect>
</property>
<property name="text">
<string>TextLabel</string>
</property>
</widget>
</widget>
<widget class="QMenuBar" name="menuBar">
<property name="geometry">
<rect>
<x>0</x>
<y>0</y>
<width>400</width>
<height>21</height>
</rect>
</property>
</widget>
<widget class="QToolBar" name="mainToolBar">
<attribute name="toolBarArea">
<enum>TopToolBarArea</enum>
</attribute>
<attribute name="toolBarBreak">
<bool>false</bool>
</attribute>
</widget>
<widget class="QStatusBar" name="statusBar"/>
</widget>
<layoutdefault spacing="6" margin="11"/>
<resources/>
<connections/>
</ui>

SGaist

Why are you closing your serial port in the constructor ? You won't receive anything doing so.

nick784512

@SGaist

I disabled it. Again, nothing received.

SGaist

You also don't check whether open was successful.

You should rather move the call to write outside the constructor. e.g. in a slot connected to a push button.

And make serial a member of MainWindow.