Qt first project

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.

nick784512

Thank you! I cannot understand how the tutorial video in youtube works and the same configuration and coding in my project does not work.

SGaist

Did you check that the settings of the serial ports are really what you need to use with your device ?

nick784512

@SGaist

1)How do I check if the serial opened succefully?
2)I disabled write.
3)Do you mean to make it private member of MainWindow?

SGaist

Please read the documentation, the open function returns a boolean value saying whether it succeeded or not
Where did you put the call to write ?
Yes

nick784512

@SGaist

1)Ok, I will try it.
2)I just commented it.
3) I wrote QSerialPort *serial; under private and it shows error

SGaist

What error ?

If you comment the call to write then don't expect anything particular to happen.

nick784512

@SGaist

C:\Users\geo\Documents\serialGui\mainwindow.h:27: error: 'QSerialPort' does not name a type
QSerialPort *serial;
^

I don't want to write something in COM from Qt, I want to "listen" from Arduino the sequence 232323... and print on the Qt application

SGaist

It's nothing Qt related, that's basic C++. You really should grab a good book on the matter.

Search for "Forward declaration".

nick784512

I know C, not C++. Are they so different?

SGaist

There are some key concepts that are pretty different yes.

nick784512

And I should learn C++ for just this little error?

Can someone help me to make it work?

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();

void on_pushButton_released();

private:
Ui::MainWindow *ui;

QSerialPort *serial;

};

#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)
{
if (serial->open(QIODevice::ReadWrite))
{
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()));
}
else
{
QMessageBox::critical(this, tr("Error"), serial->errorString());
showStatusMessage(tr("Open error"));
}
}

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>

JKSH

@nick784512 said in Qt first project:

And I should learn C++ for just this little error?

You should learn C++ to use a C++ toolkit.

It feels like a "little error" now, but you will encounter this in most (if not all) of your C++ projects.

Can someone help me to make it work?

@SGaist already gave you the answer: You need to add a Forward Declaration for QSerialPort in mainwindow.h.

Also remember to #include <QSerialPort> in mainwindow.cpp

nick784512

Hello!

I managed to make it work and send symbols over the serial. The problem now is that when I send from the arduino (to Qt application) 2 or 3 symbols it prints them OK! But when I want to send the sentence "Hello World!" it breaks it into pieces and prints them, as you can see in the photo.

http://www.picpaste.com/pics/serial_problem-V7LlwzUC.1483458098.jpg

(Can the moderator attach the photo to this message?)