Qt first project

nick784512

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?)

SGaist

That' why you usually have a protocol to know when you received all the data that are part of a "frame" and only then parse them for further processing.

nick784512

How I do this? I think of using a "flag" that when the Qt application reads it, then prints the sentence. Right? For example "Hello World!#" and when it reads the "#", it prints the "Hello World!". Am I correct?

SGaist

More or less, yes.

You buffer the data you can read when readyRead is emitted and once you find your # you take the amount of data needed from the buffer and do whatever you want with it.

nick784512

For buffer is better to use an array or a data structure? List for example and each node to save a letter? Is there a source code to study?

SGaist

Don't over-engineer it, just use a QByteArray.

nick784512

I use an array with a fixed length that when it become full I read it, or an array with dynamic length?

mrjj

@nick784512
Hi
a ByteArray ( dynamic ) would be the best. :)

void SerialPortReader::handleReadyRead()
{
m_readData.append(m_serialPort->readAll());
...