[SOLVED] How to work with the Serial Port in Qt

8Observer8

Hello

I have problems with the Serial Port.

First problem.
I installed Virtual Serial Port driver. And I created pair COM1-COM2. But my application cannot open the port COM1. I receive this message: "The filename, directory name, or volume label syntax is incorrect"

Second problem.
Okay, the port isn't opened but when I check "m_port.isOpen()" is occur this error:

http://i7.pixs.ru/storage/5/4/8/288png_1750629_13532548.png

Third problem.
When I close the window I receive the run time error.

This is my code.
I've written my own exception:
PortError.h
[CODE]
#ifndef PORTERROR_H
#define PORTERROR_H

#include <stdexcept>
#include <string>

class PortError : public std::runtime_error
{
public:
PortError( const std::string &errorText ) : std::runtime_error( "" )
{
m_message = "Error: " + errorText;
}

virtual ~PortError() throw()
{

}

virtual const char *what() const throw()
{
    return m_message.c_str();
}

std::string getMessage()
{
    return m_message;
}

private:
std::string m_message;
};

#endif // PORTERROR_H
[/CODE]

I use it like this:
[CODE]
void MainWindow::on_startTransmissionButton_clicked()
{
QString text = ui->valueForSendingLineEdit->text();
QByteArray data;
data.append( text );
try {
m_sender->send( data );
} catch ( const PortError &e ) {
QMessageBox::information( this, "Error", QString( e.what() ) );
return;
} catch ( ... ) {
QMessageBox::information( this, "Error", "Error: unknown exception" );
return;
}
}
[/CODE]

[CODE]
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);

try {
    m_sender = new Sender( "COM1" );
} catch ( const PortError &e ) {
    QMessageBox::information( this, "Error", QString( e.what() ) );
} catch ( ... ) {
    QMessageBox::information( this, "Error", "Error: unknown exception" );
}

}
[/CODE]

Sender.h
[CODE]
#ifndef SENDER_H
#define SENDER_H

#include <QSerialPort>
#include <QString>
#include "PortError.h"

class Sender
{
public:
Sender( const QString &portName,
QSerialPort::BaudRate baudRate = QSerialPort::Baud9600,
QSerialPort::DataBits dataBits = QSerialPort::Data8,
QSerialPort::Parity parity = QSerialPort::NoParity,
QSerialPort::StopBits stopBits = QSerialPort::OneStop,
QSerialPort::FlowControl flowControl = QSerialPort::NoFlowControl );

~Sender();

void send( const QByteArray &data ) throw( PortError );

private:
QSerialPort m_port;
QString m_portName;
QSerialPort::BaudRate m_baudRate;
QSerialPort::DataBits m_dataBits;
QSerialPort::Parity m_parity;
QSerialPort::StopBits m_stopBits;
QSerialPort::FlowControl m_flowControl;
};

#endif // SENDER_H
[/CODE]

Sender.cpp
[CODE]
#include "Sender.h"

Sender::Sender(const QString &portName,
QSerialPort::BaudRate baudRate,
QSerialPort::DataBits dataBits,
QSerialPort::Parity parity,
QSerialPort::StopBits stopBits,
QSerialPort::FlowControl flowControl ) :
m_port( portName ),
m_baudRate( baudRate ),
m_dataBits( dataBits ),
m_parity( parity ),
m_stopBits( stopBits ),
m_flowControl( flowControl )
{
// Set the port name
m_port.setPortName( m_portName );

// Open the port
if ( !m_port.open( QIODevice::WriteOnly ) ) {
    throw PortError( m_port.errorString().toStdString() );
}

m_port.setBaudRate( m_baudRate );
m_port.setDataBits( m_dataBits );
m_port.setParity( m_parity );
m_port.setStopBits( m_stopBits );
m_port.setFlowControl( m_flowControl );

}

Sender::~Sender()
{
m_port.close();
}

void Sender::send( const QByteArray &data ) throw( PortError )
{
// Write data to the port
if ( m_port.write( data ) == -1 ) {
throw PortError( m_port.errorString().toStdString() );
}
}
[/CODE]

8Observer8

I delete the m_sender object here:
[CODE]
MainWindow::~MainWindow()
{
delete ui;
delete m_sender;
}
[/CODE]

8Observer8

The main problem: my application crash when I call .isOpen() Method. Why? Who can say the reason?

[CODE]
void Sender::send( const QByteArray &data ) throw( PortError )
{
if ( !m_port.isOpen() ) {
throw PortError( m_port.errorString().toStdString() );
}

// Write data to the port
if ( m_port.write( data ) == -1 ) {
    throw PortError( m_port.errorString().toStdString() );
}

}[/CODE]

P.S. You see that it is very simple application

SGaist

Hi,

Please run your application using a debugger, it will tell you exactly where the code is crashing

8Observer8

I've written. Here: "if ( !m_port.isOpen() )" in my last post. And I see this message:
http://i6.pixs.ru/storage/4/6/9/288png_9391611_13540469.png

SGaist

Indeed, but running with the debugger, it will show you the stack trace and that would be more useful to help finding where the problem is.

8Observer8

I was helped here: [url]http://www.prog.org.ru/index.php?topic=27520[/url]

The error on this line "m_port( portName ),"
[CODE]
Sender::Sender( const QString &portName,
QSerialPort::BaudRate baudRate,
QSerialPort::DataBits dataBits,
QSerialPort::Parity parity,
QSerialPort::StopBits stopBits,
QSerialPort::FlowControl flowControl ) :
m_port( portName ),
m_baudRate( baudRate ),
m_dataBits( dataBits ),
m_parity( parity ),
m_stopBits( stopBits ),
m_flowControl( flowControl )
{
// Set the port name
m_port.setPortName( m_portName );[/CODE]

I should have written m_portName instead m_port.

I replaced "QSerialPort m_port;" on "QSerialPort m_serialPort;" And I delete the m_portName because I can to write m_serialPort( portName ) in the "Sender" constructor.

It is my project: [url]https://github.com/8Observer8/ComPort[/url]

SGaist

Since you are using exceptions, please take a look at the corresponding chapter in Qt's documentation.

8Observer8

Please, show me what do you mean? Cannot I use exceptions?

SGaist

Yes, you can, but there are some rules. Read "this":http://qt-project.org/doc/qt-5/exceptionsafety.html

8Observer8

Thank you very much! :)