Tried to qdebug the output while the serial port is not open

[sankarapandiyan]

I have tried to qdebug like "SERIAL PORT IS NOT OPEN" like this... i have tried in the code but i cant get a output .

I am tried with same laptop by connecting the two ports , ttyUSB0 and ttyUSB1 .
Here i am removing the ttyUSB1 .. and i tried to send the data . If the serial port (ttyUSB1) is unplugged So, here the serial port is not open ..
so i want to qdebug like "THE PORT IS NOT CONNECTED "
i have tried on inside the function but its not works ..

 void MainWindow ::on_send_clicked()

I have tried like something like this i have attached my code below

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <QList>
#include <QComboBox>
#include <QString>
#include <QTextEdit>
#include <QTime>
#include <QDebug>
#include <QtSerialPort/QSerialPortInfo>
#include <QtSerialPort>
#include <QFile>
#include <QList>

QString line ;
QString txt3;
QSerialPort *serial;
QStringList m_lines;
//QByteArray rawData;


MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
    , ui(new Ui::MainWindow)
{
      ui->setupUi(this);
        QList<QSerialPortInfo> list;
    list = QSerialPortInfo::availablePorts();
    for (int i= 0; i < list.length(); i++)
    {
        ui->comboBox->addItem(list[i].portName());
    }
}

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


void MainWindow::on_pushButton_clicked()
{
    serial = new QSerialPort (this) ;
    serial->setPortName(ui->comboBox->currentText());
    serial->setBaudRate (QSerialPort::Baud115200);
    serial->setDataBits(QSerialPort::Data8);
    serial->setParity (QSerialPort::NoParity);
    serial->setStopBits (QSerialPort::OneStop);
    serial->setFlowControl(QSerialPort::NoFlowControl);
    serial->open(QIODevice::ReadWrite);
    connect(serial,SIGNAL(readyRead()),this, SLOT (serialReceived()));
    ui->progressBar->setValue(100);
//    ui->receive->clear();
}

void MainWindow::checkAndSendData()
{
    if(!m_lines.isEmpty()){
        QByteArray baToSend = m_lines.takeFirst().toUtf8();
        serial->write(baToSend);
        ui->aknowmnt->setText("Sent Message -->" "\n"+  QString(baToSend) + "\n");
    } else {
        ui->aknowmnt->setText("Receiving ");
    }
}

void MainWindow ::on_send_clicked()
{
           if(!serial->open(QIODevice::ReadWrite| QIODevice::Unbuffered)) // Here i have declared ...
            {
                qDebug()<<"error: can't open com port";
                ui->aknowmnt->setText("Port is not opening ");
            }     

        line = ui->sender->toPlainText();
        QString txt1 = ui->receive->toPlainText();
        /*QString*/ txt3 = ui->aknowmnt->toPlainText();
         if(m_lines.isEmpty()){
            QFile inputFile(QString("/home/adx-soft1/Shankar/serial/myfile1.txt"));
            inputFile.open(QIODevice::ReadOnly);
            if (!inputFile.isOpen())
                return;

            QTextStream stream(&inputFile);
            while(!stream.atEnd()){
                QString line = stream.readLine();
                m_lines.append(line + QString("\r\n"));
            }
        }

        checkAndSendData();
}


void MainWindow::serialReceived()
{
    QString glen = serial->readAll();
    if (glen.length()>0){
    /*QString*/ line = ui->receive->toPlainText();
    ui->receive->setText(ui->receive->toPlainText()+line+"\n");
    ui->receive->setText(line + "\r\n" + glen + "\r\n");
   // line = txt3;
    }

    checkAndSendData();
}

[maxwell31]

Are you using Linux? Then you need to check the permissions of ttyUSB0, or generate an appropriate udev rule

[sankarapandiyan]

@maxwell31 YEs i am using Linux only ... But i want to qdebug the port which is "port is not opening ".. while clicking the send button . I write some code for that in the send button . please check it my code is it correct or not thats only i want

[KillerSmath]

@sankarapandiyan

When the device is unplugged, it maybe emits an error signal, so you could handle this signal by connecting a slot on it.

connect(serial, SIGNAL(error(QSerialPort::SerialPortError), this, SLOT(your_slot_function(QSerialPort::SerialPortError));

List of possible results of SerialPortError enum:
https://doc.qt.io/qt-5/qserialport.html#SerialPortError-enum

The type of error that is most similar to the behavior you are trying to achieve is QSerialPort::ResourceError

void MainWindow::your_slot_function(QSerialPort::SerialPortError error)
{
    if (error == QSerialPort::ResourceError)
    {
        qDebug() << "Resource becomes unavailable";
        serial->close(); // close the serial
    }
}

---

As an addition, you could check if the serial is already opened instead of try to open it again inside of on_send_clicked function.

    if(!serial->isOpen()){ // if is not open then try to open
            if(!serial->open(QIODevice::ReadWrite| QIODevice::Unbuffered)){
                qDebug()<<"error: can't open com port";
                ui->aknowmnt->setText("Port is not opening ");
            }   
    }

[sankarapandiyan]

@KillerSmath Yes i tried with this but i did not get it ..
this is my code
the code flow is right or wrong please suggest me ...,

QString line ;
QString txt3;
QSerialPort *serial;
QStringList m_lines;
//QByteArray rawData;


MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
    , ui(new Ui::MainWindow)
{

      ui->setupUi(this);

      QString filename1="/home/adx-soft1/Shankar/serial/myfile1.txt";
      QFile file(filename1);
      if(!file.exists()){
          qDebug() << "NO FILE "<<filename1;
      }else{
          qDebug() << filename1<<" ...";
      }
      QString line1;
      ui->sender->clear();
      if (file.open(QIODevice::ReadOnly | QIODevice::Text)){ ui->sender->setText(file.readAll()); }

    QList<QSerialPortInfo> list;
    list = QSerialPortInfo::availablePorts();

    for (int i= 0; i < list.length(); i++)
    {
        ui->comboBox->addItem(list[i].portName());

    }
}

MainWindow::~MainWindow()
{
    delete ui;
    serial->close();
}
void MainWindow::your_slot_function(QSerialPort::SerialPortError error)
{
    if (error == QSerialPort::ResourceError)
    {
        qDebug() << "Resource becomes unavailable";
        ui->aknowmnt->setText("PORT IS NOT OPENING");
        serial->close(); // close the serial
    }
}

void MainWindow::on_pushButton_clicked()
{
    serial = new QSerialPort (this) ;
    serial->setPortName(ui->comboBox->currentText());
    serial->setBaudRate (QSerialPort::Baud115200);
    serial->setDataBits(QSerialPort::Data8);
    serial->setParity (QSerialPort::NoParity);
    serial->setStopBits (QSerialPort::OneStop);
    serial->setFlowControl(QSerialPort::NoFlowControl);
    serial->open(QIODevice::ReadWrite);
   connect(serial,SIGNAL(readyRead()),this, SLOT (serialReceived()));
   connect(serial,SIGNAL(QSerialPort::SerialPortError), this, SLOT(your_slot_function(QSerialPort::SerialPortError)));

//    if(!serial->open(QIODevice::ReadWrite| QIODevice::Unbuffered))
//    {
//        qDebug()<<"error: can't open com port";
//        ui->aknowmnt->setText("Port is not opening ");
//    }

   ui->progressBar->setValue(100);
//    ui->receive->clear();
}
void MainWindow::checkAndSendData()
{
    if (!serial->isOpen())
     {
        qDebug()<<"error: can't open com port";
        ui->aknowmnt->setText("device is not open  ");
         //Port not open

     }
    if(!m_lines.isEmpty()){
        QByteArray baToSend = m_lines.takeFirst().toUtf8();
        serial->write(baToSend);
        ui->aknowmnt->setText("Sent Message -->" "\n"+  QString(baToSend) + "\n");
    }
    else
    {
        ui->aknowmnt->setText("Receiving ");
    }

}


void MainWindow ::on_send_clicked()
{
        line = ui->sender->toPlainText();
        QString txt1 = ui->receive->toPlainText();
        /*QString*/ txt3 = ui->aknowmnt->toPlainText();
         if(m_lines.isEmpty()){
            QFile inputFile(QString("/home/adx-soft1/Shankar/serial/myfile1.txt"));
            inputFile.open(QIODevice::ReadOnly);
            if (!inputFile.isOpen())
                return;

            QTextStream stream(&inputFile);
            while(!stream.atEnd()){
                QString line = stream.readLine();
                m_lines.append(line + QString("\r\n"));
            }
        }

        checkAndSendData();
}


void MainWindow::serialReceived()
{
    QString glen = serial->readAll();
    if (glen.length()>0){
    /*QString*/ line = ui->receive->toPlainText();
    ui->receive->setText(ui->receive->toPlainText()+line+"\n");
    ui->receive->setText(line + "\r\n" + glen + "\r\n");
   // line = txt3;
    }

    checkAndSendData();
}

[maxwell31]

What I want to say: As a user you don't have access to ttyUSB0. You should either chmod 777 /dev/ttyUSB0 (just for checking, after a reboot it will be reset), create a udev rule for usb (see https://askubuntu.com/questions/15570/configure-udev-to-change-permissions-on-usb-hid-device) or for quick testing if permissions are the reason, you can also start your program with sudo.

[Christian Ehrlicher]

@maxwell31 said in Tried to qdebug the output while the serial port is not open:

As a user you don't have access to ttyUSB0

Why? You just have to be in the group dialout. Using chmod or running as root is a hack.

[sankarapandiyan]

@Christian-Ehrlicher said in Tried to qdebug the output while the serial port is not open:

You just have to be in the group dialout.

Yes i have done like this only.

[sankarapandiyan]

@maxwell31 ok i will try