How to Save Continued Data received by device during serial communication?

[segtteee]

I am doing serial communication with the equipment. If i set up the port, press on the monitor and connect button , connect pc and device. I have been receiving continuous data from the equipment and tried to save it as txt (numeric) implementation. However, when I run the code I wrote, only the last value is written in the txt file. I want to record all of the ongoing data. What should I do?

below is total my code.

#include "mainwindow.h"
#include "ui_mainwindow.h"

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
    mSerialport = new QSerialPort (this);
    connect(mSerialport,SIGNAL(readyRead()),this,SLOT(read_device_data()));

    connect(ui->radioButton_on,SIGNAL(clicked(bool)),this,SLOT(on_radioButton_on_clicked()));

    connect(ui->radioButton_off,SIGNAL(clicked(bool)),this,SLOT(on_radioButton_off_clicked()));
}

MainWindow::~MainWindow()
{
    delete ui;
}

void MainWindow::on_pushButton_connect_clicked()
{
    mSerialport->setPortName(ui->comboBox_port->currentText());

    if (ui->comboBox_baudrate->currentText() == "9600 bps")
        mSerialport->setBaudRate(QSerialPort::Baud9600);
    else if (ui->comboBox_baudrate->currentText() == "19200 bps")
        mSerialport->setBaudRate(QSerialPort::Baud19200);
    else if (ui->comboBox_baudrate->currentText() == "38400 bps")
        mSerialport->setBaudRate(QSerialPort::Baud38400);
    else if (ui->comboBox_baudrate->currentText() == "57600 bps")
        mSerialport->setBaudRate(QSerialPort::Baud57600);
    else if (ui->comboBox_baudrate->currentText() == "115200 bps")
        mSerialport->setBaudRate(QSerialPort::Baud115200);

    mSerialport->setDataBits(QSerialPort::Data8);
    mSerialport->setStopBits(QSerialPort::OneStop);

    if (mSerialport->open(QIODevice::ReadWrite))
    {
        QMessageBox::information(this,tr("connect"),"Serial communication start");
    }
    else
    {
        QMessageBox::critical(this,tr("error"),mSerialport->errorString());
    }
}

void MainWindow::on_pushButton_disconnect_clicked()
{
    QMessageBox::information(this,tr("disconnect"),"Serial communication end");
    mSerialport->close();
}

void MainWindow::read_device_data()
{
    QByteArray device_data(mSerialport->readAll());
    ui->data_show->setText(device_data);

    QFile file("/home/mycdc/datasave.txt");
    if(file.open(QIODevice::WriteOnly)){
        file.write(device_data);
        
        file.close();
    }

    double number = QString(device_data).remove('\n').toDouble() * 1000;
    qDebug() << number;
    ui->dial->setValue(number);
}

void MainWindow::on_radioButton_on_clicked()
{
    qDebug() << "written->" << mSerialport->write("mon 1\n");
}

void MainWindow::on_radioButton_off_clicked()
{
    qDebug() << "written->" << mSerialport->write("mon 0\n");
}

Here is where I implemented the data storage

void MainWindow::read_device_data()
{
    QByteArray device_data(mSerialport->readAll());
    ui->data_show->setText(device_data);

    QFile file("/home/mycdc/datasave.txt");
    if(file.open(QIODevice::WriteOnly)){
        file.write(device_data);
        
        file.close();
    }

    double number = QString(device_data).remove('\n').toDouble() * 1000;
    qDebug() << number;
    ui->dial->setValue(number);
}

[jsulm]

@segtteee That' because you overwrite the file each time you open it. You need to use

if(file.open(QIODevice::WriteOnly | QIODevice::Text | QIODevice::Append)){

QIODevice::Append - to append to the file (default is to overwrite).
QIODevice::Text - you said you want to write text file.
Explained here: http://doc.qt.io/qt-5/qiodevice.html#OpenModeFlag-enum

[segtteee]

@jsulm
Thanks. I solved the problem. :D