Arduino analog input to QT Gauge.

[StevieGardiner]

And by classes you mean "dialog" when I should be connecting " updatedoilpress"?
And instead of "Rectangle" I should be connecting Rotation"?

Also would this QObject::Connect be the easiest and simplest way of connecting a C++ signal (analogread2, oil_press_bar) to a QML Slot (Neeedle, needleAngle)?

[SGaist]

You'd have to search for the objects you are interest in in your engine and then connect them.

By the way, why not make this dialog also with QtQuick ?

[StevieGardiner]

Ok so id search for the instances, I can google how to do that.

What are the benefits of using QtQuick, over my method?

[SGaist]

That was just curiosity. Nothing wrong in mixing both. If you go with a QtQuick only GUI you should be able to drop the dependency on the QtWidgets module which makes your application lighter weight.

[StevieGardiner]

Hi,

I took your advice and used the cpp for serial data collection and the qml for the GUI, but I'm having a problem with this error.

C:\Users\Stephn\Documents\nissan300zx\serialport.h:50: error: 'double SerialPort::oil_pressure_volt' conflicts with a previous declaration
double oil_pressure_volt;
^

I know that the code is duplicating names, but id like to read that name in Q_Property and then send it to QML.

#ifndef SERIALPORT_H
#define SERIALPORT_H

#include <QObject>
#include <QQuickItem>
#include <QSerialPort>
#include <QSerialPortInfo>
#include <QByteArray>

class SerialPort : public QObject
{
    Q_OBJECT
    Q_PROPERTY(QString oil_pressure_volt READ oil_pressure_volt WRITE set_oil_pressure_volt NOTIFY oil_pressure_volt_Changed)

public:
    SerialPort(QObject *parent = 0);
            SerialPort(QString);


            QString oil_pressure_volt() const
            {
                return m_oil_pressure_volt;
            }

public slots:
    void analogRead2();
    void updateOilPressure(QString);


    void set_oil_pressure_volt(QString oil_pressure_volt)
    {
        if (m_oil_pressure_volt == oil_pressure_volt)
            return;

        m_oil_pressure_volt = oil_pressure_volt;
        emit oil_pressure_volt_Changed(oil_pressure_volt);
    }

signals:

    void oil_pressure_volt_Changed(QString oil_pressure_volt);

private:
    QSerialPort *arduino;
    static const quint16 arduino_uno_vendor_id = 0x2341;
    static const quint16 arduino_uno_product_id = 0x0001;
    QByteArray serialData;
    QString serialBuffer;
    QString parsed_data;
    double oil_pressure_volt;

    QString m_oil_pressure_volt;
};

#endif // SERIALPORT_H

Could I rename the oil_pressure_volt in the CPP

void SerialPort::updateOilPressure(QString sensor_reading)
{
    //oil_pressure_volt(double) = data;

}

[SGaist]

Why are you declaring a oil_pressure_volt property QString then the matching variable as double and still use QString everywhere ?

[StevieGardiner]

Sorry, that was me trying different ideas out.

#ifndef SERIALPORT_H
#define SERIALPORT_H

#include <QObject>
#include <QQuickItem>
#include <QSerialPort>
#include <QSerialPortInfo>
#include <QByteArray>

class SerialPort : public QObject
{
    Q_OBJECT
    Q_PROPERTY(double oil_pressure_volt READ oil_pressure_volt WRITE set_oil_pressure_volt NOTIFY oil_pressure_volt_Changed)

public:
    SerialPort(QObject *parent = 0);
            SerialPort(QString);

            double oil_pressure_volt() const
            {
                return m_oil_pressure_volt;
            }

public slots:
    void analogRead2();
    void updateOilPressure(QString);

    void set_oil_pressure_volt(double oil_pressure_volt)
    {
        if (m_oil_pressure_volt == oil_pressure_volt)
            return;

        m_oil_pressure_volt = oil_pressure_volt;
        emit oil_pressure_volt_Changed(oil_pressure_volt);
    }

signals:

    void oil_pressure_volt_Changed(double oil_pressure_volt);

private:
    QSerialPort *arduino;
    static const quint16 arduino_uno_vendor_id = 0x2341;
    static const quint16 arduino_uno_product_id = 0x0001;
    QByteArray serialData;
    QString serialBuffer;
    QString parsed_data;
    double oil_pressure_volt;

    double m_oil_pressure_volt;
};

#endif // SERIALPORT_H

This is the error,

C:\Users\Stephn\Documents\nissan300zx\serialport.h:48: error: 'double SerialPort::oil_pressure_volt' conflicts with a previous declaration
     double oil_pressure_volt;
            ^

[StevieGardiner]

Hi, So after making a few suggested changes I cant now display a "0" on my qml text field, I think this zero is the first reading of the analogRead 2.

I changed to this in the main.

engine.rootContext()->setContextProperty("serialport", &serialport);

and this in the header.

Q_PROPERTY( double oilPressureVoltage MEMBER m_oil_pressure_volt WRITE set_oil_pressure_volt NOTIFY oil_pressure_volt_Changed )

I think I need to add some code into a string,

#ifndef SERIALPORT_H
#define SERIALPORT_H

#include <QObject>
#include <QQuickItem>
#include <QSerialPort>
#include <QSerialPortInfo>
#include <QByteArray>

class SerialPort : public QObject
{
    Q_OBJECT
    Q_PROPERTY( double oilPressureVoltage MEMBER m_oil_pressure_volt WRITE set_oil_pressure_volt NOTIFY oil_pressure_volt_Changed )

public:
    SerialPort(QObject *parent = 0);
            SerialPort(QString);

public slots:
    void analogRead2();
    void updateOilPressure(QString);

    void set_oil_pressure_volt(double oilPressureVoltage)
    {
        if (m_oilPressureVoltage == oilPressureVoltage)
            return;

        m_oilPressureVoltage = oilPressureVoltage;
        emit oil_pressure_volt_Changed(oilPressureVoltage);
    }

signals:

    void oil_pressure_volt_Changed(double oilPressureVoltage);

private:
    QSerialPort *arduino;
    static const quint16 arduino_uno_vendor_id = 0x2341;
    static const quint16 arduino_uno_product_id = 0x0001;
    QByteArray serialData;
    QString serialBuffer;
    QString parsed_data;
    double oil_pressure_volt;
    double m_oilPressureVoltage;
};

#endif // SERIALPORT_H

[SGaist]

Can you how how you are using that class in QML ?

[StevieGardiner]

yes its...

import QtQuick 2.5
import QtQuick.Window 2.2
import QtQuick.Extras 1.4
import QtQuick.Controls 2.0
import SerialPortlib 1.0

Window {
    id: gauge
    visible: true
    width: 640
    height: 480

    TextEdit {
        id: textEdit
        text: SerialPort.newValue
        verticalAlignment: Text.AlignVCenter
        horizontalAlignment: Text.AlignCenter
        }
}

and...

int main(int argc, char *argv[])
{
QGuiApplication app(argc, argv);
SerialPort serialport;
qmlRegisterType<SerialPort>("SerialPortlib", 1, 0, "SerialPort");
QQmlApplicationEngine engine;
engine.load(QUrl(QStringLiteral("qrc:/main.qml")));

return app.exec();

[SGaist]

What's that newValue ?

You seem to be trying to use a SerialPort object but you are currently accessing it's class (or Type in QML).

You either need to create a SerialPort object in QML or give an instance from it to the engine.

Did you already read the QML CPP integration chapter of Qt's documentation ?

[StevieGardiner]

I tried to create an object by doing;

import QtQuick 2.5
import QtQuick.Window 2.2
import QtQuick.Extras 1.4
import QtQuick.Controls 2.0
import SerialPortlib 1.0

Window {
    visible: true
    width: 640
    height: 480
    id: gauge

    SerialPort{
        OnOil_pressure_volt_Changed:(console.log(newValue));
    }
}

with no joy, is this what your referring too?

[SGaist]

Your QML slot name is wrong.

AFAIK it should be onOil_pressure_volt_changed Note that Qt's naming style is camelCase, that might help you match your code with the documentation.

You should maybe take a look at http://qmlbook.org

[StevieGardiner]

Ahh thank you, that was an interesting read, ive achieved what I wanted.

[SGaist]

Great !

In that case, please mark the thread as solved using the "Topic Tools" button so that other forum users may know a solution has been found :)