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 :)