Arduino serial input qml display text, conflict of previous declaration error.

[StevieGardiner]

Hi Guys,

Ive been working on a project trying to read the analog input from an Arduino board through serial, then display this on a qml gui in text form first and then move onto a rotating gauge.

I completed the process using qdebug at each step, so I'm reading the input until I come to the Q_PROPERTY stage and I get this error.

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

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

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^

#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

#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

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much appreciated for any help you can give me.

[d_stranz]

The Q_PROPERTY macro defines the member variable oil_pressure_volt for you. Line 48 is adding a duplicate definition and thus causing the error. Delete that line. Get rid of m_oil_pressure_volt also, since it is just a duplicate of the property.

You would confuse yourself less if you didn't use the name "oil_pressure_volt" everywhere. C++ doesn't care what the argument names are, so in the set method, use "newValue" or something like that. Likewise in your definition of the signal.

If you want the -name- of the property that is exposed to QML to be something different from the member variable name, then use the MEMBER form of Q_PROPERTY:

Q_PROPERTY( double oilPressureVoltage MEMBER m_oil_pressure_volt WRITE set_oil_pressure_volt NOTIFY oil_pressure_volt_Changed )

Q_PROPERTY( double oilPressureVoltage MEMBER m_oil_pressure_volt WRITE set_oil_pressure_volt NOTIFY oil_pressure_volt_Changed )

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You will refer to it as "oilPressureVoltage" from QML.

[StevieGardiner]

Much appreciated for clarifying that... and after adding your code and trying I still couldn't see anything in the main.qml.

I'm using the "double oil_pressure_volt" in my serialport.cpp code below, it takes my 10 bit analog input and turns it into a voltage reading. Would I be better doing the conversion in the qml?

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

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

    return app.exec();

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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

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

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void SerialPort::analogRead2()
{
    QStringList buffer_split = serialBuffer.split(",");
    if(buffer_split.length() < 3)
    {
        serialData = arduino->readAll();
        serialBuffer = serialBuffer + QString::fromStdString(serialData.toStdString());
        serialData.clear();
    }else{
        serialBuffer = "";
        qDebug() << buffer_split << "\n";
        parsed_data = buffer_split[1];
        oil_pressure_volt = (0.0048) * (parsed_data.toDouble());
        qDebug() << "Pressure: " << oil_pressure_volt << "\n";
    }

void SerialPort::analogRead2()
{
    QStringList buffer_split = serialBuffer.split(",");
    if(buffer_split.length() < 3)
    {
        serialData = arduino->readAll();
        serialBuffer = serialBuffer + QString::fromStdString(serialData.toStdString());
        serialData.clear();
    }else{
        serialBuffer = "";
        qDebug() << buffer_split << "\n";
        parsed_data = buffer_split[1];
        oil_pressure_volt = (0.0048) * (parsed_data.toDouble());
        qDebug() << "Pressure: " << oil_pressure_volt << "\n";
    }

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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     
 
    TextField {
        id: textField
        x: 250
        y: 280
        text: SerialPort.oilPressureVoltage
    }
}

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     

    TextField {
        id: textField
        x: 250
        y: 280
        text: SerialPort.oilPressureVoltage
    }
}

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[Lesiok]

First change line

oil_pressure_volt = (0.0048) * (parsed_data.toDouble());

oil_pressure_volt = (0.0048) * (parsed_data.toDouble());

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to

set_oil_pressure_volt((0.0048) * (parsed_data.toDouble()));

set_oil_pressure_volt((0.0048) * (parsed_data.toDouble()));

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P.S. Try to figure out why.

[StevieGardiner]

Hi Lesiok, thanks for you help, I changed this line with nothing still in the qml.

[StevieGardiner]

An update guys, after changing to this in the main.cpp, I managed to display a "0" which I think is the first reading from the analogRead2, then the rest is the voltage.

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

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

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I would think id need to add this code to a loop, and advice guys is much appreciated.

void set_oil_pressure_volt(double oilPressureVoltage)
    {
        if (m_oilPressureVoltage != oilPressureVoltage)
            return;
 
        m_oilPressureVoltage = oilPressureVoltage;
        emit oil_pressure_volt_Changed(oilPressureVoltage);
    }

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

        m_oilPressureVoltage = oilPressureVoltage;
        emit oil_pressure_volt_Changed(oilPressureVoltage);
    }

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[Lesiok]

How is SerialPort::analogRead2() activated ?

[StevieGardiner]

By the QObject::Connect on line 43

#include "serialport.h"
#include <QSerialPort>
#include <QSerialPortInfo>
#include <string>
#include <QDebug>
#include <QQuickView>
#include <QQmlApplicationEngine>
#include <QApplication>
#include <QtQuickWidgets/QQuickWidget>
 
SerialPort::SerialPort(QObject *parent)
{
    arduino = new QSerialPort(this);
 
    serialBuffer = "";
    parsed_data = "";
    oil_pressure_volt = 0.0;
 
    bool arduino_is_available = false;
    QString arduino_uno_port_name;
 
    foreach(const QSerialPortInfo &serialPortInfo, QSerialPortInfo::availablePorts()){
        //  check if the serialport has both a product identifier and a vendor identifier
        if(serialPortInfo.hasProductIdentifier() && serialPortInfo.hasVendorIdentifier()){
            //  check if the product ID and the vendor ID match those of the arduino uno
            if((serialPortInfo.productIdentifier() == arduino_uno_product_id)
                    && (serialPortInfo.vendorIdentifier() == arduino_uno_vendor_id)){
                arduino_is_available = true; //    arduino uno is available on this port
                arduino_uno_port_name = serialPortInfo.portName();
            }
        }
    }
 
    if(arduino_is_available){
        qDebug() << "Found the arduino port...\n";
        arduino->setPortName(arduino_uno_port_name);
        arduino->open(QSerialPort::ReadOnly);
        arduino->setBaudRate(QSerialPort::Baud57600);
        arduino->setDataBits(QSerialPort::Data8);
        arduino->setFlowControl(QSerialPort::NoFlowControl);
        arduino->setParity(QSerialPort::NoParity);
        arduino->setStopBits(QSerialPort::OneStop);
        QObject::connect(arduino, SIGNAL(readyRead()), this, SLOT(analogRead2()));
 
    }else{
        qDebug() << "Couldn't find the correct port for the arduino.\n";
        //QMessageBox::information(this, "Serial Port Error", "Couldn't open serial port to arduino.");
    }
 
}
void SerialPort::analogRead2()
{
    QStringList buffer_split = serialBuffer.split(",");
    if(buffer_split.length() < 3)
    {
        serialData = arduino->readAll();
        serialBuffer = serialBuffer + QString::fromStdString(serialData.toStdString());
        serialData.clear();
    }else{
        serialBuffer = "";
        qDebug() << buffer_split << "\n";
        parsed_data = buffer_split[1];
        oil_pressure_volt = (0.0048) * (parsed_data.toDouble());
        //set_oil_pressure_volt((0.0048) * (parsed_data.toDouble()));
        qDebug() << "Pressure: " << oil_pressure_volt << "\n";
    }
}
 
void SerialPort::updateOilPressure(QString sensor_reading)
{
 
}

#include "serialport.h"
#include <QSerialPort>
#include <QSerialPortInfo>
#include <string>
#include <QDebug>
#include <QQuickView>
#include <QQmlApplicationEngine>
#include <QApplication>
#include <QtQuickWidgets/QQuickWidget>

SerialPort::SerialPort(QObject *parent)
{
    arduino = new QSerialPort(this);

    serialBuffer = "";
    parsed_data = "";
    oil_pressure_volt = 0.0;

    bool arduino_is_available = false;
    QString arduino_uno_port_name;

    foreach(const QSerialPortInfo &serialPortInfo, QSerialPortInfo::availablePorts()){
        //  check if the serialport has both a product identifier and a vendor identifier
        if(serialPortInfo.hasProductIdentifier() && serialPortInfo.hasVendorIdentifier()){
            //  check if the product ID and the vendor ID match those of the arduino uno
            if((serialPortInfo.productIdentifier() == arduino_uno_product_id)
                    && (serialPortInfo.vendorIdentifier() == arduino_uno_vendor_id)){
                arduino_is_available = true; //    arduino uno is available on this port
                arduino_uno_port_name = serialPortInfo.portName();
            }
        }
    }

    if(arduino_is_available){
        qDebug() << "Found the arduino port...\n";
        arduino->setPortName(arduino_uno_port_name);
        arduino->open(QSerialPort::ReadOnly);
        arduino->setBaudRate(QSerialPort::Baud57600);
        arduino->setDataBits(QSerialPort::Data8);
        arduino->setFlowControl(QSerialPort::NoFlowControl);
        arduino->setParity(QSerialPort::NoParity);
        arduino->setStopBits(QSerialPort::OneStop);
        QObject::connect(arduino, SIGNAL(readyRead()), this, SLOT(analogRead2()));

    }else{
        qDebug() << "Couldn't find the correct port for the arduino.\n";
        //QMessageBox::information(this, "Serial Port Error", "Couldn't open serial port to arduino.");
    }

}
void SerialPort::analogRead2()
{
    QStringList buffer_split = serialBuffer.split(",");
    if(buffer_split.length() < 3)
    {
        serialData = arduino->readAll();
        serialBuffer = serialBuffer + QString::fromStdString(serialData.toStdString());
        serialData.clear();
    }else{
        serialBuffer = "";
        qDebug() << buffer_split << "\n";
        parsed_data = buffer_split[1];
        oil_pressure_volt = (0.0048) * (parsed_data.toDouble());
        //set_oil_pressure_volt((0.0048) * (parsed_data.toDouble()));
        qDebug() << "Pressure: " << oil_pressure_volt << "\n";
    }
}

void SerialPort::updateOilPressure(QString sensor_reading)
{

}

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[Lesiok]

And on qDebug you have a series of messages "Pressure: ...." ?
BTW : I see that you have not figured out why it should be line 64 and not 63. Line 63 changes oil_pressure_volt but not generate signal oil_pressure_volt_Changed.

[StevieGardiner]

Yes on qDebug, this is so I could see the input in *.cpp
I just tried again by applying line 64 and commenting out line 63, and the qml still shows "0"

I think I need to apply a loop somewhere,

[Lesiok]

I'm not using QML so I don't know how to use signal oil_pressure_volt_Changed in QML.