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

[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.

[StevieGardiner]

No worries mate, thank you for helping.

[d_stranz]

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

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

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As with Lesiok, I'm not a QML expert either, but doesn't a TextField expect to receive a string type for the value of its "text" property? You're assigning a double to it. If it doesn't do an automatic type conversion of double to a printable representation (i.e. a string), then that could be where your unchanging "0" comes from.

You could test this by hard-coding a value on your C++ side (e.g. fix m_oilPressureVoltage at some known value and never change it, but continue to emit the signals as if you had). If you don't see -your- value on the QML side, then either the type conversion isn't happening or the signal still isn't getting picked up.

P. S. I see you're still confusing yourself by reusing the same names for variables all over the place. The name of the argument in your definition of set_oil_pressure_volt does not have to be the same as the property name. Use something different and unique (like "newVoltage") so when you look at the name "oilPressureVoltage" you know immediately it refers to the symbolic name of the Q_PROPERTY. Likewise, "newVoltage" only appears as the name of an argument to a class method and nowhere else, so it can't be confused either.

You may think this ridiculously pedantic, but from long experience I can tell you that if you need to go back to this code sometime later, you'll be thankful you chose unique, non-reused names because the first thing you'll have to do is re-learn what the code does because you'll have forgotten. It also can help you avoid days of debugging when you decide to rename something and the find and replace does -all- of them, including the ones it shouldn't have.

[StevieGardiner]

Hi Gents,

I tried with this with no joy,

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_Changedconsole.log(newValue));
}
}

[d_stranz]

Sorry, but not knowing much QML beyond the basics, I don't have a clue what this code is supposed to do, or even if it is correct. C++, fine, but I have not yet made the treacherous crossing over into QMLandia and confronted the formidable beasts that dwell there.

It should be dead simple for you to implement a basic and purely C++ GUI for testing purposes. It eliminates one significant variable from the mix - get the communications working in C++, then map that GUI onto QML.