How to send the Data from Qt App to Arduino by serial communication

sankarapandiyan

I have tried to send the data from Qt app to Arduino and i want to display the Received data in the serial monitor (Arduin IDE)
In Qt , i have develop some code to sending the data stored in the text file ,
THIS IS THE CODE..

void MainWindow::on_pushButton_clicked()
{
    serial = new QSerialPort (this) ;
    serial->setPortName(ui->comboBox->currentText());
    serial->setBaudRate (QSerialPort::Baud9600);
    serial->setDataBits(QSerialPort::Data8);
    serial->setParity (QSerialPort::NoParity);
    serial->setStopBits (QSerialPort::OneStop);
    serial->setFlowControl(QSerialPort::NoFlowControl);
    serial->open(QIODevice::ReadWrite);
   connect(serial,SIGNAL(readyRead()),this, SLOT (serialReceived()));

   ui->progressBar->setValue(100);
//    ui->receive->clear();
}
void MainWindow::checkAndSendData()
{
    if(!m_lines.isEmpty()){
        QByteArray baToSend = m_lines.takeFirst().toUtf8();
        serial->write(baToSend);
        ui->aknowmnt->setText("Sent Message -->" +  QString(baToSend) + "\n");
    }
    else
    {
        ui->aknowmnt->setText("Receiving ");
    }
}


void MainWindow ::on_send_clicked()
{
        line = ui->sender->toPlainText();
        QString txt1 = ui->receive->toPlainText();
        /*QString*/ txt3 = ui->aknowmnt->toPlainText();
         if(m_lines.isEmpty()){
            QFile inputFile(QString("/home/adx-soft1/Shankar/serial/myfile1.txt"));
            inputFile.open(QIODevice::ReadOnly);
            if (!inputFile.isOpen())
                return;

            QTextStream stream(&inputFile);
            while(!stream.atEnd()){
                QString line = stream.readLine();
                m_lines.append(line + QString("\r\n"));
            }
        }

        checkAndSendData();
}

And i have develop the code in Aurdino IDE also ,

int incomingByte = 0; // for incoming serial data

void setup() {
  Serial.begin(9600); // opens serial port, sets data rate to 9600 bps
}

void loop() {
  // reply only when you receive data:
  if (Serial.available() > 0) {
    // read the incoming byte:
    incomingByte = Serial.read();

    // say what you got:
    Serial.print("I received: ");
    Serial.println(incomingByte, DEC);
  }
}

If i Clicked the send button .. I am not able to see the data Received in Arduino . And i want to show the Received data in the Serial monitor , And i am new to this topic (ARDUINO-SERIAL-PORT-COMMUNICATION-QT)
I think I need to modify the Aurdino IDE Code ,
Please say me some suggestion to read the data from qt App in Arduino

//Finally
With the knowldge of @mrjj

I have solved this issue ,
𝐭𝐡𝐚𝐭 𝐢𝐭𝐬 𝐧𝐨𝐭 𝐡𝐨𝐰 𝐢𝐭 𝐰𝐨𝐫𝐤𝐬. 𝐈𝐓 𝐜𝐚𝐧 𝐣𝐮𝐬𝐭 𝐬𝐡𝐨𝐰 𝐰𝐡𝐚𝐭 𝐜𝐨𝐦𝐞𝐬 𝐟𝐫𝐨𝐦 𝐭𝐡𝐞 𝐀𝐑𝐃 𝐛𝐨𝐚𝐫𝐝. 𝐥𝐢𝐤𝐞 𝐚 𝐝𝐞𝐛𝐮𝐠𝐠𝐢𝐧𝐠 𝐜𝐨𝐧𝐬𝐨𝐥𝐞.

𝐬𝐨 𝐢𝐟 𝐲𝐨𝐮 𝐨𝐩𝐞𝐧 𝐜𝐨𝐦𝐩𝐨𝐫𝐭 𝐰𝐢𝐭𝐡 𝐢𝐭 𝐟𝐢𝐫𝐬𝐭. 𝐭𝐡𝐞𝐧 𝐐𝐭 𝐩𝐫𝐨𝐠𝐫𝐚𝐦 𝐰𝐢𝐥𝐥 𝐠𝐞𝐭 𝐩𝐞𝐫𝐦𝐢𝐬𝐢𝐬𝐨𝐧 𝐞𝐫𝐫𝐨𝐫

𝐬𝐨 𝐢𝐭 𝐰𝐨𝐧𝐭 𝐬𝐡𝐨𝐰 𝐭𝐡𝐞𝐫𝐞 𝐰𝐡𝐚𝐭 𝐐𝐭 𝐬𝐞𝐧𝐝𝐬. 𝐨𝐧𝐥𝐲 𝐰𝐡𝐚𝐭 𝐛𝐨𝐚𝐫𝐝 𝐬𝐞𝐧𝐝𝐬

𝐡𝐭𝐭𝐩𝐬://𝐰𝐰𝐰.𝐢𝐧𝐬𝐭𝐫𝐮𝐜𝐭𝐚𝐛𝐥𝐞𝐬.𝐜𝐨𝐦/𝐢𝐝/𝐇𝐎𝐖-𝐓𝐎-𝐮𝐬𝐞-𝐭𝐡𝐞-𝐀𝐑𝐃𝐔𝐈𝐍𝐎-𝐒𝐄𝐑𝐈𝐀𝐋-𝐌𝐎𝐍𝐈𝐓𝐎𝐑/

𝐬𝐨 𝐮 𝐜𝐚𝐧𝐭 𝐮𝐬𝐞 𝐬𝐞𝐫𝐢𝐚𝐥 𝐦𝐨𝐧𝐢𝐭𝐨𝐫 𝐚𝐭 𝐬𝐚𝐦𝐞 𝐭𝐢𝐦𝐞 𝐚𝐬 𝐭𝐡𝐞 𝐐𝐭 𝐩𝐫𝐨𝐠𝐫𝐚𝐦

mrjj

Hi
You should add check to the

serial->open(QIODevice::ReadWrite);

to see if it fails.

It might not open at all and hence nothing will be seen on the board.

sankarapandiyan

@mrjj Yes i checked in Qt App , by qDebug() its print in qt app and the data is getting in the function
Edited code

void MainWindow ::on_send_clicked()
{
      serial->open(QIODevice::ReadWrite);
      qDebug () << baToSend ; // Here i have checked in Qt
        line = ui->sender->toPlainText();
        QString txt1 = ui->receive->toPlainText();
        /*QString*/ txt3 = ui->aknowmnt->toPlainText();
         if(m_lines.isEmpty()){
            QFile inputFile(QString("/home/adx-soft1/Shankar/serial/myfile1.txt"));
            inputFile.open(QIODevice::ReadOnly);
            if (!inputFile.isOpen())
                return;

            QTextStream stream(&inputFile);
            while(!stream.atEnd()){
                QString line = stream.readLine();
                m_lines.append(line + QString("\r\n"));
            }
        }

        checkAndSendData();
}

But In Arduino I did not get the data received .. @mrjj

JonB

@sankarapandiyan
You still have not shown code which checks the result from serial->open(QIODevice::ReadWrite);. Could you please start by doing that at least. This further applies to other code of yours, e.g. serial->write(baToSend);. If you expect a solution to your issues you should start by introducing the necessary error checking code wherever possible.

Yunus

@sankarapandiyan hi, I also used arduino and Qt by serial communication. I just followed this video series steps This one was very helpful to me

sankarapandiyan

@Yunus Hii i am not making the RGB LED Blinking , Here i am transfering the data from the text file from Qt to Arduino

Yunus

@sankarapandiyan He is also sending texts and numbers to Arduino :). He is controlling arduino by sending letters, and numbers. Thats why I thought maybe helpfull for you. You can also send data to arduino only by using C++. But using Qt makes it easy.

sankarapandiyan

@mrjj @JonB

alternate text

Yes both of you are right .. above image shows my output ,
if i clicked the send button first time ,
"" is printed like this
while clicked second time
line 5 is printed
while third time same is printed

i Dont know why its came like this

sankarapandiyan

@JonB

@JonB said in How to send the Data from Qt App to Arduino by serial communication:

You still have not shown code which checks the result from serial->open(QIODevice::ReadWrite);.

YEs i have shown in above reply

sankarapandiyan

@Yunus Sure thanks a lot i will refer

JonB

@sankarapandiyan
You cannot expect people to help if you show output which simply does not correspond to anywhere in the code you have shown, can you? For example, you have a screenshot showing output where the code you have shown simply does not include any such output lines....

sankarapandiyan

@JonB ok fine.. thanks

ODБOï

@JonB said in How to send the Data from Qt App to Arduino by serial communication:

you have a screenshot showing output where the code you have shown simply does not include any such output lines..

hi, the 2nd line in his on_send_clicked method doas qDebbug() << "serial opened-"

@sankarapandiyan you should put it in a if statement to call qDebug only if open() returns true

if(serial->open(QIODevice::ReadWrite))

JonB

@LeLev said in How to send the Data from Qt App to Arduino by serial communication:

hi, the 2nd line ot his on_send_clicked method doas qDebbug() << "serial opened-"

You are right. I searched the whole page for serial opened (or even seral opened), I have only just seen it is in a screenshot. However, I still do not see where the baToSend used there is declared or set, I only see it elsewhere (local variable inside on_send_clicked()). Nor do I know what it is the text file read in. So it's still pretty hard to know what is going on....

sankarapandiyan

@JonB In text file i have 5 lines ,

line 1
line 2
line 3
line 4
line 5

i want to print these five line in arduino serial monitor , While i clicking send button

sankarapandiyan

@JonB Tried to Edit my code in correct form

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <QList>
#include <QComboBox>
#include <QString>
#include <QTextEdit>
#include <QTime>
#include <QDebug>
#include <QtSerialPort/QSerialPortInfo>
#include <QtSerialPort>
#include <QFile>
#include <QList>
#include <QSerialPort>

MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
    , ui(new Ui::MainWindow)
{

      ui->setupUi(this);
      QString filename1="/home/adx-soft1/Shankar/serial/myfile1.txt";
      QFile file(filename1);
      if(!file.exists()){
          qDebug() << "NO FILE "<<filename1;
      }else{
          qDebug() << filename1<<" ...";
      }
      QString line1;
      ui->sender->clear();
      if (file.open(QIODevice::ReadOnly | QIODevice::Text)){ ui->sender->setText(file.readAll()); }

      QList<QSerialPortInfo> list;
      list = QSerialPortInfo::availablePorts();

      for (int i= 0; i < list.length(); i++)
      {
        ui->comboBox->addItem(list[i].portName());

      }
}

MainWindow::~MainWindow()
{
    serial->close();
    delete ui;
}

void MainWindow::on_pushButton_clicked()
{
    serial = new QSerialPort(this);
    serial->setPortName(ui->comboBox->currentText());
    serial->setBaudRate(QSerialPort::Baud9600);
    serial->setDataBits(QSerialPort::Data8);
    serial->setParity(QSerialPort::NoParity);
    serial->setStopBits(QSerialPort::OneStop);
    serial->setFlowControl(QSerialPort::NoFlowControl);
    serial->open(QIODevice::ReadWrite);
    connect(serial, &QSerialPort::readyRead, this, &MainWindow::serialReceived);

   ui->progressBar->setValue(100);
//    ui->receive->clear();
}
void MainWindow::checkAndSendData()
{
    if(!m_lines.isEmpty()){
        baToSend = m_lines.takeFirst().toUtf8();
        serial->write(baToSend);
        //qDebug() << baToSend << "serial Writed---" ;

        ui->aknowmnt->setText("Sent Message -->" +  QString(baToSend) + "\n");
    }
    else
    {
        ui->aknowmnt->setText("Receiving ");
    }
}


void MainWindow ::on_send_clicked()
{
      //serial->open(QIODevice::ReadWrite);
      qDebug () << baToSend << "seral opened ----" ;

      qDebug() << "Serial: " << serial->isOpen();
      qDebug() << "Error: " << serial->error() << " | " << serial->errorString();

      line = ui->sender->toPlainText();
        QString txt1 = ui->receive->toPlainText();
        /*QString*/ txt3 = ui->aknowmnt->toPlainText();

        qDebug() << "m_lines: " << m_lines;

         if(m_lines.isEmpty()){
            QFile inputFile(QString("/home/adx-soft1/Shankar/serial/myfile1.txt"));
            inputFile.open(QIODevice::ReadOnly);

            if (!inputFile.isOpen()) {
                return;
            }

            QTextStream stream(&inputFile);

            while(!stream.atEnd()) {
                QString strline = stream.readLine();
                m_lines.append(strline + QString("\r\n"));

                qDebug() << "m_lines: " << m_lines;
            }
        }
        checkAndSendData();
}


void MainWindow::serialReceived()
{

    qDebug() << "serial->readAll().trimmed(): " << serial->readAll().trimmed();

    QString glen = serial->readAll().trimmed();

    qDebug() << "glen: " << glen;

     if (glen.length() > 0) {
         ui->receive->append(glen);
        /*QString*/ //line = ui->receive->toPlainText();
        //ui->receive->setText(ui->receive->toPlainText() + line + "\n");
        //ui->receive->setText(line + "\r\n" + glen + "\r\n");
        //line = txt3;
    }
    checkAndSendData();
}

But i did not get the data received in arduino side

sankarapandiyan

@LeLev ok fine i will correct it

sankarapandiyan

@JonB @LeLev @mrjj cant open port : QSerialPort::SerialPortError(PermissionError)
I get the error like this ..

Thanks

jsulm

@sankarapandiyan said in How to send the Data from Qt App to Arduino by serial communication:

PermissionError

Make sure your user has needed access rights for the serial port device file.
See for example https://askubuntu.com/questions/58119/changing-permissions-on-serial-port

sankarapandiyan

@jsulm Is it possible to open the port in both Qt app and Arduino in a same OS ..
Here if i open the port in Qt means , in Arduino ,i got a error the port is changed or not found

while if i open the port in Arduino first means , I got a error message in Qt as (PERMISSION ERROR)

I am Stucked here for a day, I am very new to this arduino topic , So give me some idea abouth this .

Thanks in advance .