Qt QSerialPort Read Write - c++

Question

I have issue with reading and writing from/to QSerialPort. I read what I have written. Here is some example code that proves that. Maybe I need to write and read from different channels. Code's provided below thx in advance. Provided log of the program with image.
Log of the program here
MainWindow.h
#ifndef MAINWINDOW_H
#define MAINWINDOW_H
#include <QMainWindow>
#include <QSerialPort>
#include <QTimer>
#include <QDebug>
class MainWindow : public QMainWindow
{
Q_OBJECT
public:
MainWindow(QWidget *parent = 0);
~MainWindow();
private:
QSerialPort *serialPort;
QTimer* sendTimer;
QByteArray receiveDataBuffer;
private slots:
void onReadyRead();
void onSendDataTimeout();
};
#endif // MAINWINDOW_H
MainWindows.cpp
#include "mainwindow.h"
MainWindow::MainWindow(QWidget *parent)
: QMainWindow(parent),
serialPort(new QSerialPort),
sendTimer(new QTimer)
{
sendTimer->setInterval(1000);
serialPort->setPortName("COM5");
serialPort->setBaudRate(QSerialPort::Baud115200);
serialPort->setParity(QSerialPort::Parity::NoParity);
serialPort->setDataBits(QSerialPort::DataBits::Data8);
serialPort->setStopBits(QSerialPort::StopBits::TwoStop);
serialPort->open(QSerialPort::OpenModeFlag::ReadWrite);
connect(serialPort,&QSerialPort::readyRead,this,&MainWindow::onReadyRead);
connect(sendTimer,&QTimer::timeout,this,&MainWindow::onSendDataTimeout);
sendTimer->start();
}
MainWindow::~MainWindow()
{
}
void MainWindow::onReadyRead()
{
receiveDataBuffer.append(serialPort->readAll());
if (receiveDataBuffer.contains('^') && receiveDataBuffer.contains('$') && receiveDataBuffer.lastIndexOf('$') < receiveDataBuffer.lastIndexOf('^')) {
QByteArray extractedByteArray;
for(int i = receiveDataBuffer.lastIndexOf("$") ; i < receiveDataBuffer.lastIndexOf("^") + 1 ; i++){
extractedByteArray.append(receiveDataBuffer[i]);
}
qDebug()<<"Received:"<<extractedByteArray<<endl;
receiveDataBuffer.clear();
}}
void MainWindow::onSendDataTimeout()
{
qint64 result = serialPort->write("$10,0,123,123^");
bool flush = serialPort->flush();
result != -1 && flush ? qDebug()<<"Data sent"<<endl:qDebug()<<"Failed to send data"<<endl;
}
main.cpp
#include "mainwindow.h"
#include <QApplication>
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
MainWindow w;
w.show();
return a.exec();
}

Answer 1

First of all, try to connect the different signals that are emitted when you read/write that from your port.
For instance to check that the data has been sent properly, according to the documentation you can use the signal QIODevice::bytesWritten:
The signal is emitted every time a payload of data has been written to the device's current write channel. The bytes argument is set to the number of bytes that were written in this payload.
connect(serialPort,&QSerialPort::bytesWritte, this, [](const qint64 bytes) {
qDebug() << "Sent data: " << bytes << " bytes.";
});
To read the data, as you already did, you need to check the QIODevice::readyRead signal:
This signal is emitted once every time new data is available for reading from the device's current read channel. It will only be emitted again once new data is available, such as when a new payload of network data has arrived on your network socket, or when a new block of data has been appended to your device.
Regarding the problem you described, the first step to do is to ensure that your decive has not been configured to work in echo-mode. To turn it off, you will need to check your device interface.
If this is not the problem, check the available ports by using `QSerialPort::availablePorts and ensure that you are connecting to the right one. For example, to connect to the first port, you can do something like this and check that the configuration is compatible with your device:
auto serialInfo = QSerialPortInfo::availablePorts();
serialPort->setPort(serialInfo[0])
auto ret = serialPort.open(QSerialPort::ReadWrite)
&& serialPort.setBaudRate(QSerialPort::Baud38400)
&& serialPort.setDataBits(QSerialPort::Data8)
&& serialPort.setStopBits(QSerialPort::OneStop)
&& serialPort.setParity(QSerialPort::NoParity);
qDebug() << "Port has been configured properly?: " << ret;
If the problem persist, you can get the native handler and modify its properties by calling QSerailPort::handle().
If the platform is supported and the serial port is open, returns the native serial port handle; otherwise returns -1.
The last option, it does not work in all platforms. Worse scenario, take a look into the official docs of termios. It provides a low-level interface that allows you to enable/disable the echo mode.
struct termios options;
tcgetattr(file, &options);
cfmakeraw(&options);
options.c_lflag &= ~(ECHO | ECHOE); // Add or disable the flags
tcsetattr(file, TCSANOW, &options);

Answer 2

The problem was in
serialPort->setStopBits(QSerialPort::StopBits::TwoStop);
The other device was connected to serial port with QSerialPort::StopBits::OneStop.
So changing the stop bits serialPort->setStopBits(QSerialPort::StopBits::OneStop);
solved the problem and there were no echoes anymore.Thx.