To develop my program first without connecting two physical machines on serial port, I downloaded and used this program to simulate COM ports: https://sourceforge.net/projects/com0com/ I connected virtual COM4 to virtual COM5. It works fine.
Using Br@y's Terminal program, I tested if I connect to COM4 in one Terminal instance, and to COM5 in another instance on the same computer, the data that I send on one terminal arrives in the other terminal, and vice versa. Terminal program: https://sites.google.com/site/terminalbpp/
Now let's see the problem: I used SerialPortReader class from this official Qt sample code for async serial read: https://code.qt.io/cgit/qt/qtserialport.git/tree/examples/serialport/creaderasync It connects to COM5 and sets baud rate to 9600 successfully, but no data arrives if I send something via Terminal to COM4, so: SerialPortReader runs through with no error, but after then, no matter what message I send on my Terminal instance, handleReadyRead, handleError, and handleTimeout never get called.
(If I have already a terminal emulator connected to the virtual COM5 port, then connection in my C program fails, so indeed the open() check works fine. Also, if I try to send more than one messages to my program via the virtual COM4 port, Terminal freezes, which is a clear sign of that the previous message has not yet been read on the other side(COM5).)
I have googled a lot, but have not yet found any solutions. Someone here said that it is/was a bug Qt Serial Port Errors - Data not getting read and that the problem is in qserialport_win.cpp, but even if I change that and compile my program again, nothing happens. I use the following code to create the class, but the class' content is unchanged, I use it as I found in the sample program:
// Serial comm init
QSerialPort serialPort;
QString serialPortName = "COM5";
serialPort.setPortName(serialPortName);
int serialPortBaudRate = 9600;
if (serialPort.open(QIODevice::ReadOnly)) {
if(serialPort.setBaudRate(serialPortBaudRate) &&
serialPort.setDataBits(QSerialPort::Data8) &&
serialPort.setParity(QSerialPort::NoParity) &&
serialPort.setStopBits(QSerialPort::OneStop) &&
serialPort.setFlowControl(QSerialPort::NoFlowControl)) {
//SerialPortReader serialPortReader(&serialPort);
SerialPortReader serialPortReader(&serialPort, this);
} else {
std::cout << "Failed to set COM connection properties " << serialPortName.toStdString() << serialPort.errorString().toStdString() << std::endl;
}
} else {
std::cout << "Failed to open port " << serialPortName.toStdString() << serialPort.errorString().toStdString() << std::endl;
}
I would appreciate any help. Thanks!
CodePudding user response:
Today I figured out a sketchy but working version:
SerialPortReader.h
#pragma once
#include <QtCore/QObject>
#include <QByteArray>
#include <QSerialPort>
#include <QTextStream>
#include <QTimer>
class SerialPortReader : public QObject {
Q_OBJECT
public:
explicit SerialPortReader(QObject *parent = 0);
~SerialPortReader() override;
void close();
private:
QSerialPort *serialPort = nullptr;
QByteArray m_readData;
QTimer m_timer;
public slots:
void handleReadyRead();
//void handleTimeout();
//void handleError(QSerialPort::SerialPortError error);
};
SerialPortReader.cpp
#include <iostream>
#include "SerialPortReader.h"
SerialPortReader::SerialPortReader(QObject *parent) : QObject(parent)
{
serialPort = new QSerialPort(this);
const QString serialPortName = "COM4"; //argumentList.at(1);
serialPort->setPortName(serialPortName);
const int serialPortBaudRate = QSerialPort::Baud9600;
serialPort->setBaudRate(serialPortBaudRate);
if (!serialPort->open(QIODevice::ReadOnly)) {
std::cout << "Failed to open port" << std::endl;
//return 1;
}
std::cout << "SerialPortReader(QSerialPort *serialPort, QObject *parent)" << std::endl;
connect(serialPort, SIGNAL(readyRead()), this, SLOT(handleReadyRead()), Qt::QueuedConnection);
// connect(serialPort, &QSerialPort::readyRead, this, &SerialPortReader::handleReadyRead);
//connect(serialPort, &QSerialPort::errorOccurred, this, &SerialPortReader::handleError);
//connect(&m_timer, &QTimer::timeout, this, &SerialPortReader::handleTimeout);
//m_timer.start(5000);
}
void SerialPortReader::handleReadyRead()
{
std::cout << "handleReadyRead()" << std::endl;
m_readData.append(serialPort->readAll());
if (!m_timer.isActive())
m_timer.start(5000);
}
/*
void SerialPortReader::handleTimeout()
{
std::cout << "handleTimeout()" << std::endl;
if (m_readData.isEmpty()) {
std::cout << "No data was currently available for reading" << std::endl;
} else {
std::cout << "Data successfully received" << std::endl;
//m_standardOutput << m_readData << Qt::endl;
}
//QCoreApplication::quit();
}
void SerialPortReader::handleError(QSerialPort::SerialPortError serialPortError)
{
std::cout << "handleError()" << std::endl;
if (serialPortError == QSerialPort::ReadError) {
std::cout << "An I/O error occurred while reading" << std::endl;
//QCoreApplication::exit(1);
}
}
*/
SerialPortReader::~SerialPortReader() {
close();
}
// Close the files, filestreams, etc
void SerialPortReader::close() {
// ...
}
... and in my QApplication code you just need to include the .h and write this to instantiate the serial listener:
SerialPortReader *serialPortReader = new SerialPortReader(this);