I have some code for Qt below that connects two devices via UART if possible. If not possible, it will display an error string.

void Hardware::initialisePort(QString portName)     //Initialized at balance and controlboard
{
    /*! \brief Method to initialise the com port
     *
     */

    // setup the port in the appropriate way for the platform that the code is compiled for
    this->serialPort = new QextSerialPort(portName, QextSerialPort::EventDriven);   //serialPort now points to this new QextSerialPort, and the string will come from this port.

    // setup port settings
    serialPort->setBaudRate(BAUD9600);
    serialPort->setFlowControl(FLOW_OFF);
    serialPort->setParity(PAR_NONE);
    serialPort->setDataBits(DATA_8);
    serialPort->setStopBits(STOP_1);

    // attempt to open the port for both reading and writing
    if (serialPort->open(QIODevice::ReadWrite) == true)
    {
        // connect the port ready to read signal to the handling slot
        connect(serialPort, SIGNAL(readyRead()), this, SLOT(serialDataReady()));    //readyRead is just signal, not function, serialDataReady is function that breaks up Arduino string

        qDebug() << "Listening for data on" << serialPort->portName();

    }
    else // could not open port communications
    {

        qDebug() << "Device failed to open:" << serialPort->errorString() << ":" << portName;

        // print the issue to the log with the port error string
        //logging() << "Could not open serial port connection: " << serialPort->errorString();
    }
}

I have two ports initialized, as below:

Balance::Balance() :
    Hardware()
{
    // initialise members
    // null values for the unallocated masses
    lastStableMass = -1;
    lastUnstableMass = -1;
    stable = false;
    timeoutStatus = 0;
    hasTimedOut = false;
    calibrationInProgress = false;
    tareOffset = 0;

    this->initialisePort("/dev/tty01"); //Port name is /dev/tty01

    timer.setInterval(2000);
    connect(&timer, SIGNAL(timeout()), this, SLOT(resend()));
    timer.start();
}

ControlBoard::ControlBoard(QObject *obj) :
    Hardware(obj)
{
    /*! \brief Constructor
     *
     */

    this->initialisePort("/dev/ttyO4"); //Port name is /dev/tty04, and that is somewhere on the control board, don't worry about it
    //Initialise port is in hardware.cpp

    this->airTempMessage = "";
    this->valveChangeMessage = "";
    acknowledgementTimer = 0;
    calibrationTimer = 0;
    sendCalibration = -1;

    this->sampleTempTimer = new QTimer;
    connect(sampleTempTimer, SIGNAL(timeout()), this, SLOT(requestSampleTempUpdate()));

    hasTimedOut = false;

    valveOpen = false;

    airTemperature = 0;

    temporaryCalFactor = -1;

    compressorTimer = 0;

    requestValveUpdate();
}

This is something I have received with the code:

Device failed to open: "No Error has occurred" : "/dev/tty01" 
Listening for data on "/dev/ttyO4" 

I am unsure why. I have attempted to do the following:

    else // could not open port communications
    {
        connect(serialPort, SIGNAL(readyRead()), this, SLOT(serialDataReady()));
        //Even though the port is listed as cannot be opened, I attempted to see whether the error signal was a false flag by initializing it anyways.
        qDebug() << "Device failed to open:" << serialPort->errorString() << ":" << portName;

        // print the issue to the log with the port error string
        //logging() << "Could not open serial port connection: " << serialPort->errorString();
    }

This did not result in the port actually opening. Please let me know if more information is required to solve this issue; I will update this question accordingly.

CodePudding user response：

There was a typo. The port was written as "tty01", when it should have been "ttyO1", O for Orange instead of a zero. Thanks to chehrlic for catching it, 0s and Os are a bit too similar in Linux.