UI hangs when either QThread or QTimer invoked

[saman_artorious]

My program continuously reads from serial port. Firstly, I used QTimer and set the interval to 300 mlscnd, this makes UI interaction very slow. I though of converting QTimer to QThread, as QTimer runs in the UI Thread, so, I added QThread class and used msleep() inside the while() loop to control the trigger.
Unfortunately, the program is still slow, I can clearly understand this when I enter digits in the UI. My last guess of where the speed reduction might have come from is emit, as you see below:

void PlcTimer::run(){
    while(1)
    {
        qDebug() << "updateJack()";
 
        const char str[]={UPDATE_m};
    #if DEBUG
        QByteArray  built(str, 3);
        qDebug() << built.toHex();
    #endif
        emit m_sendToRS((char* )str, 3);
        this->msleep(500);
        //sleep(300);
    }
}

void PlcTimer::run(){
    while(1)
    {
        qDebug() << "updateJack()";

        const char str[]={UPDATE_m};
    #if DEBUG
        QByteArray  built(str, 3);
        qDebug() << built.toHex();
    #endif
        emit m_sendToRS((char* )str, 3);
        this->msleep(500);
        //sleep(300);
    }
}

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emit is a UI object, so whatever it is I am suspicious of its interconnection over the UI. do you have any idea how I can resolve the low speed?

[wysota]

First of all emitting a pointer to a local variable to a different thread is not safe. Second of all, show how you use the thread.

[saman_artorious]

in the MainWindow, I use a new instance of the Object, new PlcTimer() and connect the it to the serial SLOT, then I call the start() me

[wysota]

Show relevant code please. What is the signal connected to?

[saman_artorious]

inside MainWindow:

plcTimer = new PlcTimer();
    connect(plcTimer, SIGNAL(jack_sendToRS(char*,int)), rs_plc, SLOT(rs_plcDataAqustn(char*,int)));
    plcTimer->start();
    rs_plc->rs_plcOpenPort((char *)"/dev/ttyS0"); /*/dev/ttyS3*/

plcTimer = new PlcTimer();
    connect(plcTimer, SIGNAL(jack_sendToRS(char*,int)), rs_plc, SLOT(rs_plcDataAqustn(char*,int)));
    plcTimer->start();
    rs_plc->rs_plcOpenPort((char *)"/dev/ttyS0"); /*/dev/ttyS3*/

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QThread signal or QTimer signal connects to serial SLOT which write n reads packet to and from serial port:

bool RS::rs_plcDataAqustn(char* data, int len)
{    
    QByteArray rd15Bytes;
 
    //    QByteArray built((char*)data, 6) ;
    //    qDebug() << built.toHex();
 
 
    if(!rs_serialWrite(data, len))
    {
        qDebug() << "Failure:( rs_dataqustn: rs_plcWrite(data, len)";
        emit plc_port_dscntd();
        return false;
    }
 
    if(len == 3)
    {
        qDebug() << "len = 3";
 
        rs_delay();
 
        if(rs_plcRead(&rd15Bytes))
        {
            qDebug() << rd15Bytes.length();
            //qDebug() << "->" << rd15Bytes.toHex();
 
            if(rd15Bytes.isEmpty())
            {
                emit logMessage("Failure:( rs_dataAqustn, if(rd15Bytes.isEmpty())");
            }
            else
            {
                if(!rs_plcCheckChecksum(&rd15Bytes))
                    emit logMessage("Failure:( rs_dataAqustn, if(!rs_plcCheckChecksum(&rd15Bytes))");
                else
                {
                    emit rs_plcSendRdPacket(rd15Bytes);
 
                    if(!rs_serialWrite((char* )"0x06", 1))
                    {
                        qDebug() << "Failure:( rs_dataqustn: rs_plcWrite(PLC_ACK, 1)";
                    }
                }
            }
        }
        else
        {
            emit plc_hmiBoard_dscntd();
        }
    }
 
    return true;
}

bool RS::rs_plcDataAqustn(char* data, int len)
{    
    QByteArray rd15Bytes;

    //    QByteArray built((char*)data, 6) ;
    //    qDebug() << built.toHex();


    if(!rs_serialWrite(data, len))
    {
        qDebug() << "Failure:( rs_dataqustn: rs_plcWrite(data, len)";
        emit plc_port_dscntd();
        return false;
    }

    if(len == 3)
    {
        qDebug() << "len = 3";

        rs_delay();

        if(rs_plcRead(&rd15Bytes))
        {
            qDebug() << rd15Bytes.length();
            //qDebug() << "->" << rd15Bytes.toHex();

            if(rd15Bytes.isEmpty())
            {
                emit logMessage("Failure:( rs_dataAqustn, if(rd15Bytes.isEmpty())");
            }
            else
            {
                if(!rs_plcCheckChecksum(&rd15Bytes))
                    emit logMessage("Failure:( rs_dataAqustn, if(!rs_plcCheckChecksum(&rd15Bytes))");
                else
                {
                    emit rs_plcSendRdPacket(rd15Bytes);

                    if(!rs_serialWrite((char* )"0x06", 1))
                    {
                        qDebug() << "Failure:( rs_dataqustn: rs_plcWrite(PLC_ACK, 1)";
                    }
                }
            }
        }
        else
        {
            emit plc_hmiBoard_dscntd();
        }
    }

    return true;
}

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Read from Plc:

bool RS::rs_plcRead(QByteArray *data)
{
    unsigned char buff[128];
    int len, tries;
 
    tries = 0;
 
    while(tries < 13)
    {
        len = read(fd, buff, PLC_READ_BYTE);
 
        if((buff[0] == PLC_HEADER) && (len == PLC_READ_BYTE))
        {
            data->append((char *)buff, PLC_READ_BYTE);
            //qDebug() << data->toHex();
            return true;
        }
        else
        {
            tries++;
            qDebug() << "retry";
        }
    }
 
    return false;
}

bool RS::rs_plcRead(QByteArray *data)
{
    unsigned char buff[128];
    int len, tries;

    tries = 0;

    while(tries < 13)
    {
        len = read(fd, buff, PLC_READ_BYTE);

        if((buff[0] == PLC_HEADER) && (len == PLC_READ_BYTE))
        {
            data->append((char *)buff, PLC_READ_BYTE);
            //qDebug() << data->toHex();
            return true;
        }
        else
        {
            tries++;
            qDebug() << "retry";
        }
    }

    return false;
}

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should you need more info, please note it.

[wysota]

You really have to provide more code or better yet a minimal compilable example reproducing the problem, I'm not a seer. Currently I'd have to ask about each and every vaguely named variable in your code.

[saman_artorious]

WYSOTA!
I found out what was lowering down system speed. emit n signals are handled by UI, the main program Thread. Connecting object to serial port class as you see above is not a good idea, as these all are handled by UI Thread. Hence, reducing UI interaction speed. I changed Serial class slot to a static function and called the function directly without using emit. Now, two threads are running every 300 milscnd in the background, without using emit and without conflicting UI user interaction!

[wysota]

Emitting signals doesn't slow down things. If it did in your case then your code had to be incorrect.

[kuzulis]

saman_artorious,

Why to you not to use ready libraries for operation with the serial ports and do not bother QThread and QTimer?
Or you have any weighty reasons to use the himself serial port implementation with such perversions?