Qt graphicsView error signal

[Macive Xiong]

Hi guys,

I am trying to draw something on graphicsView, but there are some error signal shows up, it's like:

qt error signal

I use Arduino to run the process, the code is like:

while(y <= 5){

       for (float x = voltx; x <= 4.96; x += 0.01){
       Serial.print("y = ");
       Serial.println(y*102.4);
       Serial.print("x = ");
       Serial.println(x*102.4);
       analogWrite(XPin, x * 51.49);
       delay(100);

       
       }
       
       y += 0.05;
       Serial.print("y = ");
       Serial.println(y*102.4);
       analogWrite(YPin, y * 51.49);
      

       for (float x = 4.95; x >= voltx - 0.01; x -= 0.01){
       Serial.print("y = ");
       Serial.println(y*102.4);
       Serial.print("x = ");
       Serial.println(x*102.4);
       analogWrite(XPin, x * 51.49);
       delay(100);
  
     }

       y += 0.05;
       Serial.print("y = ");
       Serial.println(y*102.4);
       analogWrite(YPin, y * 51.49);
      

Input the voltage from 0 to 4.96 volt and transfer it to pixels, but the error signal occur in the region I didn't set for scanning. How is it happened?

Qt code:

void MainWindow::updateP(){
    if(!open) return;

    QTextStream stream(arduino);
    QString line;
    while(stream.readLineInto(&line)){
        QRegularExpression re("([x,y,p,a,b]) = ([0-9]{1,4})");
        QRegularExpressionMatchIterator i=re.globalMatch(line);
        while(i.hasNext()){
            QRegularExpressionMatch match=i.next();
            if(!match.hasMatch()){
                qDebug() << "No match!";
                continue;
            }
            QString xoryorporaorb=match.captured(1);
            QString matched=match.captured(2);

            bool ok=false;
            if(xoryorporaorb=="x") x=matched.toFloat(&ok);
            else if(xoryorporaorb=="y") y=matched.toFloat(&ok);
            else if(xoryorporaorb=="p") p=matched.toFloat(&ok);
            else if(xoryorporaorb=="a") a=matched.toFloat(&ok);
            else if(xoryorporaorb=="b") b=matched.toFloat(&ok);
            else continue;
            if(!ok){
                qDebug() << "Could not convert \"" << matched <<"\" to an integer!";
                continue;
            }

            QBrush whiteBrush(Qt::white);
            QPen whitePen(Qt::white, 1.);
            scene->addEllipse(a, b, 5, 5, whitePen, whiteBrush);

Please give me some suggestion kindly, thanks!

p.s Funny thing is, this error didn't happen if I use mega2560, it's about the processing time?

[jsulm]

@Macive-Xiong What is the error? I only see garbage in the link you posted.

[Macive Xiong]

Hi @jsulm
yes, that's what I meant, in the link I posted is the picture I took, the error signal is the points in the circle, I didn't input the position there but somehow it showed up. Any suggestion?

[jsulm]

@Macive-Xiong I still don't understand: what do you mean by "error signal"?

[Macive Xiong]

@jsulm

OK!! From the photo in that link, you can see a bunch of lines in the right of the pic. That's the right position I would like to set the points on. But in the up and left of the pic I circled , you can see some points and lines which are not what I want. I didn't set the points on those positions which is I think it's a error signal. I am not sure if this is a right reference for that but since I don't need those points, but it showed... Any suggestion?

Btw, I am thinking about grayscale, is it possible that I could do some grayscale in my QGraphicsView, instead of setting points?

Thank you so much:)

[jsulm]

@Macive-Xiong Well, if there are points then you most probably put them there. You should check all the coordinates you're getting (a/b) - you can print them via qDebug() << a << b;