Real time Plotting Line chart

Andrex_Qt

Hello,
i am trying to make a line chart which updates after 1 sec or less, I feed data from SPI to my Line chart 4 points at a time.
I am following the QLinechart example in creator and to update the graph I have used timeout() of a Qtimer to call updater() function does oly chartView.update();
but I always get segmentation Plot.
I am doing this right?is there a better method?

code snippet as follows:

MainWindow
{
 ui->setupUi(this);

//-----SPI initialization-----------

 t1 = new  QTimer(this);
 connect(t1,SIGNAL (timeout()),this,SLOT(spi()));
 t1->start(0);

 t2 = new  QTimer(this);
 connect(t2,SIGNAL (timeout()),this,SLOT(updater()));
 t2->start(1000);

//-----chan[4] data from SPI----

  QLineSeries *series = new QLineSeries();
*series  <<QPointF(0,chan[0])  << QPointF(1,chan[1]) << QPointF(2,chan[2]) <<QPointF(3,chan[3]);

 QChart *chart = new QChart();
 chart->legend()->hide();
 chart->addSeries(series);
 chart->createDefaultAxes();
 //chart->setAxisX(0,series);
 chart->setTitle("Simple line chart example");

 QChartView *chartView = new QChartView(chart);
 chartView->setRenderHint(QPainter::Antialiasing);
 chartView->setParent(ui->verticalFrame);

}

void MainWindow::spi()
{
 //----Get SPI data----------
}


void MainWindow::updater()
{
 //chartView->repaint();
chartView->update();

}

wincak

If you don't mind using a library you can try QCustomPlot.

The Axis tags example shows how to create a periodically updating (40 ms) chart.

Andrex_Qt

@wincak
thanks for the suggestion, I tried it and it works good.
I have two questions:
It doesn't seem to have Pie-Chart, can you confirm?
and is this library free?

Pl45m4

@Andrex_Qt said in Real time Plotting Line chart:

It doesn't seem to have Pie-Chart, can you confirm?

Yes, true. There is no pie-chart as such.

@Andrex_Qt said in Real time Plotting Line chart:

is this library free

QCustomPlot was released under GPL license and is free to use in free software.

asterixxx

https://www.youtube.com/watch?v=lXXUxy5Opds&t=2s

lira

@Pl45m4 is QCustomPlot only for Linux?

mrjj

@lira
Hi and welcome to the forums.
No, it will run most places that Qt can.
It's just a .h and .cpp file you include in your project so it will work on most platforms.

lira

@mrjj thank you :)