Segmentation fault while using real time connection with device.

powp

Hi,
I want to write a application which download data form device in real time.
I writed library in c++ using cyusb_control_transfer() for comunicate with my device.
When i use this library in console program all is working.
But when i want to add it in window qt program it has problem with memory.

I made window in .ui file with graphicsView and button.
To button i add function:

void Window::on_ButtonStart_clicked()
{
    drawDataOnScreen();
}

Draw data function:

void Window::drawDataOnScreen()
{
    m_chart = new QChart;
    m_chart->setMinimumSize(721, 301);
    m_chart->setMaximumSize(721, 301);
    m_chart->legend()->hide();

    QLineSeries *series = new QLineSeries;

    cyusb_handle *h;
    h = cyusb_gethandle(0);
    globalResetAllDeviceRegister(h);
    switchONDevice(h);

    unsigned short len = packetLengthRegister(h);
    unsigned int *source = sourceFromPacket(h, len);

    for(int i=0; i<1; i++)
    {
        series->append(0.001*i, source[i+54]);
    }

    delete[] source;

    switchOFFDevice(h);
    globalResetAllDeviceRegister(h);
    closeDevices();

    m_chart->addSeries(series);
    m_chart->createDefaultAxes();
    m_chart->setAcceptHoverEvents(true);

    scene->addItem(m_chart);
}

When i debug i get this:

Signal from system: SIGSEGV
Meaning of signal: Segmentation fault

And it stop in first data transfer:

unsigned char *databuff = new unsigned char[2];

if(cyusb_control_transfer(h, 0x02, 0x04, 0, 0, databuff, 0, TIME_OUT))
        return 1;

What i do worng?

Gojir4

@powp Hi,

Probably cyusb_gethandle(0) returns null or not a valid pointer.

SGaist

Hi and welcome to devnet,

Where are you calling cyusb_control_transfer from ?

Did you declare a cyusb_handle named h class member variable ?

If so you are likely not initialising it and the one you have in drawDataOnScreen is not the same.

powp

I don't know whats hapenned.
I debug my program very cerrfully with much more traps and it starts works.
I didn't change anything in my program.
But thanks for help.

Pablo J. Rogina

@powp if your issue is solved, please don't forget to mark your post as such. Thanks