IMX8 Reading canbus interface problem

[hixboz]

Hello,

I would like to use can interface in IMX8 board.I hooked up the can0 and can1 interfaces each other. The canbus interface is working when I make loopback test. I wrote two different console apps which are for reading and writing. My reading application is not working . When I write the data from one of canbus interfaces , I couldn't read the data from another canbus interface.The loopback test commands:

ip link set can0 up type can bitrate 500000 sample-point 0.75 dbitrate 4000000 dsample-point 0.8 fd on
ifconfig can0 up
ip link set can1 up type can bitrate 500000 sample-point 0.75 dbitrate 4000000 dsample-point 0.8 fd on
ifconfig can1 up

candump can1
cansend can0 5A1#11.22.33.44.55.66.77.88
killall candump

candump can0
cansend can1 5A1#11.22.33.44.55.66.77.88

My read application is below:

#include <QCoreApplication>
#include <QDebug>
#include <QCanBusDevice>
#include <QCanBusDeviceInfo>
#include <QCanBus>
#include <QString>
#include <QThread>

int main(int argc, char *argv[])
{
QCoreApplication a(argc, argv);
QString canbus_interface;

QList<QCanBusDevice::Filter> list;
QCanBusDevice::Filter f;


if(argc != 2)
{
    qDebug() << "The usage : ./Program_name can0/or/can1/interface";
    qDebug() << "Example : ./read_canbus can0";

}

if(argc == 2)
{
  canbus_interface = argv[1];
}

if (QCanBus::instance()->plugins().contains(QStringLiteral("socketcan"))) {
    qDebug() << "Plugin is avaliable";
}

QString errorString;
QCanBusDevice *device = QCanBus::instance()->createDevice(
    QStringLiteral("socketcan"), canbus_interface, &errorString);

if (!device) {
    qDebug() << errorString;
}
else {
    device->connectDevice();
    qDebug() << "Device connected";
}


while(true){
    while (device->framesAvailable()) {
        const QCanBusFrame frame = device->readFrame();
        QString view;
        if (frame.frameType() == QCanBusFrame::ErrorFrame){
            view = device->interpretErrorFrame(frame);
            qDebug() << "Frame error ";
        }
        else{
            view = frame.toString();
            qDebug() << "Frame available " << view;
        }

    }
    QThread::msleep(10);
}

How can I handle that ? Thanks in advanced.

[kuzulis]

Did you read a documentation at all? Did you see a set of waitForXX methods?

UPD: Please, read the documentation about how the Qt and its event-loop works at all.

[hixboz]

I couldnt get any frame . What are the possible causes of getting not any frame? I dont think is not related with waitForXX methods?

[kuzulis]

No comments...

[Pablo J. Rogina]

@hixboz have you already tried the CAN Bus example?

[KroMignon]

@hixboz said in IMX8 Reading canbus interface problem:

I couldnt get any frame . What are the possible causes of getting not any frame? I dont think is not related with waitForXX methods?

Your application can not work as it is!
QCanBus, like all QObject based classes, needs a working event loop.
The event loop is need to made work the signals/slots feature of the QObject.

Please start with reading documentation and follow the suggestions given @Pablo-J-Rogina, first try out the CAN Bus example application: https://doc.qt.io/qt-5/qtserialbus-can-example.html

Here is an example of a minimal console application: http://treyweaver.blogspot.com/2013/02/qt-console-application-template-tutorial.html

[aha_1980]

https://code.woboq.org/qt5/qtserialbus/src/tools/canbusutil is a command line CAN example