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Qt CanBus,SYSTEC CAN can't read CAN frames

  • Hello, I'm working on a CAN API.
    I write a frame to my CAN bus device and should receive data in response. I see the received packet in CAN example API when i write that frame.
    The problem is i can't read that received frame when i use QCanBusDevice::readFrame()
    This is my code to read the response:

     QCanBusDevice *device=QCanBus::instance()->createDevice("systeccan","can1.0");
       char data[8]={0x40,0x00,0x10,0x00,0x00,0x00,0x00,0x00};
       QByteArray frame(data,8);
       QCanBusFrame myframe;
       QCanBusFrame frameR=device->readFrame();

  • Lifetime Qt Champion

    Did you try call
    to see if there is something to read ?

    Also, i think it will work better if you connect a slot
    to void QCanBusDevice::framesReceived()
    and there call framesAvailable and readFrame.
    The way you are using it now, suggests its blocking but i think its actually async.

  • @mrjj i created a function processReceivedFrames and connected it to framesReceived() function.
    I still get 0 as number of available frames.
    This is the way i made the connection:

        connect(m_device, &QCanBusDevice::framesReceived, this, &DevicesManagement::processReceivedFrames,Qt::UniqueConnection);

    I'm sure that data should be received i tested that in CAN example like shown in picture below:![alt text]0_1555063572416_qtforum.PNG


  • Lifetime Qt Champion

    Something else must be missing then. If the sample can.

  • @mrjj Thanks you, i'll check my code then.May have made a mistake somewhere.

  • Lifetime Qt Champion

    Yep. good plan.
    Its hard to guess at on forum but the sample is small, so should be easy to spot if its has more code
    for the Can class than you have.

  • Lifetime Qt Champion

    Hi @Babs,

    Just one note:


    That is not needed, as CanFd is disabled by default (and SYSTEC hardware is not FD capable, at least as far as I know).


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