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Thread: Sending a "struct" through a serial (with QIODevice::write())

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    Default Sending a "struct" through a serial (with QIODevice::write())

    Hello!

    I have to create a software that communicates with a serial port sending, instead of any chars, a structure. A software that sends bytes I already have, so no problem. The problem is that the function that sends data to the serial port uses the qint64 QIODevice::write ( const QByteArray & byteArray ) in a similar way to this:

    Qt Code:
    1. { //.h
    2. #include <Serial/abstractserial.h>
    3. AbstractSerial *port1;
    4. }
    5.  
    6. {
    7. port1 = new AbstractSerial();
    8. }
    9.  
    10. bool command::Write(QByteArray com)
    11. {
    12. if(!port1->isOpen())
    13. {
    14. emit sendSBMessage("Port closed");
    15. return false;
    16. }
    17. else
    18. {
    19. port1->write(com + "\r\0");
    20. return true;
    21. }
    22. }
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    Now what I have to do is to create a function that instead of sending that QByteArray, it rather sends a structure. But the problem is that the function used by AbstractSerial port1 is the QIODevice::write, and this function is not ready for sending structures as it seems.


    So how do I do this? I have no idea.


    Thanks,


    Momergil

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    Default Re: Sending a "struct" through a serial (with QIODevice::write())

    You must create a function that performs serialization structure to QByteArray. And the recipient must perform the inverse operation.

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    Default Re: Sending a "struct" through a serial (with QIODevice::write())

    Quote Originally Posted by Lesiok View Post
    You must create a function that performs serialization structure to QByteArray. And the recipient must perform the inverse operation.
    Hmmm, not sure that I understood. You mean that I must create some sort of protocol that catch the data from the structure, put it into a QByteArray variable and sends it normally through the serial port, and than the other side, knowing that protocol, will "translate" it?


    Momergil

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    Default Re: Sending a "struct" through a serial (with QIODevice::write())

    You want to read about the QDataStream class and check out this example.
    Declare the << and >> operator overloads as friend to get access to private data in your class.
    !sirius

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    Default Re: Sending a "struct" through a serial (with QIODevice::write())

    Lesiok has the general process, and sirius has a good approach for Qt-to-Qt program communications (although it can do other things). Your requirement is too vague to allow much more specific answers.

    What is at the other end of the transmission? Another Qt program or something else? Do you understand/have intrinsic variable/byte order/character encoding differences? Is the "structure" a simple C++ struct using only simple types, a list, a tree or other graph...? If it is a graph, does it have cycles?

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    Default Re: Sending a "struct" through a serial (with QIODevice::write())

    Quote Originally Posted by Momergil View Post
    Hmmm, not sure that I understood. You mean that I must create some sort of protocol that catch the data from the structure, put it into a QByteArray variable and sends it normally through the serial port, and than the other side, knowing that protocol, will "translate" it?
    Momergil
    Yes. In addition, data transfer without packing in a protocol is sensitive to transmission errors.

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