How do i integrate my embedded C source codes (for my embedded linux board) with Qt GUI together?



  • Suppose I've my existing C source codes to run on my embedded Linux board and i'd like to create a Qt GUI using e.g. QtWidget application. How do I exactly integrate the Qt GUI and C source codes together? e.g. if I create a GUI to playback video, how to link e.g. a [Open] button to trigger e.g. a video decoder block that will run on my embedded Linux?


  • Moderators

    @embdev Read http://doc.qt.io/qt-5.7/signalsandslots.html
    C can be easily called from C++. You can simply add your C code to your Qt project. Or you can build your C code as a library and link it to your Qt application.



  • @jsulm I see, so more specifically on the implementation level, suppose I create a QtWidget application project, and I've the embedded hardware source codes, should it be a stand alone source page or I should merge inside, say in the mainwindow.cpp?


  • Moderators

    @embdev You should not merge it. What would be the benefit? Keep it separated from your UI code.



  • @jsulm okies, so implementation level is that i'll have a UI source, then it'll call on to the functions in my embedded C code to execute certain features on my embedded Linux board.

    In that sense, my kit, especially my qmake.exe needs to be correctly setup so that when I build, the qmake.exe will build my C codes as well as the GUI codes using my compiler right?


  • Moderators

    @embdev No need to change anything in your kit. Just use .c suffix instead of .cpp for your C code the build system is smart enough to find out which compiler (gcc for C and g++ for C++) to call.
    You just need to add that C files to your .pro file as you do for C++ files.



  • @jsulm got it. so suppose I've added my embedded Linux .c file and then I created a UI button, By using signals & slots feature in Qt, I can link the button to triggering a particular f(x) in my .c file to run some processes on my embedded Linux board. is this train of thought correct?


  • Moderators

    @embdev Yes, it is. Include the C header file where your C function is declared.



  • @jsulm greatly appreciate for the directions! I'll try it out!



  • @jsulm suppose I've created a QtWidget project with main.cpp and mainwindow.cpp sources created. I've also created a simple UI with pushButton to run a particular f(x) in another source code (that access my embedded Linux target directly)

    #include "mainwindow.h"
    #include "ui_mainwindow.h"

    MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
    {
    ui->setupUi(this);
    }

    MainWindow::~MainWindow()
    {
    delete ui;
    }

    void MainWindow::on_pushButton_clicked()
    {

    SAMPLE_VDEC_VdhH264();
    

    }

    The SAMPLE_VDEC_VdhH264(); is actually defined in my embedded source code as one of the options. Is it okay to add the function just like that? as I met with build error saying that that function is not declared in this scope.


  • Qt Champions 2016

    Hi
    You need to include the header file also

    #include "VDEC_VdhH264.H" or where ever
    SAMPLE_VDEC_VdhH264()
    is declared.



  • @mrjj I see. Well, because I've a main.c source file from vendor as sample program, which I've also added into Qt projects. And i'd like to link pushbutton I've created in mainwindow.mpp source file to link to my vendor sample source file function [i.e. SAMPLE_VDEC_VdhH264(); ], Hence there's no header file for the high-level function, as the high-level function is defined in the sample source file.

    Does it mean I've to create a separate header file to include the high-level functions in the sample source file, so that I can add the header file into mainwindow.mpp, containing the high-level function defined in my sample source file, and that I can then just call the functions accordingly?


  • Qt Champions 2016

    Hi
    I would make a new .h file for it as not to be messy.
    This file would list the functions from main.c

    However, if the main.cpp is included in the project, you can use without .h file like this

    void/int SAMPLE_VDEC_VdhH264(); //// forward declare it

    void MainWindow::on_pushButton_clicked()
    {
    SAMPLE_VDEC_VdhH264(); // call it
    }



  • @mrjj I've included the headers from my sample source file in main.mpp as well, with the SAMPLE_VDEC_VdhH264 function declaration.

    In mainwindow.cpp

    #include "mainwindow.h"
    #include <QApplication>

    #include <stdio.h>
    #include <stdlib.h>
    #include <string.h>
    #include <sys/types.h>
    #include <sys/stat.h>
    #include <sys/ioctl.h>
    #include <sys/poll.h>
    #include <sys/time.h>
    #include <fcntl.h>
    #include <errno.h>
    #include <pthread.h>
    #include <math.h>
    #include <unistd.h>
    #include <signal.h>
    #include "sample_comm.h"

    int main(int argc, char *argv[])
    {
    QApplication a(argc, argv);
    MainWindow w;
    w.show();

    int SAMPLE_VDEC_VdhH264();
    
    return a.exec();
    

    }

    In mainwindow.cpp, invoke the function SAMPLE_VDEC_VdhH264

    #include "mainwindow.h"
    #include "ui_mainwindow.h"

    MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
    {
    ui->setupUi(this);
    }

    MainWindow::~MainWindow()
    {
    delete ui;
    }

    void MainWindow::on_pushButton_clicked()
    {

    SAMPLE_VDEC_VdhH264();

    }


    I tried to build again but it says the same error though (i.e. in mainwindow.cpp, 'SAMPLE_VDEC_VdhH264 was not declared in this scope')


  • Qt Champions 2016

    int main(int argc, char *argv[])
    {
    QApplication a(argc, argv);
    MainWindow w;
    w.show();

    int SAMPLE_VDEC_VdhH264(); <<<< why here??? that is forward in main. not what i ment.

    return a.exec();
    }

    Did you make a .h file with ?
    int SAMPLE_VDEC_VdhH264();

    else
    i mean like

    int SAMPLE_VDEC_VdhH264();

    void MainWindow::on_pushButton_clicked()
    {

    SAMPLE_VDEC_VdhH264();

    }



  • @mrjj my apologies, I've read it otherwise. However, it seems that the compiler can't find my function definition. It's a separate source code which I've added into the project entitled "sample_vdec.c". The function definition in this source code is:

    HI_S32 SAMPLE_VDEC_VdhH264(HI_VOID)
    {
    ....................
    }

    I've amended to the following:

    in mainwindow.cpp:

    #include "mainwindow.h"
    #include "ui_mainwindow.h"
    #include "hi3536mainfx.h"

    MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
    {
    ui->setupUi(this);
    }

    MainWindow::~MainWindow()
    {
    delete ui;
    }

    HI_U32 SAMPLE_VDEC_VdhH264();

    void MainWindow::on_pushButton_clicked()
    {

    SAMPLE_VDEC_VdhH264();

    }

    in main.cpp

    #include "mainwindow.h"
    #include <QApplication>

    int main(int argc, char *argv[])
    {
    QApplication a(argc, argv);
    MainWindow w;
    w.show();

    return a.exec();
    

    }

    in header

    #ifndef HI3536MAINFX_H
    #define HI3536MAINFX_H
    #include <hi_type.h>
    #include <hi_comm_vb.h>

    typedef struct hiVDEC_USERPIC_S
    {
    HI_U32 u32PicWidth;
    HI_U32 u32PicHeigth;
    VB_POOL u32PoolId;
    VB_BLK u32BlkHandle;
    HI_U32 u32PhyAddr;
    HI_VOID *pVirAddr;
    }VDEC_USERPIC_S;

    HI_U32 SAMPLE_VDEC_VdhH264();

    #endif // HI3536MAINFX_H


  • Qt Champions 2016

    since you have a
    HI3536MAINFX_H
    with
    HI_U32 SAMPLE_VDEC_VdhH264();

    you dont need it over
    void MainWindow::on_pushButton_clicked()
    also.

    so compiles now?



  • @mrjj discovered some error in datatype in my code but rectified it but still unable to compile. The error says undefined reference to SAMPLE_VDEC_VhdH264(); and ld returned 1 exit status.
    When I highlighted VDEC_SAMPLEVhdH264(); in main.cpp and hit [F2] cursor recursively, it brings me to the sample source code where this function is defined but doesn't brings me to the header where I declared this function.

    ** in main.cpp **

    #include "mainwindow.h"
    #include "ui_mainwindow.h"
    #include "hi3536mainfx.h"
    
    MainWindow::MainWindow(QWidget *parent) :
        QMainWindow(parent),
        ui(new Ui::MainWindow)
    {
        ui->setupUi(this);
    }
    
    MainWindow::~MainWindow()
    {
        delete ui;
    }
    
    
    void MainWindow::on_pushButton_clicked()
    {
    
       SAMPLE_VDEC_VdhH264();
    
    }
    

    ** in sample source code where SAMPLE_VDEC_VhdH264() is defined: **

    HI_S32 SAMPLE_VDEC_VdhH264(HI_VOID)
    {
        VB_CONF_S stVbConf, stModVbConf;
        HI_S32 i, s32Ret = HI_SUCCESS;
        VDEC_CHN_ATTR_S stVdecChnAttr[VDEC_MAX_CHN_NUM];
        VdecThreadParam stVdecSend[VDEC_MAX_CHN_NUM];
        VPSS_GRP_ATTR_S stVpssGrpAttr[VDEC_MAX_CHN_NUM];
     ..... ..... .....
    }
    

    ** in my header file **

    #ifndef HI3536MAINFX_H
    #define HI3536MAINFX_H
    #include "hi_comm_vb.h"
    #include "hi_type.h"
    
    typedef struct hiVDEC_USERPIC_S
    {
        HI_U32   u32PicWidth;
        HI_U32   u32PicHeigth;
        VB_POOL  u32PoolId;
        VB_BLK   u32BlkHandle;
        HI_U32   u32PhyAddr;
        HI_VOID  *pVirAddr;
    }VDEC_USERPIC_S;
    
    HI_S32 SAMPLE_VDEC_VdhH264(HI_VOID);
    
    #endif // HI3536MAINFX_H
    

  • Moderators

    @embdev said in How do i integrate my embedded C source codes (for my embedded linux board) with Qt GUI together?:

    in sample source code where SAMPLE_VDEC_VhdH264() is defined:

    Is the source file containing SAMPLE_VDEC_VhdH264() part of your project and is it built?



  • @jsulm yes it is, the source file containing the function definition SAMPLE_VDEC_VhdH264() is added physically into the project file.


  • Moderators

    @embdev You should check the complete "Compile Output" to see whether that file was really built and linked to your executable.
    Don't forget that you should always execute qmake again (and do a rebuild) if you change the .pro file!



  • @jsulm I did a clean, followed by build again in Qt Creator IDE environment but still receiving the error:
    In the .pro file, my source file containing the SAMPLE_VDEC_VhdH264() is also included under SOURCES +=

    This is an output from the compile tab:

    5:39:36: Running steps for project vdec_test...
    15:39:36: Configuration unchanged, skipping qmake step.
    15:39:36: Starting: "/usr/bin/make" 
    arm-hisiv400-linux-g++ -c -pipe -O2 -Wall -W -D_REENTRANT -DQT_NO_DEBUG -DQT_GUI_LIB -DQT_NETWORK_LIB -DQT_CORE_LIB -I../../v1_QtEmbedded-4.8.6/mkspecs/qws/linux-hisiv400-arm-g++ -I../vdec_test -I../../v1_QtEmbedded-4.8.6/include/QtCore -I../../v1_QtEmbedded-4.8.6/include/QtNetwork -I../../v1_QtEmbedded-4.8.6/include/QtGui -I../../v1_QtEmbedded-4.8.6/include -I../../mpp_single/sample/common -I../../mpp_single/include -I../../mpp_single/extdrv/tlv320aic31 -I../../v1_QtEmbedded-4.8.6/examples/multimedia/videographicsitem -I../../mpp_single/lib -I../../mpp_single/include -I../../mpp_single/include -I../../mpp_single/include -I../../mpp_single/include -I../../mpp_single/include -I../../mpp_single/include -I. -I. -I../vdec_test -I. -o mainwindow.o ../vdec_test/mainwindow.cpp
    arm-hisiv400-linux-g++ -Wl,-O1 -Wl,-rpath,/home/aa/Hi3536_SDK_V2.0.4.0/v1_QtEmbedded-4.8.6/lib -o vdec_test main.o mainwindow.o sample_comm_audio.o sample_comm_ivs.o sample_comm_sys.o sample_comm_vda.o sample_comm_vdec.o sample_comm_venc.o sample_comm_vi.o sample_comm_vo.o sample_comm_vpss.o sample_vdec.o moc_mainwindow.o    -L/home/aa/Hi3536_SDK_V2.0.4.0/v1_QtEmbedded-4.8.6/lib -L/home/aa/Hi3536_SDK_V2.0.4.0/Working\ folder/vdec_test/../../mpp_single/lib/ -ldnvqe -lhdmi -lmpi -ljpeg -lupvqe -lVoiceEngine -lQtGui -L/home/aa/Hi3536_SDK_V2.0.4.0/v1_QtEmbedded-4.8.6/lib -lQtNetwork -lQtCore -lm -ldl -lrt -lpthread 
    mainwindow.o: In function `MainWindow::on_pushButton_clicked()':
    mainwindow.cpp:(.text+0xbc): undefined reference to `SAMPLE_VDEC_VdhH264()'
    mainwindow.o: In function `MainWindow::on_pushButton_2_clicked()':
    mainwindow.cpp:(.text+0xc0): undefined reference to `SAMPLE_VDEC_VdhH265()'
    collect2: error: ld returned 1 exit status
    Makefile:125: recipe for target 'vdec_test' failed
    make: *** [vdec_test] Error 1
    15:39:37: The process "/usr/bin/make" exited with code 2.
    Error while building/deploying project vdec_test (kit: HI3536 Qt4.8)
    When executing step "Make"
    15:39:37: Elapsed time: 00:01.
    

  • Moderators

    @embdev To me it doesn't look like a complete rebuild as in the second compiler call object files, which were not compiled before, are already linked:

    arm-hisiv400-linux-g++ -Wl,-O1 -Wl,-rpath,/home/aa/Hi3536_SDK_V2.0.4.0/v1_QtEmbedded-4.8.6/lib -o vdec_test main.o mainwindow.o sample_comm_audio.o sample_comm_ivs.o sample_comm_sys.o sample_comm_vda.o sample_comm_vdec.o sample_comm_venc.o sample_comm_vi.o sample_comm_vo.o sample_comm_vpss.o sample_vdec.o moc_mainwindow.o    -L/home/aa/Hi3536_SDK_V2.0.4.0/v1_QtEmbedded-4.8.6/lib -L/home/aa/Hi3536_SDK_V2.0.4.0/Working\ folder/vdec_test/../../mpp_single/lib/ -ldnvqe -lhdmi -lmpi -ljpeg -lupvqe -lVoiceEngine -lQtGui -L/home/aa/Hi3536_SDK_V2.0.4.0/v1_QtEmbedded-4.8.6/lib -lQtNetwork -lQtCore -lm -ldl -lrt -lpthread
    

    Please do a rebuild.
    In which file is SAMPLE_VDEC_VhdH264() defined?



  • @jsulm I've deleted the object files away in my build-release folder. I think could be due to datatype declaration of my function, when it's invoked as HI_32 SAMPLE_VDEC_VdhH264(); in the main.cpp, then the project can be compiled, i.e.:

    ** in main.cpp **

    #include "mainwindow.h"
    #include "ui_mainwindow.h"
    #include "hi3536mainfx.h"
    
    MainWindow::MainWindow(QWidget *parent) :
        QMainWindow(parent),
        ui(new Ui::MainWindow)
    {
        ui->setupUi(this);
    }
    
    MainWindow::~MainWindow()
    {
        delete ui;
    }
    
    
    void MainWindow::on_pushButton_clicked()
    {
    
      HI_S32 SAMPLE_VDEC_VdhH264();
    
    }

  • Moderators

    @embdev Now you are declaring a function with same name, you are not calling it.
    Functions are not called like this in C/C++.
    You should really check your project configuration and sources.



  • @jsulm I see, project configurations meaning the .pro file?


  • Moderators

    @embdev yes


  • Qt Champions 2016

    @jsulm
    Hi
    I wonder if
    extern "c" {
    #include "hi3536mainfx.h"
    }

    is needed?


  • Moderators


  • Qt Champions 2016

    @jsulm
    Well im not sure. Just realized I never tried a .c file with mingw and see if it will cpp compile it or
    it does in fact need extern "c". :)


  • Qt Champions 2016

    @mrjj said in How do i integrate my embedded C source codes (for my embedded linux board) with Qt GUI together?:

    Well im not sure.

    It is absolutely needed. C++ supports overloading (which C obviously doesn't) and that ABI-wise is realized by decorating the symbols. So to be able to link properly, you need to tell the compiler that you're actually expecting C-linkage for the functions.


  • Qt Champions 2016

    @kshegunov
    Thank you. The reason for my doubts is that my old compiler compiles all as cpp and
    hence never needs it. And using Mingw so far, all files been cpp so was not sure if extension .c
    would actually trigger different compile. And it does - so that's a key thing for c-files.



  • @jsulm @mrjj wow, that's really good advice for appending extern "C" { #..... }
    After adding this line, my source is able to compile successfully and boot into my embedded target Linux. Of course it's not fully up because my target source code have other issues but I guess on Qt side, it's resolved!

    Thank you very much folks!


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