Solved Triying to create a custom signal with threads

[aurquiel]

I am working with two threads one for receive data a another to write data in a file, three different class one to handle buttons that do some operations and initialization stuff, one class to receive the data and another class to write the data received.

One thread dealing with the data received, other thread dealing with the writing.

I have problems trying to make the signal of data received, then call the slot of data writing

Mainwindow.cpp

//Threads for write and receive usb transfer
    QThread *threadReceive = new QThread();
    QThread *threadWrite = new QThread();

    //Objects of calss receive and write
    receive *receive_usb = new receive();
    write *write_to_file = new write();

    //passing the usb handle deveice
    receive_usb->device_handle_receive=usb_channels->device_handle;

    //create the file ts
    write_to_file->create_file();

    //Move to threads
    receive_usb->moveToThread(threadReceive);
    write_to_file->moveToThread(threadWrite);

    //Strat the threads
    threadReceive->start();
    threadWrite->start();

    //When the buffer fills and emited the signal of receive write
    connect(receive_usb,SIGNAL(received(unsigned char*MPEG2_TS)), write_to_file, SLOT(write_to_file(unsigned char*MPEG2_TS)));

In the received class

#ifndef RECEIVE_H
#define RECEIVE_H
#include <libusb-1.0/libusb.h> //Include libsub
#include <QObject>

class receive: public QObject
{
    Q_OBJECT
public:
    receive();
    libusb_device_handle *device_handle_receive;

public slots:
    void transfer_usb(); //recieving tranfer from USB

private:
    //Creating the buffer to receive 245760 bytes= 240 Kb
    unsigned char MPEG2_TS[245760];

    //Variable to register the errors
    unsigned int error_receive;

    //Private function to emit the singal, receive parameter buffer
    void emitreceived(unsigned char *MPEG2_TS);

signals:
    //Signal emited
    void received(unsigned char *MPEG2_TS);

};

#endif // RECEIVE_H

receive.cpp

#include "receive.h"

receive::receive()
{

}

//-----------------------FUNCTION FOR USB RECEIVING BEGIN----------------

void receive::transfer_usb()
{
    while(1)
    {
    //It's a return of libusb_interrupt_transfer with the number of bytes that were transferred
    int transferred=0;

    //It's a return of libusb_interrupt_transfer return 0 if the transfer was successful
    int resultado=0;

    //Receiving Transfer
    resultado=libusb_interrupt_transfer (device_handle_receive,   //The device handle
                                    0x82,                 //Endponit 2
                                    MPEG2_TS,             //Buffer
                                    245760,               //Size of Buffer
                                    &transferred,         //Return the number of bytes transferred
                                    0                     //waiting time to receive the answer
                                  );

    if (resultado!=0) error_receive=10;   //For error 10: "Error in transfer in thread one"
    //Private function to emit the signal or received
    emitreceived(MPEG2_TS);
    }
}

//-----------------------FUNCTION FOR USB RECEIVING END------------------

//Private function t emit the signal
void receive::emitreceived(unsigned char *MPEG2_TS)
{
    emit received(MPEG2_TS);
}

Now in the write class i have

write.h

#ifndef WRITE_H
#define WRITE_H
#include <QFile>   //To use files
#include <QDataStream> //To stream to the file
#include <QObject>     //To use the Macro of Qobject

class write : public QObject
{
    Q_OBJECT
public:
    write();  //constructor
    //--------------FUNCTION TO CREATE A FILE BEGIN-------------
    void create_file(); //Create the File
    //--------------FUNCTION TO CREATE A FILE END---------------

public slots:
    void write_to_file(unsigned char *MPEG2_TS);  //Write to File

private:
    //--------------VARIABLES TO CREATE THE FILE BEGIN-----------
    QFile file;                                      //File to write the ts packets
    QDataStream out;                                 //To write in the file
    //--------------VARIABLES TO CREATE THE FILE END-------------
};

write.cpp

#include "write.h"

write::write()
{

}

void write::create_file()
{
    //Name of the file
    file.setFileName("data.ts");

    //Creation of the file, mode writeonly
    file.open(QIODevice::WriteOnly);
}

void write::write_to_file(unsigned char *MPEG2_TS)
{
    out.setDevice(&file); //to hadel the file writing

    for (unsigned int j=0;j<245760-1;j++)
    {
    out<<MPEG2_TS[j]; //Insert the bytte o he file
    }
}

When i debugging the program, the signal is not recognized

QObject::connect: No such signal receive::received(unsigned char*MPEG2_TS) in ../PIZZA_FILE/mainwindow.cpp:88

[mrjj]

@aurquiel said in Triying to create a custom signal with threads:

connect(receive_usb,SIGNAL(received(unsigned charMPEG2_TS)), write_to_file, SLOT(write_to_file(unsigned charMPEG2_TS)));

Hi
Only include the type, not parameter name
qDebug() << "status conn:" << connect(receive_usb,SIGNAL(received(unsigned char*)), write_to_file, SLOT(write_to_file(unsigned char*)));

[aurquiel]

yes it was that but my program doesn't do anything the file remains empty, can i pass the buffer through the signal emit to the slot?

There is a way to debug the threads to see the values of the variables that their change?

[mrjj]

@aurquiel
You can pass anything with the signal but maybe you can use a QString or QbyteArray as its known
how to copy/queue it. For a custom class/structure you must register it.
I think you need to use Qt::QueuedConnection for the connect.

[kshegunov]

If you're not stuck to Qt4, convert to the Qt5 connect syntax so you at least get compile-time checking of the signals and slots. Aside from that @mrjj is correct, you need to register whatever it is transfered between the threads (if not over a Qt::DirectConnection connection) as a metatype. Not only declare the type with Q_DECLARE_METATYPE, but actually register it at runtime with qRegisterMetatype<>.

[aurquiel]

I stop the threads, i just connect the signals and not moving that objects to a the thread, i put a break point in the receive class.

I am going to explain the code i have been writing

Three class "backend" "receive" "write", and the main window

I have a button in the main window with two connects

Minwindow.cpp

i have three objects for the three class

backend * usb_channels=new backend;
receive *receive_usb = new receive();
write *write_to_file = new write();

The connects

connect(ui->pushButton,SIGNAL(clicked()),usb_channels,SLOT(channel_521000_57856()));

this slot goes to a function in backend class i put a breakpoint there so the program goes there when a click the button

connect(ui->pushButton,SIGNAL(clicked()),receive_usb,SLOT(transfer_usb()));

Connect to a function in receive class that will emit the signal to write in the write class, put a break point in that function but is like the program doesn't use it nothing happends

An this connection will do that to write

connect(receive_usb,SIGNAL(received(QByteArray*)), write_to_file, SLOT(write_to_file(QByteArray*)));

Now i am using QByteArray and not threads.

Maybe there is a conflict for have multiplex connects to the same button, its like the program only recognize one connect the first one to backend function class, and not the second one to receive class. The Debug never cares about the breakpoint in the receive class in the function usb_transfeer()

[aurquiel]

I make it work, i just delete my building folder and build and.

It works with threads and for connect i could pass unsigned char in the connect

connect(receive_usb,SIGNAL(received(unsigned char*)), write_to_file, SLOT(write_to_file(unsigned char*)));

My file is filling with ts (transpor stream packets from the usb)