Make a Qtconcurrent thread for a USB communication between computer and microcontoller

[jim53]

Hello,

I have written a Qt software that communicate with a microcontroller by USB.
I want to put the function pollUSB in a separate thread to avoid frozen of the GUI. I have read that it is possible using Qtconcurrent but I don't how I have to do that in my case because the function pollUSB is not directly in the main.cpp file.

My software is structured like this :
Main.cpp : Contain the main function and the instanciation of a GUI object define by a specific class.
This GUI class instanciate USB communication object from anioher class (USB class).
And finaly, the function pollUSB is amember funciton of this USB Class.

I don't where and how i have to write the line :
@Qfuture <void> future = Qtconcurent::run(???)@

Could someone now and help me to solve my problem. Thank you for advance.

[SGaist]

Without more information from your side it's difficult to help. From your description you should probably use a worker object with QThread which is described in the documentation.

[kuzulis]

bq. I have written a Qt software that communicate with a microcontroller by USB.

In a common case, there are not need to use threads for this, since OS (as Windows, as Linux and so on) provides async API to communicate with USB directly (to read/write endpoints and so on).

[Vincent007]

see whether it helps you.
https://github.com/bimetek/QUSB

[Francknos]

Hi, I use this for my communication with usb device.

For me I launch at the end of constructor of my GUI

something like that

@
...//constructor end
QtConcurrent::run(Caller class (this), &MyClass::threadedFunction, parameters);
@

You have to put threadedFunction as slot on your MyClass

if you want to send a parameters to threadedFunction you can make someThing like this:

@
public slot:
void threadedFunction(Parameters );

// ....

Parameters b;
QtConcurrent::run(this, &MyClass::threadedFunction, b);
@

To keep hands of "thread" you need to get an handle in FutureWatcher to stop your thread if it runs while(1).

Good luck ...

[jim53]

Thank you very much for all reply but I still still do not understand how integrate the thread for HID_PnP::PollUSB() function in my code. You could find below my files. Thank you for help if you know where and how write code to make a thread for function HID_PnP::PollUSB() :

*main.cpp : *
@#include <QApplication>
#include "usb_motor_control_app.h"

int main(int argc, char *argv[])
{
QApplication a(argc, argv);
USB_Motor_Control_App w;
w.show();
return a.exec();
}@

usb_motor_control_app.h :
@#ifndef USB_MOTOR_CONTROL_APP_H
#define USB_MOTOR_CONTROL_APP_H

#include <QMainWindow>
#include "hid_pnp.h"

namespace Ui {
class USB_Motor_Control_App;
}

class USB_Motor_Control_App : public QMainWindow
{
Q_OBJECT

public:
explicit USB_Motor_Control_App(QWidget *parent = 0);
~USB_Motor_Control_App();

private:
Ui::USB_Motor_Control_App *ui;
HID_PnP *plugNPlay;

public slots:
void update_gui(bool isConnected, bool isPressed, int potentiometerValue);

signals:
void toggle_leds_button_pressed(); //Exemple de base
void start_button_pressed();
void stop_button_pressed();

private slots:
void on_pushButton_clicked(); //Exemple de base
void onpButton_start_clicked();
void onpButton_stop_clicked();
void onrButton_limited_rotation_clicked();
void onrButton_Continuous_rotation_clicked();

};

#endif // USB_MOTOR_CONTROL_APP_H@

hid_pnp.h :
@#ifndef HID_PNP_H
#define HID_PNP_H

#include <QObject>
#include <QTimer>
#include "../HIDAPI/hidapi.h"

#include <wchar.h>
#include <string.h>
#include <stdlib.h>
#include "define.h"

class HID_PnP : public QObject
{
Q_OBJECT
public:
explicit HID_PnP(QObject *parent = 0);
~HID_PnP();

signals:
void hid_comm_update(bool isConnected, bool isPressed, int potentiometerValue);

public slots:
void toggle_leds();
void PollUSB();

private:
bool isConnected;
bool pushbuttonStatus;
bool toggleLeds;
int potentiometerValue;

hid_device *device;
QTimer *timer;
unsigned char hid_buffer[HID_BUFFER_SIZE];

void CloseDevice();

};

#endif // HID_PNP_H
@

[SGaist]

What does PollUSB do ?

[jim53]

You could fin below the code of PollUSB()

@void HID_PnP::PollUSB()
{
hid_buffer[0] = 0x00;
memset((void*)&hid_buffer[2], 0x00, sizeof(hid_buffer) - 2);

if (isConnected == false) {
    device = hid_open(BOARD_PID, BOARD_VID, NULL);

    if (device) {
        isConnected = true;
        hid_set_nonblocking(device, false);             //Initialement à true
        timer->start(15);
    }
}
else {
    if(toggleLeds == true) {
        toggleLeds = false;

        hid_buffer[1] = TOGGLE_LED;

        if (hid_write(device, hid_buffer, sizeof(hid_buffer)) == -1)
        {
            CloseDevice();
            return;
        }

        hid_buffer[0] = 0x00;
        hid_buffer[1] = READ_POTENTIOMETER_VALUE;
        memset((void*)&hid_buffer[2], 0x00, sizeof(hid_buffer) - 2);
    }

    if (hid_write(device, hid_buffer, sizeof(hid_buffer)) == -1)
    {
        CloseDevice();
        return;
    }
    if(hid_read(device, hid_buffer, sizeof(hid_buffer)) == -1)
    {
        CloseDevice();
        return;
    }
    if(hid_buffer[0] == READ_POTENTIOMETER_VALUE) {
        potentiometerValue = (hid_buffer[2]<<8) + hid_buffer[1];
        hid_buffer[1] = READ_PUSH_BUTTON_STATUS;
    }
    else if(hid_buffer[0] == READ_PUSH_BUTTON_STATUS) {
        pushbuttonStatus = (hid_buffer[1] == 0x00);
        hid_buffer[1] = READ_POTENTIOMETER_VALUE;
    }
}

hid_comm_update(isConnected, pushbuttonStatus, potentiometerValue);

}@

[jim53]

I add the code of the constructor of the HID_PnP class :

@HID_PnP::HID_PnP(QObject *parent) : QObject(parent) {
isConnected = false;
pushbuttonStatus = false;
potentiometerValue = 0;
toggleLeds = 0;

device = NULL;
hid_buffer[0] = 0x00;
hid_buffer[1] = READ_POTENTIOMETER_VALUE;
memset((void*)&hid_buffer[2], 0x00, sizeof(hid_buffer) - 2);

timer = new QTimer();
connect(timer, SIGNAL(timeout()), this, SLOT(PollUSB()));

timer->start(250);

}@