Why is usb hid getting slow speed?

[DQUY05]

Hello !

I am using hid_device, to read data from incoming usb port (this data I get is transmitted by mcu)
Here is my receive interrupt function, it works fine, but only at 10ms 1 time,

QObject::connect(this,SIGNAL(hiddataarrived(unsigned char *, unsigned char)),this,SLOT(Outdata(unsigned char *, unsigned char)));

void MainWindow::Outdata(unsigned char *data, unsigned char length)  // slot
{
    QString chuoi;
    for(int i=0;i<length;i++)
    {
        chuoi.append(data[i]);
    }
    ui->textEdit_2->append(chuoi);  // show on textedit
}

when i increase the speed between transmissions, about 5ms 1 time, some data is lost
Is it because the show function on textedit makes it late? or what is the reason?

Thank you !

[Christian Ehrlicher]

@DQUY05 said in Why is usb hid getting slow speed?:

hiddataarrived

Where does this signal comes from? It's not a Qt signal and we don't know what it does/where it comes from.

[SGaist]

@DQUY05 said in Why is usb hid getting slow speed?:

void MainWindow::Outdata(unsigned char *data, unsigned char length) // slot
{
QString chuoi;
for(int i=0;i<length;i++)
{
chuoi.append(data[i]);
}
ui->textEdit_2->append(chuoi); // show on textedit
}

Hi,

Beside the information requested by @Christian-Ehrlicher, this loop is unnecessary. QString can be built taking a char * and a length. Check the fromXXX methods.

[DQUY05]

@Christian-Ehrlicher
Here is the signal constructor, the interrupt occurs every time there is data from the usb port (64 bytes), and if I remove the command QCoreApplication::processEvents();
the program freezes

void MainWindow::run()
{
    int res,i;
    unsigned char buf1[64];

    while(isopen==1)
    {
        res=hid_read(target, buf1, 64);   // read data from usb_hid
        if(res==-1)     // if an error occurs 
        {
           isopen=0;
           ui->listWidget->clear();
           ui->pushButton_2->setText("Not connect");
        }
        else if(res==0) // No data
        {}
        else  //if(res>0)
        {
            unsigned char datas[64];

            for(i=0;i<64;i++)
            {
                datas[i]=buf1[i];
            }

            emit hiddataarrived(datas,64);
        }
        QCoreApplication :: processEvents ();   //avoid freezing 
    }
}

The receive interrupt speed I need it to achieve at 100us per 64 byte transmission, but currently only 10ms per 64 byte transmission, as the baud rate increases, the data will be interrupted

Thanks!

[DQUY05]

@SGaist said in Why is usb hid getting slow speed?:

QString can be built taking a char * and a length

Dear Sir !

Sorry, I'm newbie, and my English is not very good, you mean QString::fromUtf8(data,length);
I tried, but I don't know if this is correct, but I don't get a QString

void MainWindow::Outdata(const char *data, unsigned char length) // slot
{
QString chuoi;
//    for(int i=0;i<length;i++)
//    {
//        chuoi.append(data[i]);
//    }
chuoi=QString::fromUtf8(data,length);
ui->textEdit_2->append(chuoi); // show on textedit
}

I don't know how to use this structure, is it because my loop is late and lose data?

Many thanks!

[Christian Ehrlicher]

@DQUY05 said in Why is usb hid getting slow speed?:

hid_read

When this is a blocking function than you must not do this in the main thread. Move this out into another thread.
And only reading 64 bytes at once can not be "fast".

[DQUY05]

@Christian-Ehrlicher
Thank you,
I am using libusb (usb_hid), and also know the max speed is about 64Kbyte/s, here mine is 64Byte/5ms = 12.5Kbyte/s, anyway my project will accept working at this speed.

When this is a blocking function than you must not do this in the main thread. Move this out into another thread.

Sorry, I don't know how?

Many thanks!

[SGaist]

Since you are pretty new to all of this, you might want to consider using a library wrapping libusb for Qt.

On a side note, many MCUs have serial port to communicate with which is usually way simpler to use. Is it not the case of yours ?

[DQUY05]

@SGaist
Thank you !

Since you are pretty new to all of this, you might want to consider using a library wrapping libusb for Qt.

You are right, I am using this set of libraries.

On a side note, many MCUs have serial port to communicate with which is usually way simpler to use. Is it not the case of yours ?

Serial port I have successfully done, however it is asynchronous communication, and the speed is usually lower than usb_hid, in this project of mine, which requires using usb_hid, I have increased the speed to 25Kbyte/s, and got the desired result, please write to solve the problem, in the future if anyone can increase the speed, hope to have development

Regards !