Troubleshooting USB Communication with Qt and libusb for Embedded Device Recognition

[Andrew23]

I have an embedded USB device called 'Cruise Dongle USBP' with VID 0x0001 and PID 0x0002 (these values are just for testing) for which I loaded the WinUSB driver using Zadig.


Now I want to communicate with this device in Qt using the libusb library, but when I search for it, the library cannot find it.

void USBDevice::ScanUsbDevices()
{
    libusb_context *ctx = nullptr;
    libusb_device **device_list = nullptr;
    ssize_t count;

    if (libusb_init(&ctx) != 0) {
        qWarning() << "Error initializing libusb";
    }

    // Get the device list
    count = libusb_get_device_list(ctx, &device_list);

    if (count < 0) {
        usbList->addItem("Error: Unable to get the device list.");
        libusb_exit(ctx);
        return;
    }

    qDebug() << "USB devices found:" << count;

    // usbList->addItem(QString("USB devices found: %1").arg(count));

    // Iterate over the found devices
    for (ssize_t i = 0; i < count; i++) {
        libusb_device *device = device_list[i];
        libusb_device_descriptor desc;

        if (libusb_get_device_descriptor(device, &desc) == 0) {
            QString info = QString("VID: 0x%1 PID: 0x%2")
            .arg(desc.idVendor, 4, 16, QChar('0'))
                .arg(desc.idProduct, 4, 16, QChar('0'));

            // Try to open the device to read extra information
            libusb_device_handle *handle;
            if (libusb_open(device, &handle) == 0) {
                unsigned char buffer[256];

                if (desc.iManufacturer && libusb_get_string_descriptor_ascii(handle, desc.iManufacturer, buffer, sizeof(buffer)) > 0) {
                    info += " | Manufacturer: " + QString::fromUtf8(reinterpret_cast<char*>(buffer));
                }

                if (desc.iProduct && libusb_get_string_descriptor_ascii(handle, desc.iProduct, buffer, sizeof(buffer)) > 0) {
                    info += " | Product: " + QString::fromUtf8(reinterpret_cast<char*>(buffer));
                }

                libusb_close(handle);
            }

            // usbList->addItem(info);
            qDebug() << info;
        }
    }

    // Free the device list
    libusb_free_device_list(device_list, 1);
    libusb_exit(ctx);
}

that returns

AllK required contiguous memory = 675016 (64bit)
  8 HotK Handles: HandleSize 2112 PoolSize 16912 (bytes)
  64 LstK Handles: HandleSize 64 PoolSize 4112 (bytes)
  2048 LstInfoK Handles: HandleSize 64 PoolSize 131088 (bytes)
  128 UsbK Handles: HandleSize 96 PoolSize 12304 (bytes)
  64 DevK Handles: HandleSize 112 PoolSize 7184 (bytes)
  2048 OvlK Handles: HandleSize 104 PoolSize 213008 (bytes)
  64 OvlPoolK Handles: HandleSize 96 PoolSize 6160 (bytes)
  32 StmK Handles: HandleSize 176 PoolSize 5648 (bytes)
  2048 IsochK Handles: HandleSize 136 PoolSize 278544 (bytes)

Dynamically allocated as needed:
	KLST_DEVINFO = 2596 bytes each
USB devices found: 6
"VID: 0x8086 PID: 0xa36d"
"VID: 0x8087 PID: 0x0aaa"
"VID: 0x10de PID: 0x1ada"
"VID: 0x0b05 PID: 0x1866 | Manufacturer: ASUSTeK Computer Inc. | Product: N-KEY Device"
"VID: 0x046d PID: 0xc01e | Manufacturer: Logitech | Product: USB-PS/2 Optical Mouse"
"VID: 0x1366 PID: 0x1050"

I have tried reinstalling the drivers and changing them to Klibusb or others, but nothing works. Can anyone give me some advice?

[jsulm]

@Andrew23 libusb is not part of Qt, you should consider asking there

[JoeCFD]

And is it a better choice to use native Windows code to do the same job?

[Andrew23]

@jsulm said in Troubleshooting USB Communication with Qt and libusb for Embedded Device Recognition:

@Andrew23 libusb is not part of Qt, you should consider asking there

Yes, I know, but I thought that maybe someone had encountered the same issue while implementing a Qt application that uses the libusb library.

@JoeCFD said in Troubleshooting USB Communication with Qt and libusb for Embedded Device Recognition:

And is it a better choice to use native Windows code to do the same job?

What do you mean? Sorry, but I’m a beginner in implementing USB communication between a device and an application.

[JoeCFD]

@Andrew23 Try to use Qt serial port to detect USB Devices

#include <QCoreApplication>
#include <QSerialPortInfo>
#include <QDebug>

int main(int argc, char *argv[])
{
   QCoreApplication a(argc, argv);

   // List all available serial ports
   QList<QSerialPortInfo> ports = QSerialPortInfo::availablePorts();
   foreach (const QSerialPortInfo &port, ports) {
       qDebug() << "Port:" << port.portName();
       qDebug() << "Description:" << port.description();
       qDebug() << "Manufacturer:" << port.manufacturer();
       qDebug() << "Vendor ID:" << port.vendorIdentifier();
       qDebug() << "Product ID:" << port.productIdentifier();
       qDebug() << "-----------------------------------";
   }

   return a.exec();
}

Open and Communicate with the USB Device

#include <QCoreApplication>
#include <QSerialPort>
#include <QSerialPortInfo>
#include <QDebug>

int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);

    // Create a serial port object
    QSerialPort serial;

    // Configure the serial port
    serial.setPortName("COM3"); // Replace with your device's port name
    serial.setBaudRate(QSerialPort::Baud9600);
    serial.setDataBits(QSerialPort::Data8);
    serial.setParity(QSerialPort::NoParity);
    serial.setStopBits(QSerialPort::OneStop);
    serial.setFlowControl(QSerialPort::NoFlowControl);

    // Open the serial port
    if (serial.open(QIODevice::ReadWrite)) {
        qDebug() << "Connected to" << serial.portName();

        // Write data to the device
        QByteArray data = "Hello, USB Device!";
        serial.write(data);
        qDebug() << "Data sent:" << data;

        // Read data from the device
        if (serial.waitForReadyRead(5000)) { // Wait for 5 seconds
            QByteArray response = serial.readAll();
            qDebug() << "Response:" << response;
        } else {
            qDebug() << "Timeout: No response from device.";
        }

        // Close the serial port
        serial.close();
    } else {
        qDebug() << "Failed to open port" << serial.portName();
    }

    return a.exec();
}

If the code above does not work for you, try to find Windows API

#include <windows.h>
#include <setupapi.h>
#include <iostream>
#include <string>
#include <vector>
#include <iomanip>

#pragma comment(lib, "setupapi.lib")

// Function to convert a wide string to a std::string
std::string WideStringToString(const std::wstring& wideStr) {
    if (wideStr.empty()) return std::string();
    int sizeNeeded = WideCharToMultiByte(CP_UTF8, 0, &wideStr[0], (int)wideStr.size(), nullptr, 0, nullptr, nullptr);
    std::string str(sizeNeeded, 0);
    WideCharToMultiByte(CP_UTF8, 0, &wideStr[0], (int)wideStr.size(), &str[0], sizeNeeded, nullptr, nullptr);
    return str;
}

// Function to enumerate USB devices
void EnumerateUSBDevices() {
    HDEVINFO deviceInfoSet;
    SP_DEVINFO_DATA deviceInfoData;
    DWORD deviceIndex = 0;

    // Initialize the device information set for USB devices
    deviceInfoSet = SetupDiGetClassDevs(&GUID_DEVCLASS_USB, nullptr, nullptr, DIGCF_PRESENT | DIGCF_PROFILE);
    if (deviceInfoSet == INVALID_HANDLE_VALUE) {
        std::cerr << "Failed to get device information set." << std::endl;
        return;
    }

    // Initialize the device information structure
    deviceInfoData.cbSize = sizeof(SP_DEVINFO_DATA);

    // Enumerate through all devices in the set
    while (SetupDiEnumDeviceInfo(deviceInfoSet, deviceIndex++, &deviceInfoData)) {
        // Get the device instance ID (contains VID and PID)
        wchar_t deviceID[256];
        if (SetupDiGetDeviceInstanceId(deviceInfoSet, &deviceInfoData, deviceID, sizeof(deviceID) / sizeof(deviceID[0]), nullptr)) {
            std::wstring deviceIDStr(deviceID);
            std::string deviceIDUtf8 = WideStringToString(deviceIDStr);

            // Extract VID and PID from the device instance ID
            size_t vidPos = deviceIDUtf8.find("VID_");
            size_t pidPos = deviceIDUtf8.find("PID_");
            if (vidPos != std::string::npos && pidPos != std::string::npos) {
                std::string vid = deviceIDUtf8.substr(vidPos + 4, 4);
                std::string pid = deviceIDUtf8.substr(pidPos + 4, 4);

                std::cout << "Device ID: " << deviceIDUtf8 << std::endl;
                std::cout << "VID: " << vid << ", PID: " << pid << std::endl;
            }
        }

        // Get the device description
        wchar_t deviceDescription[256];
        if (SetupDiGetDeviceRegistryProperty(deviceInfoSet, &deviceInfoData, SPDRP_FRIENDLYNAME, nullptr, (PBYTE)deviceDescription, sizeof(deviceDescription), nullptr)) {
            std::wstring descriptionStr(deviceDescription);
            std::string descriptionUtf8 = WideStringToString(descriptionStr);
            std::cout << "Description: " << descriptionUtf8 << std::endl;
        }

        std::cout << "-----------------------------------" << std::endl;
    }

    // Clean up
    SetupDiDestroyDeviceInfoList(deviceInfoSet);
}

int main() {
    EnumerateUSBDevices();
    return 0;
}

[Andrew23]

@JoeCFD said in Troubleshooting USB Communication with Qt and libusb for Embedded Device Recognition:

@Andrew23 Try to use Qt serial port to detect USB Devices

Maybe I didn't explain my context well. What you suggested is to open a serial connection with QSerialPort, but my USB device is not a CDC-ACM class device that creates a virtual COM port. My goal is to communicate with my USB device through bulk transfer, reading/writing to its endpoints. I know that implementing a driver for this purpose is usually necessary, but I have discovered that it is possible to use the generic WinUSB driver with the libusb library. Am I wrong?