Can't implement CDC with HID

[yallxe]

I created a CDC and HID classes with one device

let mut hid = HIDClass::new_with_settings(
    &bus_allocator,
    KeyboardReport::desc(),
    10,
    HidClassSettings {  
        subclass: HidSubClass::NoSubClass,
        protocol: HidProtocol::Keyboard,
        config: ProtocolModeConfig::ForceReport,
        locale: HidCountryCode::NotSupported
    }
);
let mut serial = SerialPort::new(&bus_allocator);

let mut dev = UsbDeviceBuilder::new(&bus_allocator, vid_pid)
    .manufacturer("xkbd")
    .product("Prism80")
    .serial_number("000")
    .device_class(USB_CLASS_CDC)
    .build();

And the loop code:

loop {
    dev.poll(&mut [&mut serial, &mut hid]);
    if button_pin.is_high().unwrap() {
        hid.push_input(&report_struct).ok();
        led_pin.set_high().ok();
        serial.write(b"Pressed").ok();
    } else {
        hid.push_input(&null_report_struct).ok();
        led_pin.set_low().ok();
        serial.write(b"Released").ok();
    }

    // drop received data
    hid.pull_raw_output(&mut [0; 64]).ok();
}

However the USB device is not recognized by my PC, I tried the solution from #85 but it does not fix the issue and the device keep being unrecognized, how do I implement the HID with CDC?

[Disasm]

Do you have a dmesg log of failed enumeration? Are you using a release build?

[yallxe]

I don't, I'm kind of new to embedded developement and as far as I understand I need to have a debug probe to get this, maybe I understand it wrong.

P.S. I'm using Pi Pico.

[Disasm]

To get dmesg logs you need Linux (MacOS probably supports these as well).
By the way, does it work for you if you add only HID or only CDC?

[yallxe]

I'm on Windows currently, I can try WSL or use my laptop on linux and yes it does work with CDC or HID only.

[yallxe]

Just tested on my ubuntu, and... HID works, but I can't connect to serial port. I tried to connect using screen /dev/ttyACM1 115200 but I'm getting a [screen is terminating] error. However on Windows, things seems to be even worser, I don't really know how to check for errors and the device keep being unrecognized.

Also checked dmesg and usb device seems to be created with no errors.

[yallxe]

Forgot to answer, yes I'm using release build.

[Disasm]

Hmm, could you check if it works in Windows without .device_class(USB_CLASS_CDC)? Also it would be interesting to see USB capture (for example, gathered with Wireshark) which contains packets transferred when you connect to the device with screen.

[ianrrees]

I think one issue may be that you're calling serial.write() every time through the loop {}. In practice, doing one serial write will need >1 pass through the loop to finish, so I think eventually you'll have a problem with that approach. Maybe only send the message when the button level changes - something like this:

let mut last_state = button_pin.is_high().unwrap();
loop {
    // Poll stuff as above.  I'm not sure how HID works so maybe keep it as-is, maybe adapt as below

    let current_state = button_pin.is_high().unwrap();
    if last_state != current_state {
        last_state = current_state;
        if current_state {
            serial.write(b"Pressed").ok();
        } else {
            serial.write(b"Released").ok();
        }
}

[ianrrees]

I'd also leave out the line .device_class(USB_CLASS_CDC) - device class should probably be 0 (the default) which tells the host OS to figure out the class of each interface from its descriptors.

[yallxe]

I know about calling serial.write() every loop, fixed that already but didn't mention here, also removed .device_class(USB_CLASS_CDC) but it doesn't fix the problem.

[yallxe]

Okay, I managed to open serial monitor with screen, I was getting [screen is terminating] because I forgot to run as root. So basically, everything works fine on Linux, but not on Windows.

[ryan-summers]

What version of usb-device are you using? There was an enumeration bug on Windows that was fixed in the 2.9 release: https://github.com/rust-embedded-community/usb-device/blob/master/CHANGELOG.md

If you don't have that fix implemented, it's highly unlikely that your device will enumerate on Windows.

[mvirkkunen]

Have you tried adding interface association descriptors (IADs)? Windows is usually more picky about them than other OSs.

You can add them by removing device_class / device_subclass / device_protocol and just calling composite_with_iads() instead of them. Make sure your usbd_serial is also the newest version.

[yallxe]

Just updated usb-device to 0.2.9 and added composite_with_iads(), but still no results. Also made sure I'm using newest usbd-serial 0.1.1 and usbd-hid 0.6. Maybe something is wrong in my general code, so I'm also uploading it here.

P.S. The program is probably not crashing, because I can see the led light up when I'm pressing the button, the only thing that is not working is usb on Windows.

[yallxe]

Changing max_packet_size_0 to 16 instead of default 8 seems to fix the problem. Would be glad if somebody could explain me why was this occurring only on Windows, but as a problem is resolved, I'm closing the issue. Thanks everybody for the help.