Add example code for generating USB key events and mouse events

[mutantbob]

I would like to use my Teensy4 to generate keypresses and mouse clicks. The C API is discussed at

https://www.pjrc.com/teensy/usb_keyboard.html

but I can not find an example in in the examples/ directory that shows how to do these sorts of things. I would like to read an example with a name like generate_usb_keypresses.rs, or generate_usb_mouse_events.rs to provide an overview similar to the pjrc docuentation.

[mciantyre]

Take a look at the usbd-hid package. The HID class lets us send keyboard and mouse events to a host. usbd-hid requires a USB bus implementation, and we can use the USB driver in the imxrt-usbd package for that implementation. Here's an example of how to generate mouse events from a Teensy 4.

imxrt-usbd isn't part of the BSP, since the BSP has a separate USB driver for logging / serial. Nevertheless, users can pair the BSP and imxrt-usbd in their build if they disable the BSP's usb-logging feature. I'll add examples here once the existing USB driver is removed (#95).

[mutantbob]

I have managed to copy the mouse code from the example you linked, and got it working in my app.

Unfortunately, I have not yet figured out how to generate keyboard events. I have added a comment to https://github.com/twitchyliquid64/usbd-hid/issues/16 , but since the issue is closed it might not get noticed.

[mciantyre]

Thanks for troubleshooting that keyboard example.

Readers who are interested in seeing a keyboard demo before it's available in this repo should see imxrt-rs/imxrt-usbd#14.

[mciantyre]

Now that imxrt-hal has in-repo hardware examples, I plan to reduce the number of hardware examples maintained here. By contributing hardware examples to imxrt-hal, we'll be able to use them across multiple boards.

Teensy 4 users can still refer to the keyboard demo linked above for a demonstration. If users want that example ported to more i.MX RT boards, open an issue in imxrt-hal.