The USBD peripheral on the nRF52840 contains a series of registers, called EVENTS registers, that indicate the reason for entering the USBD event handler. These events must be handled by the application to complete the enumeration process.
In this starter code the USBD peripheral is initialized in `init` and a task, named `main`, is bound to the interrupt signal USBD. This task will be called every time a new USBD event needs to be handled. The `main` task uses `usbd::next_event()` to check all the event registers; if any event is set (occurred) then the function returns the event, represented by the `Event` enum, wrapped in the `Some` variant. This `Event` is then passed to the `on_event` function for further processing.
✅ Go to `fn on_event`, line 39. In this section you'll need to implement the following USB events `USBRESET` and `EP0SETUP` so that your log output will look like this:
-`USBRESET`. This event indicates that the host issued a USB reset signal. According to the USB specification this will move the device from any state to the `Default` state. Since we are currently not dealing with any other state, you can handle this state by adding a log statement to provide information that this event occurred.
-`EP0DATADONE`. The USBD peripheral is signaling the end of the DATA stage of a control transfer. Since you won't encounter this event just yet, you can leave it as it is.
-`EP0SETUP`. The USBD peripheral has detected the SETUP stage of a control transfer. Add a log statement containing "goal reached; move to the next section" and exit the application.