/* register a callback for device status 
This function registers a callback for device status. The registered callback is used to report changes in the status of the device controller. */
static void usb_register_status_callback(usb_dc_status_callback cb)
/* register a callback for device status 
This function registers a callback for device status. The registered callback is used to report changes in the status of the device controller. */
static void usb_register_status_callback(usb_dc_status_callback cb)
{
	usb_dev.status_callback = cb;
}