case USB_INSERTED:
                /* inject an event into the button queue so the main thread
                 * will run the USB-UI code and return after the desired
                 * drivers are enabled */
                usb_state = USB_POWERED;
                queue_send(&button_queue, SYS_USB_ATTACHED, NULL);
                break;



==============================================


case SYS_USB_ATTACHED:
#ifdef USB_ENABLE_STORAGE
            usb_core_enable_driver(USB_DRIVER_MASS_STORAGE, false);
#endif
#ifdef USB_ENABLE_HID
            usb_core_enable_driver(USB_DRIVER_HID, false);
#endif
#ifdef USB_ENABLE_CHARGING_ONLY
            usb_core_enable_driver(USB_DRIVER_CHARGING_ONLY, false);
#endif
            usb_core_enable_driver(USB_DRIVER_MTP, true);
            return 1;