I am working with USB devices that are used in Radio telescopes. The devices use a PIC micro-controller which is designed to sleep to minimize the clock noise unless a hardware error occurs or a host connects to its USB input. The MCU senses the Vdd on the USB connector as an indication of a host connection. In a remote application using a Raspberry Pi to control a number of these devices it is desirable to enable the raspberry controller to shut down the USB Vdd and allow the devices to go into sleep mode. Is there a way without rewiring the board to programmatically turn on/off the USB subsystem or just its Vdd?