>> >> Can I disable VBUS while keeping the rest of USB functional for a >> >> device that does not require bus power? >> > >> > unfortunately not, your device would see a disconnection. The reason is >> > that even though you don't really put any load on the bus, the PHY still >> > samples VBUS levels to know when the session is valid (VBUS > 4.4V). >> >> What if I use a USB cable with a separate DC input for the VBUS? > > What would be the point? I mean, if you've got a separate DC input for > Vbus then you aren't really saving any power or disabling anything. The point would be to minimize the amount of electrical noise the USB device is exposed to by using a low-noise supply for this such as a battery with a linear regulator. > If you did this and then turned off the separate DC power, your device > wouldn't work afterward. As Felipe pointed out, the device would think > the cable had been disconnected. Understood. Can you tell me how to disable VBUS on the USB hub/controller? I'll be attempting this on a Beaglebone. - Grant -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
