Maximum number of usb devices - kylessukaichang/kylessukaichang.github.io GitHub Wiki

  • Windows Error When Plugging In Multiple NI USB Devices

    • Solution
      • USB host controllers are designed to support a limited number of USB endpoints. If the number of endpoints connected exceeds the number supported by the USB host controller on your computer, Windows will throw an error indicating that the controller does not have sufficient resources for the device.
      • The number of endpoints used by NI USB devices is not adjustable. Try the following steps to resolve the error:
        • Unplug any USB devices that are not necessary for your application.
        • Connect NI USB devices directly to the computer, rather than through a USB hub or extender.
        • Distribute your USB devices evenly across multiple root ports or host controllers.
        • You can see your computer’s available and installed host controllers in Windows Device Manager.
        • If your computer has PCI, PCIe, or other types of expansion slots, you may be able to add additional host controllers with USB adapter cards.
        • If you can replace the USB host controller on your computer, try a different chipset or brand.

  • Hardware limitations on USB endpoints (XHCI)

    • windows 8 is able to support at least 18 connected devices, plus several hubs.
    • Debian systems, however, have issues at about 12 devices and we see that the XHCI driver is reaching its endpoint limitation.
    • We guess that this limitation is 64 endpoints (since hubs can consume 4 or 5 endpoints each)

  • Getting Around USB3 xhci 32 Device Limit "Max number of devices this xHCI host supports is 32"

    • Wait, you're saying, but USB should support 127 devices (which include hub ports), why only 32?
    • Well, xhci/USB3 actually has an extra limit of 96 endpoints and each device uses 3 endpoints, which leaves you with only 32 devices. Yes, this is terrible, I agree. It's also not well documented and few people know how to get around it.