Technical Resource Hub

During compatibility testing, we have identified the following potential issues when using all-in-one screens and USB switchers.Outline of issues When using a USB switcher with active cable, it is possible to exceed the maximum number of USB Tiers (levels / hubs)The total permitted number of USB tiers is 7.  This is set out in the USB standard.  In theory, this limitation shouldn’t be reached, but as laptops develop and AV installations make greater use of USB devices, it is possible to exceed the limit.In our tested scenarios we used 2 different makes of Windows 11 laptops, 4 switches and 4 screens.- A laptop computer typically users 2 or 3 tiers, depending on complexity of internal USB.- A USB Switcher uses 2 tiers- An Active USB Cable uses 2 Tiers- An All-In-One screen with built-in camera, speakers and microphone will use 2 or 3 TiersSymptomsIf the total number of USB tiers is exceeded, Windows 11 machines will typically display an error message ‘USB device not recognised’ or ‘Maximum USB Hubs Exceeded’.  Occasionally, a “silent failure” will occur and no error is displayed.  However, in Device Manager, a USB Hub will be shown in fail state.USB devices on the All-In-One screen will not be accessible via the USB switch (microphone, camera, speakers and touch back). Fig 1.  In this scenario, the laptop will not see any of the peripherals on the AIO screen  How to determine if you have this issueWhilst you can check within Windows, we downloaded a USB Diagnostic tool to provide more detailed information.  There are lots available, but we used the Liteware USB20 Configurator app. Potential WorkaroundsBecause this is a fundamental restriction of USB architecture, there is no ideal solution.  However, options may include:Option 1.Using a passive USB connection to the laptop (USB-C