"This device cannot start." Message in Device Manager with USB SerialHardware: Instrument Connectivity Other>>USB>>USB-485/4, Instrument Connectivity Other>>USB>>USB-232, Instrument Connectivity Other>>USB>>USB-485, Instrument Connectivity Other>>USB>>USB-485/2, Instrument Connectivity Other>>USB>>USB-232/2, Instrument Connectivity Other>>USB>>USB-232/4, GPIB>>External Controllers/Convertors>>USB-488
Problem: I have multiple USB hubs in my system chained together and my USB-485 or USB-232 fails to enumerate when plugged into the end of the hub chain or I get a "This device cannot start." message in the Device Manager. Solution: USB uses a tier topology where the USB host controller (and root hub) is located in the first (highest) USB tier, and each USB hub resides on a lower tier. For example, when three USB hubs are chained together and connected to the USB root hub, the third USB hub resides in the 4th USB tier. USB only supports 7 tier levels, thus if any devices (including hubs) reside in tiers lower than 7, they will not enumerate correctly. In addition, USB hardware may contain internal USB hubs (compound) and/or consist of multiple devices (composite). In this case, the hardware must reside in tiers higher than 7 for all of the internal components to enumerate correctly. The USB-232/2 and USB-485/2 are composite devices, and must be plugged into a USB hubresiding at tier 6 or higher. The USB-232/4 and USB-485/4 are compound composite devices, and must be plugged into a USB hub residing at tier 5 or higher. Related Links: Attachments:
Report Date: 07/09/2002 Last Updated: 09/08/2004 Document ID: 2N8IMLYF |
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