The article addresses issues where a computer does not recognize a connected KNX/USB interface, detailing causes such as faulty USB cables or ports, Windows sleep mode interference, and improper KNX bus connection. Solutions include switching USB ports, installing a KNX USB fix, and verifying proper KNX bus connection and power supply.
Problem
Although the computer has been connected with the KNX/USB interface, it is not recognized. The following cases can be distinguished:
Case 1 - USB cable or USB port issue
The USB cable between the computer and the KNX/USB interface is broken and/or the connected USB port is defective (or it does not deliver enough power or has some non-standard chipset with special driver)
Resolution
The following shall be done:
Unplug the USB cable from the currently connected USB port and plug it to another USB port from the same computer.
Unplug the USB cable from the currently connected USB port and plug it to a USB port from another computer.
Case 2 - Windows 8.1, Windows 10 or Windows 11 sleep mode
Since Windows 8.1 KNX/USB interface issues can occur because of:
The automatic sleep mode of USB ports
The automatic sleep mode of the operating system (e.g. when closing the notebook lid)
Resolution
The solution is to install the KNX USB fix that prevents Windows to go into sleep mode for any connected KNX/USB interface.
Requirements
Windows 8.1, Windows 10 or Windows 11
Administrative rights
For Case 1
Follow this procedure:
Install the KNX USB fix, and repeat for each extra connected KNX/USB interface
Restart Windows
For Case 2
Follow this procedure:
Install the fix, and repeat for each extra connected KNX/USB interface
Unplug and re-plug the KNX/USB interface once after Windows 8.1/10/11 wake-up
Case 3 - The KNX/USB interface is not connected to the bus
- The KNX/USB interface is not connected to the KNX bus
- The KNX bus has no power
- The bus connections' polarity is reversed
Resolution
Connect the KNX/USB to the KNX bus correctly and verify that the connection's polarity is not reversed. Moreover, verify that the KNX power supply is supplying sufficient power to the KNX bus.
If none of the above solutions resolved the issue, then please report it as described here.