Problem

Although the computer has been connected with the KNX/USB interface, it is not recognized. The following cases can be distinguished:

1. Case 1 - USB cable or USB port issue
2. Case 2 - Windows 8.1, Windows 10 or Windows 11 sleep mode
3. Case 3 - The KNX/USB interface is not connected to the bus

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:

1. The automatic sleep mode of USB ports
2. The automatic sleep mode of the operating system (e.g. when closing the notebook lid)

Resolution

The solution is to install a 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 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.