12.3.3 I Have Connected My Tool Through a USB Hub, and Now I Get Error Messages and Inconsistent Results While Programming and Debugging

Tools and devices may be connected directly to a USB port on your debugging PC. If this is not an option, you may reduce/eliminate problems by:

Disconnect any other USB devices connected to the hub
Switch ports on the USB hub
Set the tool clock frequency low. E.g., Set JTAG Clock < 600 kHz.
If Use external reset is an option for your tool/device combination, enable this

Note: The AVR Dragon may connect through a powered USB hub because the power supply on the Dragon can be too weak if the motherboard does not provide enough power. The hub might be of too low quality if the Dragon times out or freezes.