Hopefully someone with some expert USB knowledge can help me. I have a 4 port USB 2.0 hub that is using an Alcor AU6254 microcontroller. The 4 port hub is comprised of two boards -a Main board and a daisy chained secondary board. Two ports on each board. Each board has the same microncontroller.

When certain HID devices are plugged into either of the ports of the secondary board the secondary board loses HID (mouse, keyboard, etc) connectivity. In other words HID components won't work in the ports of the secondary board, but will work in ports of the main board. Standard USB components (flash drives, etc) will work in any of the 4 ports.

The error state resets if the main USB cable to the hub is unplugged/re-plugged.

The only difference I have observed with the HID device that triggers the error condition is that it uses more power (~250 mA) than other devices like a keyboard or mouse.

It seems that the microcontroller should perform a reset but isn't.

All voltages and currents are within spec

Any thoughts on a cause?