High density, low jitter, synchronous usb expansion

A method of providing expansion of a USB network, the method comprising:

• attaching a plurality of USB hubs to adjacent slots in a PXI instrumentation chassis;
• configuring one of said USB hubs as a primary USB Hub;
• connecting an upstream port of said primary USB Hub to a USB network;
• configuring a first downstream port of said primary USB Hub to communicate across a first PXI Local Bus to a first adjacent USB Hub of said plurality of USB Hubs other than said primary USB Hub, said first adjacent USB Hub being adjacent to said primary USB Hub;
• configuring a plurality of other downstream ports of said primary USB Hub to provide expansion of said primary USB Hub;
• connecting an upstream port of said first adjacent USB Hub to said first PXI Local Bus, wherein said first PXI Local Bus is in the direction of said primary USB Hub;
• and
• configuring a plurality of other downstream ports of said first adjacent USB Hub to provide expansion of the first adjacent USB Hub.

An apparatus for providing expansion of a USB network, comprising:

• a PXI or PXI-express form factor card;
• and
• USB hub circuitry comprising:
• an upstream port for receiving USB signals from either a first PXI local bus or a front panel connection of a USB Hub;
• a downstream USB port for expanding a USB network across a second PXI local bus;
• and
• one or more additional downstream USB ports for expanding said USB network.