Leopard board is configured as USB device mode by default.
With current version of Leopard board (1.0), there is no jumper to set it to host mode.
A quick and dirty fix is to wire USB_ID to ground (schematic page 5), and connect 5V power to USB_VBUS.
Then the Leopard board is forced to host mode.
Jumpers will be added in next version to switch to both host mode and device mode easily.