DE2 board USB communication

hello

I am now working in a project which needs to make the DE2-70 board as a USB device and the host is the PC.

I write some codes in vhdl to communicate with the ISP1362, because I can not to use the NIOS processor...

When I try to probe the system, I found these problems:

1) If I connect both the blaster cable and the device cable to the pc or only the blaster, the host

shows initially the blaster, then I download the firmware to the FPGA and the system do the Enumeration and initialization

process and the ISP1362 is recognize by the host PC. But, if I disconnect the blaster cable, the system

is not respond, then I reset the driver by the firmware and the device is doesn't show by the host.

I am using the VISA USB Raw of National Instrument and its driver in the host.

2) If I work with both the blaster cable and the device cable connected, the system can transmit data

from PC to device successful, but when I try to send data from device to host PC, it show me a timeout error. I check the firmware step by step and it apparently work correctly.

Could you help me with these????