USB commands

Hi all, I am playing around with the USB commands in SIMTrace but I'm having a bit of trouble. I wrote a short python script to send a GET_VERSION command. However, only the first one is received by the board. If I run it, the first time I will see a GET_VERSION in the debug terminal. If I try again, however many times, I do not see any output. Why is this? The script: ---snip--- #!/usr/bin/python import usb.core import usb.util cmd="\x01\x00\x00\x00" dev=usb.core.find(idVendor=0x16c0, idProduct=0x0762) dev.set_configuration() dev.write(1, cmd, 0) ---snip---