USB preamble PID problem

usb preamble

thanks to your help i could set up the HUB i'm using.
I'm using usb host cypress sl811hs connected to atmel's hub at43301;
now i have a problem to communicate to a slow speed device (mouse) connected to the hub

this is what i do :
get device descriptor of the hub
get configuration descriptor
set configuration (led goes green)
power port 1
reset port 1 (mouse is connected to port1. At this point, its led goes red, meaning keep alive signals are being sent from the hub. untill here, no problem)

then, i'd like to set adress 1 to the mouse.
what i do is configuring the SL811HS to send PRE PID before sending set adress packets. It does so (checked on the scope)
BUT, i always a time out error (no respond from the HUB) then the sl811hs stop sending keep alive packets (hub's led turn off, hub's no more configurated) and i can't do anything but reseting the sl811hs.


Can you see what i'm doing wrong ? (in the sequence, or in the requests)
Do you know if the problem comes from the sl811hs or from the hub ?

thanks for your help