Can you please take a trace of the USB traffic using any of the USB bus analyzers (like CATC/ Ellysis, etc). Attach the same here so that we can analyze.
Thank for your reply!
If I have a USB bus analyzers ,I think I needn't your help.
connect to the PC usb port ,computer found the device about 3 minutes later.
some quick,some slow,....
Did you run eye diagram to see how good the signal quality of the USB interface of your board is??
Do you have a FX2LP DVK? Did you try connecting one to your PC to see if it is not a issue with your PC??
Did you try it in other PCs to isolate whether it is a PC issue??