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Hi, Don't know if it is proper to post here.
Currently I'm on a project with USB HID function. The function works well without any error except that the USB HID has speed vary issue. The speed will vary depending on host PCs.
Using USB View, I found that for fast speed, the device has been assigned to be controlled by USB2 Enhanced Host Controller(EHC) Full Bus Speed, however, for slow speed, the device has been assigned to be controlled by USB Universal Host Controller(UHC) Full Bus Speed(Same Hardware&Firmware).
The confusing thing is what makes the host controller decides that the device should be assigned to be controlled by EHC or UHC.
Any idea and suggestions for this issue?
Thanks.
Generally EHCI can only handle high-speed devices while companion controller OHCI or UCHI can only handle full/low speed devices this of course applies for a single root HUB, of course your PC can have more root HUB which have their own collection of controllers.