Other Parts Discussed in Thread: TPS3823
Customer is using the TUSB8020B USB 3.0 2 port hub in an embedded design (not a stand alone hub) and they cannot get hot plug to work. I am not entirely convinced that this is the hubs problem, possibly it's an issue with the USB drive on the host CPU.
If the USB devices connected to the down stream ports of the hub are plugged in and have power, they are correctly enumerated by the host when the USB driver loads during the host boot time.
However, if the devices are removed, there is no change in the registration.
If the devices are plugged in after the USB driver has loaded, then the devices are never registered.
It almost looks like the hub is in "permanently attached" mode. I have no way to check this because the SMB interface on the hub is not connected to the host so I can't read the internal registers.
The hub receives the 3.3V power directly from the host power supply system and the 1.1v power supply is derived from this.
The hub receives its reset input from the host reset system. All required timings are met per the data sheet. (System POR is about 160mS - TPS3823)
The VBUS input is also derived from the 3.3V supply so a different voltage divider is used to produce 500mV on this pin (56K and 10K).
Currently, I am only operating the hub in USB 2.0 mode (owing to a design error with the SSUSB interface on the upstream side)
What I would like to know, is there any way that the hub can be put into permanently attached mode other than by programming the relevant register?
Any suggestions? We can send schematics snippet if necessary.
Thanks,
Mark
