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TUSB4020BI: removable device fail

Part Number: TUSB4020BI

Hi, it'Andrea Orazzini from CAEN SpA (Viareggio, Italy). I have designed an hub USB using the TUSB4020BI. I need to connect to the hub a mouse and a keyboard. However it seems that the hub works only if the boad is powerd with at least one device attached. If I power the boad with no device connected or if I disconnect both devices during the operation, I can't reconnect the mouse and the keybord.

I have tried in two configuration mode:

1) PIN 32 SMBUSz not connected and no I2C communication;

2) PIN 32 SMBUSz tied to GND with 4.7K Ohm resistor. In this case I send via I2C 0x83h  to the configuration register (7h) and then clear the cfgActive bit of the Device Status an Command Register (F8h).

In both case I have the same results. If I have no device connected to the hub, I can't connect anything.

Can you give me some suggestion?

Kind regards,

Andrea Orazzini