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TUSB2036 permanently attached device vs external port

Denis Alain1
Intellectual 600 points
Other Parts Discussed in Thread: TUSB2036

Hi,

What is the purpose of permanently attached devices option of the TUSB2036? We have 2 USB devices connected to this hub on our board. So basically speaking, they are permanently attached! But, we wired everything has they were externally attached to a USB port... Is-there any problem of connecting this that way?

From what I understand, except for *maybe* fastest enumeration, it shouldn't be important!
Thanks,
Denis 

  • 0
    TI__Mastermind 36085 points

    Hello Denis,

    Since the implementation point of view, You shouldn't have any issue regarding to the connection, however the devices and the ports should have configurated the option "permanently attached device" for power management, test and certification purposes.

    For instance, according to the USB Specification Revision 2.0, section 11.13: "A compound device may power both the hub electronics and the permanently attached devices from VBUS. The entire load may be reported in the hubs’configuration descriptor with the permanently attached devices each reporting self-powered, with zero MaxPowerin their respective configuration descriptors."

    Best Regards,

    Diego.

  • 0 in reply to Diego Cortes
    Intellectual 600 points

    Hi,

    Thanks for your reply! I think I need to review the USB specification.

    From what we experienced until now, everything is working fine with the TUSB HUB / devices, except that sometimes, one device is not waking-up from the suspend mode when the power is applied to the board (and the USB HUB is connected to the PC). I'm suspecting a specific USB device problem. Resetting this particular USB 2.0 device "correct" the problem... but this is a patch that I don't want to use in the field.

    If you have any clue for us (for the TUSB circuit), we will happy to take a look at it. Again, I'm not sure that the HUB is the problem itself.

    Regards,

    Denis

  • 0 in reply to Denis Alain1
    TI__Mastermind 36085 points

    Hello Denis,

       I am agree with You, It seems to be a device issue and my suggestion is to use another device for testing purposes (is highly recommended to use a certificated USB device).

    Regards,

    Diego.