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Thread: XMC4500 Which signals observes USB module to detect a connection

  1. #1
    Intermediate Intermediate Ing99 is on a distinguished road
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    XMC4500 Which signals observes USB module to detect a connection

    Hi Infineon,

    at xmc4500/4800 please which signals observes the usb module to detect a new connection when used as B-device? Only DP and DM or VBUS too? We need isolation via ADuM3160 (Analog Devices) and the chip transfers only DP and DM. Thanks for the answer.

    Best Regards
    Wolfgang

  2. #2
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    MichaelIFX is on a distinguished road
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    For a self-powered device you generally need to monitor VBUS signals to control the pull-ups.
    See also USB Specification
    http://sdphca.ucsd.edu/Lab_Equip_Manuals/usb_20.pdf
    "The voltage source on the pull-up resistor must be derived from or controlled by the power supplied on the USB cable such that when VBUS is removed, the pull-up resistor does not supply current on the data line to which it
    is attached."

    How this is exactly achieved with ADuM3160 I'm not sure.
    The views expressed here are my personal opinions, have not been reviewed or authorized by Infineon and do not necessarily represent the views of Infineon.

  3. #3
    Intermediate Intermediate Ing99 is on a distinguished road
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    Hi Michael,

    thanks, I hope I have it now.

    The pullups/downs are used to signal the speed capability to the host (master). The ADuM3160 does this by the setting of the SPU pin. Tied to VDD1 signals high-speed to the host.
    On the XMC side the same (pin SPD).
    When the XMC is used in device mode, the device connect process varies depending if the VBUS is on or off when the device is connected to the USB cable (see Ref.Manual V1.6 page 16-73).

    My test result: The usb bus is running fine when feeding the VBUS signal from the cable only to the ADuM3160 (feeds the cable side) and the VBUS pin of the XMC is connected to 3.3V. The only information transferred from the cable to the XMC are now DP and DM.

    Best Regards
    Wolfgang

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