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USB: Can I Add another device by soldering it inside?

Discussion in 'Electronic Basics' started by asdf, Nov 3, 2004.

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  1. asdf

    asdf Guest


    I hope someone would be able to help :) I want to add one smal device to my
    computer by soldering it to the inside of the USB connector. If I do so,
    would I stil be able to use this same connector from the outside, in the
    regular way?

    I have a small USB dongle (BLuetooth) that I would like to "install" into my
    notebook. When used as a dongle, Bluetooth is constant source of the
    problems: I must pair it often or I do not have it with me when I need it.

    I would therefore solder a small cable to the back of the USB port inside of
    my notebook and connect the dongle to that cable and just place such
    combination inside, where I have spare place.

    Can this be done and stil retain usage of such USB port from the outside or
    I could not connect any other devices on the outside while this "inside"
    Bluetooth dongle is active or I could never use external part of the


  2. Joel Kolstad

    Joel Kolstad Guest

    No. A USB connector can only connect to one device at a time; connecting to
    multiple devices requires significantly non-trivial electronics. If you
    open up a USB hub you'll see it contains an IC that performs this
    functionality. Although (for USB 1.x) the _signal lines_ are more or less
    just 'repeated' between all devices, a hub must be intelligent so that the
    host can tell it to 'power up' one device at a time for enumeration.
    Afterwards, the host polls the hub so that it can detect device removal,
    overcurrent conditions, etc.
    Why do you think that connecting it inside of your laptop is going to help
    this problem in any manner?
    You have a few options:

    1) Get the smallest hub you can find -- some are very tiny -- and install
    that as well inside the laptop. Be sure to get one that allows external
    power to be used, as otherwise the 'new' external connection will
    (typically) only tell the OS that 100mA of power is available.

    2) Connect the D+/D-, and Gnd lines to your dongle and use a SPDT switch to
    alternatively powerup the dongle's +5V line or the external connector's +5V
    line. This violates the USB spec and no one would guarantee you that it
    will work, but there's a decent change that it would.

    ---Joel Kolstad
  3. John

    John Guest

    Have you ever wondered why they sell USB hubs? USB can support a
    number of devices, but it's not a daisy-chain connection. If you wire
    the Bluetooth device, you lose the use of the port externally.

    On the practical side:

    1. Have you opened the notebook and found space for the dongle?

    2. Are you willing to give up some of the Bluetooth range if the
    dongle is buried inside the notebook?
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