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  1. #1
    Farab
    Guest

    USB bus powered devices

    I would like to connect an USB drive to the 7390, but it doesn't have a power supply of it's own, it is USB bus powered. Does the 7390 provide enough power on it's USB bus to support such devices?

  2. #2
    Ess Tee
    Guest

    Re: USB bus powered devices

    Hi Farab Welcome to the Fritz!Forum.

    The specification for the 7390 does not specifically say the USB Ports are Powered, so it has to be assumed that they are not.
    That said the Manual implies that ‘some’ power is available but recommends using a Powered Hub [See Manual extract below].

    I am very busy right now setting the F!F up, but we will ascertain the precise situation regarding this subject and confirm the outcome later.

    A workaround to the situation would be to use a Powered USB Hub.
    Ensure that the Hub will be capable of supporting your USB drive [?HDD].
    Also keep in mind the restriction of running a maximum of 4 USB Devices on the 7390.

    From the 7390 Manual Page 63:
    One or two USB hubs can be connected to the USB ports
    of the FRITZ!Box. A USB hub is a device to extend existing
    USB ports.
    If the printer cannot be selected, it may be possible
    to select a compatible printer or printer driver.
    If you use USB hubs, note that a maximum of four USB devices
    can be operated on the FRITZ!Box.
    We strongly recommend using USB hubs with their own
    power supply.

  3. #3
    toekneem
    Guest

    Re: USB bus powered devices

    Hi Farab,

    If you look at the hard drive ,check if the power requirement is less than 0.5A then yes it should work. The USB 2.0 specification states, the total current consumption may not exceed a value of 500 mA. Otherwise unspecified errors on the USB devices or even damage can occur.

    Much , much better to get a powered device

  4. #4
    Ess Tee
    Guest

    Re: USB bus powered devices

    Hi again Farab

    As toekneem says there are limits specified by USB Specifications.

    The official AVM response is:

    You may attach USB devices that follow the standards USB 2.0 and 1.1.

    The USB host will offer a maximum of 500mA.

    Only one single USB device with a power consumption of 500mA will be
    supported. Further USB devices attached to the FRITZ!Box must have a
    maximum of 100mA power consumption.

    Please find our information on supported USB devices here:


    FRITZ!Box 7390 - Type & number of USB devices that can be connected

    The situation is fairly complex and it would seem prudent to follow the above Link, to read and absorb the information there.
    We are seeking further clarification regarding the AVM statements:

    The USB host will offer a maximum of 500mA.

    and:

    Only one single USB device with a power consumption of 500mA will be
    supported. Further USB devices attached to the FRITZ!Box must have a
    maximum of 100mA power consumption.


    The above 2 statements are in conflict, if there is a Maximum of 500mA installing 1 USB device of 500mA exhausts the supply capability and ‘further’ devices would seemingly cause an overload?

    This situation seems to be further restricted by an important statement in the Link, where it says:

    Important:
    The FRITZ!Box can only supply one USB device at a time with power.
    When connecting more than one USB device without its own power supply, an active USB hub (with its own power supply) will be required.


    Personally I stand by the recommendation to use Self Powered USB Hubs and keep to the limitations defined.

 

 

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