unable to enumerate USB device

[Jim]

Mikkel L. Ellertson wrote:
> Jim wrote:
>   
>> To get a hub to work with all devices, hubs must have their own power
>> source externally.
>> Hubs that get there power source from the computer are the ones that
>> give you problems, because of voltage drop across the cable to computer.
>>
>>     
> Considering the amount of current we are talking about, I do not
> think voltage drop is a problem. On the other hand, with a bus
> powered hub, all the devices, plus the hub itself, are limited to
> the max current of the port you are plugged into. A limit of
> 500ma/port is common, but it could be less.
>
> Voltage drop = current x resistance
> .5v = 500ma x 1 ohms.
>
> Mikkel
>   
I have had a number of bad experiences with bus powered hub, devices 
that would not work in hub I plugged directly to
computer and they work fine, so i purchased external powered hubs and 
have had no more problems
As far as the voltage drop goes it depends a lot on how the USB device 
was designed as to how much current it's going to draw. I'm quite 
familiar with OHMS Law.

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IxR