Q: How does USB hubs work? Re: Multiple USB Devices

Robert Michel openmoko at robertmichel.de
Wed Jan 31 13:12:53 CET 2007


On Wed, 31 Jan 2007, Michael Fletcher wrote:

> >> I was wondering, I have been searched the mailing list, but can't seem 
> >> to find an answer.  Will it be possible to connect a powered USB HUB 
> >> into the 1973.  So that for example the phone can charge, have a USB 
> >> WiFi dongle attached and a USB mouse/keyboard all connected at the same
> time?
> >yes.
> Brilliant! Thanks for that :-)

So now the question, how does an USB hub work?
Can we plug in the host on any port?

The Neo1973 will have mini-USB-B

normal hubs powered USB-A for the adapter 
and one unpowerd USB-B for the host.

So to connect the Neo with a PC we have a mini-USB-B to USB-A cable. 
1.) Can we plug the Neo with USB-A it into the (battery powered) hub
    and charge it whith it?  (I think yes)
2.) Can we plug the Neo with USB-A it into the (battery powered) hub
    and use an USB device plugged into the hub?

So reducing the USB connector and adapter mess...
we could modifiy a (battery powered) hub in a way that on USB-A port
will be an unpowered one (or just switchable power). Then could
we deccide if we want to charge the Neo with the hub or not.
(And we don't need a mini-USB-B to USB-B cable/adapeter)

So how behave USB hubs? Just stupied forwarding to every port,
no special host port (internaly)?


PS: And what would happen when two hosts are connected to one hub?

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