USB port selector hub (not a regular hub)

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MrAl
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USB port selector hub (not a regular hub)

Post by MrAl »

Hi there,

I ended up with a nice 10 port USB hub that is defunct due to a wrong adapter being used, so i was
thinking of making a new hub out of it with some switches. The idea is that the switches will
switch in or out a SINGLE device (such as a USB memory stick) one at a time, so that there will
only be ONE device connected at any given time, yet they wont have to be unplugged and plugged
back in.
The only drawback is that it looks like it will take 3 pole switches to do this, to switch on/off the
two data lines plus the 5v power line for each connector port.

Anyone ever try this ?
LEDs vs Bulbs, LEDs are winning.
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sofaspud
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Re: USB port selector hub (not a regular hub)

Post by sofaspud »

In giving it some thought I think I would look into using a CD4066 CMOS switch for each port. I envision a microcontroller
then being used to enable/disable each port, with a user interface of ten pushbuttons and (optional) 10 status LEDs.
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haklesup
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Re: USB port selector hub (not a regular hub)

Post by haklesup »

I'd take a close look at Maxim's line of analog switches and muxes. They have a variety of switch configurations and ones specifically built for USB. Sampling from Maxim is generally pretty generous too.

Let us know if you're having trouble selecting one and I'll take a closer look and maybe recommend a few.

I think one switch per channel and some combinational logic for the enable lines should do it.
SETEC_Astronomy
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Re: USB port selector hub (not a regular hub)

Post by SETEC_Astronomy »

Make sure whatever method you choose powers the devices before connecting the data lines. If you'll notice the power pins on a USB connector are longer so they make first and break last.
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MrAl
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Re: USB port selector hub (not a regular hub)

Post by MrAl »

Hi again,


sofaspud:
Well, i dont think the 4066 or related is fast enough is it?
It would have to pass 480bps for the USB 2.0 spec. That might
require a bandwidth of 1.5GHz min or something like that.

hakle:
They have extremely high speed switches? Sounds interesting.
Have a part number handy?

SETEC:
Yes, i noticed that too but havent yet given it much thought.
You think it would matter that much? Many devices are made with
a tiny boot up delay, but i dont know about things like USB
thumb drives if they do or not. The device plug has different
length pins while the hub port does not, but that's enough to
make me think about this for a while.
What do you think the effect of having the data lines become
connected a tiny fraction of a second before the power would be?
LEDs vs Bulbs, LEDs are winning.
SETEC_Astronomy
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Re: USB port selector hub (not a regular hub)

Post by SETEC_Astronomy »

After more thought I think you'll be ok. What part(s) of the hub will you be salvaging? The connectors, case, etc.?
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MrAl
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Re: USB port selector hub (not a regular hub)

Post by MrAl »

Hello again,


The only parts of the old hub that are bad are the USB chips inside, and there is not much to it
anyway, just some connectors and some blue LEDs (one for each connector).
There's also the input connector which is USB type B, and a power connector which is the
type that accepts a wall wart plug probably 5.5mm diameter.
The things that will not be used are the two chips as they are blown out anyway, and the
power connector because it will not need separate power.
The things that will be used is maybe 5 out of the 10 connectors (i dont need 10 ports).
and the associated blue LEDs. The blue LEDs will be turned on when that connector is
selected ie it's power line is turned on. The housing will also be used, but will probably have
to be extended a bit to accommodate the extra size of the switches. I have not figured
out exactly how this is going to be done yet because i dont have the switches yet so i
dont know the size or anything like how they mount.

What inspired this project was partly something i was thinking of doing before this, and also
that now i have a nice hub that is blown out so it's not good for anything else anyway,
but also that i realized a while back that if something goes haywire with the USB power line
(+5v) it could blow out EVERY single USB stick plugged into it, and if that contains your
backup data your beat :sad: Also, now i have actually seen that happen with the friends
computer where there were quite a few USB sticks lost because of that, and once they blow
out they take the mem chip with it so you cant recover your data (and some of them only
contain one single ic chip anyway and it blows out due to over voltage).
LEDs vs Bulbs, LEDs are winning.
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MrAl
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Re: USB port selector hub (not a regular hub)

Post by MrAl »

Hi again,


Took a look at Maxim's chips for USB switching. The do look interesting, but i'll probably go with
regular switches because it will be a bit easier than working with their tiny QF packages, and
also this way there is no way two USB sticks (for example) can get hooked to the same USB
port if something goes wrong (except a short of course).
I found a way to wire up the switches so that no two USB devices can be plugged in at the
same time. It's not difficult really.
LEDs vs Bulbs, LEDs are winning.
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