Splicing power into host line of un-powered hub

I have a 5v 2amp adapter and a un-powered usb hub. The adapter
supplies power to the beagleboard through the barrel connector. Can I
wire the usb host cord to the power supply in parallel to drive high
power usb devices like HDDs?

Can you draw a diagram as to what you are wanting to do? It is unclear to me where the power is connecting to.

Gerald

A lot of unpowered USB hubs have a power connector, even if they don't
come with an adapter. This is true of the one I use with my
BeagleBoard B4. I have two cables coming out of my 5V supply, one to
power the BeagleBoard's barrel connector and a second one to power the
USB hub. In the USA, you can find many power connectors at Radio
Shack, otherwise Digi-Key has pretty much everything.

I'd be leery of messing with power on the BeagleBoard itself. Check
the schematic for your version BeagleBoard very carefully and be sure
to indicate which version you have when asking for advice from the
group. The USB standard is designed to have hubs automatically output
more or less current depending on what the device asks for. I imagine
high-end hubs implement this faithfully. Cheap hubs like mine just
connect all the +5V lines together, with a few diodes. I don't know
what the BeagleBoard hardware and software do.

My warranty-free advice is to see if you can splice a power cable for
the hub into your existing 5V supply's cable and leave the BeagleBoard
unmodified. You're much better off accidentally destroying a $10 hub
or power supply than a $150 BeagleBoard.

Hope this helps.

Here’s a diagram indicating the connection that I want to make:
http://img217.imageshack.us/i/powersplice.png/
Let me know if anything is unclear.

“Cheap hubs like mine just
connect all the +5V lines together, with a few diodes. I don’t know
what the BeagleBoard hardware and software do.”

Well, my hub is definitely cheap!
99cents from china rotflmao

I done similar for one of my robot in order to directly power a USB
camera requiring additional current.

Leave the +5 on the Beagle USB disconnected. Tie the 3 ground wires
need to be connected together. And of course the data lines between
the Beagle USB and the HUB.

Regards.
- James Ronald

BTW, verify that the hub works before you start hacking. I have had
poor results with my C2 when using cheap china USB powered hubs.
However, my $29.00 Belkin USB hub works perfectly.

- James Ronald

“Leave the +5 on the Beagle USB disconnected. Tie the 3 ground wires
need to be connected together. And of course the data lines between
the Beagle USB and the HUB.”

What an elegant solution. That will insure no damage to the board. I am confused though. For power, there are only 2 wires, + and - (red/black). Will omitting the 3rd connection from my power supply leave any lack of function? I see no wire for it.

“BTW, verify that the hub works before you start hacking. I have had
poor results with my C2 when using cheap china USB powered hubs.
However, my $29.00 Belkin USB hub works perfectly.”

The hub works. It is actually very nice. A “squid” style that I am rather fond of.

In the past I too have had trouble with a cheap powered hub. The trouble was not so much with the hub itself but with the power supply. It fluctuated so tempestuously that my board would not even power up. I am lucky that no (perceived) damage was done.

There four wires for USB. All 3 (USB on the beagle, power adapter and USB HUB) of the grounds (black) need to be connected. The two data lines (you may not have cut them, I usually end up doing so) and only connect the 5 volts from the power adapter to the hub. When connecting a USB device, it is correct to NOT connect the power (5 volts) to the USB port on the beagle.

  • James

Okay. Thank you for clarifying. Just to be certain, the positive lead from my power supply goes to red and the negative goes to black, correct?

Another diagram to avoid confusion =)
http://imageshack.us/photo/my-images/718/powersplice2.png/

Yes, your diagram is correct.

- James Ronald