USB hub questions

[zippity]

Hi everyone,

I've registered my interest with Farnell and RS and while I'm waiting for them to give the green light for ordering, I've been looking at some accessories for the Pi.

I have a ton of ideas for the Pi, but some of them are going to require some extra storage space and bigger SD cards don't seem to be very good value for money compared to a harddrive.

I've been reading the forums and from what I've seen so far, it would seem that I'm most definetely going to have to buy a powered USB hub to get enough juice for an external hard drive, which would add roughly another €15 to the total price, looking at what some computer shops in the area are offering.

I'm kind of a hardware noob though, so could anyone tell me if there are any specific requirements the hub should have in order to work with the Pi? And would it be possible to power the Pi itself off a powered USB hub that's also being used for a hard drive, keyboard, mouse and maybe a wifi dongle?

[crashmk92]

I purchased the Dlink H4 4 port hub.  I intend to use it as both a hub and power supply.  The hub itself is "sefl powered", as it utilizes a power supply of its own to support things such as hard disks, etc...

My intent is to power the PI off of the the hub, and then loop "back" into the hub from the pi for the bus data, leaving me with 4 ports remaining (1 on the pi, 3 on the hub).

Hope this helps.

Joe

[domesday]

Powering the Raspberry Pi of of the hub would in theory be possible but some hubs will stick rigidly to the spec of making 500mA available on a port and the Raspberry Pi needs 700mA. In that respect a cheap no name hub will probably be better as it is likely to ignore the standard and just connect the power lines directly to each port without any power restriction.

Nothing special is needed for the hub all modern hubs generally work without requiring drivers so will just work with any linux you have on the Raspberry Pi.

[TheCrazyInventor]

It's kind of "nasty" to power an entire harddisk purely through USB, because you'll be exceeding the official USB power specs. The Pi can probably handle all that just fine, but it's still nasty. A better solution would be to use an external power source for your harddisk. I don't know what type of disk you want to hook up, but I would probably go for a standard 3.5" hard disk with external power supply.

[zippity]

Right now I have a spare 160 GB pocket size/portable harddrive laying around that receives its power from the USB port. That's probably what I'll be using initially. I'm guessing the USB hub should be able to power it.

[wifiuk]

i got this from ebay

http://www.ebay.co.uk/itm/2509.....1423.l2649

£3.48

[nugget]

I like the bit where it says "TOP QULITY"!

Do you know what the specified power output is? Maybe it'll be fine, I guess at that price it's worth a punt.

[glenn66]

I've successfully connected an 80GB external drive (with a dual USB cable) to the USB port on an Android tablet by connecting the 'signal' USB plug to the tablet and the second 'power' plug to a small 1 amp (1000mA) USB power supply.  The HDD required 650mA, but the tablet port could only supply 250mA, not the 500mA that the USB specification states.  This is not uncommon for battery-powered devices and the RaspberryPi will most likely be the same.

With a powered hub you need to check the power supply.  The ones I've seen were around the 1000mA mark so over 5, 6 or 7 ports each port will not be able to supply anywhere near the full 500mA and you might only be able to use 2 or 3 before the external HDD would stop operating.

That hub looks the business Wifiuk, thanks for posting the link, I might buy myself one.

[Phil Spiegel]

To keep to the idea of portability which  the small size AND small power consumption of the Pi -although it may seem a higher initial cost, the ideas of using either SD or USB-memory sticks as local storage would seem the best recommendation to me.

And making use of the Network connections for higher capacity storage for other than immediate needs - or even, as some have suggested .. a wireless network connection back to your less-mobile storage system.

For me, thewhole point of the Pi is its compact overall size -even with Gertboard- so that I can 'embed' them in each of my model railway boards to provide various aspects of control - without lugging great boxes of electronics around !

(As an aside: I have a miniature 'PC-case' AM radio (case, keyboard ,mouse and 'CRT monitor' approx 100mm x 100mm x 100mm into which I'm thinking of putting a Pi as a 'slightly overscale' PC on the layout.. fitting a 4" lcd screen into the 'monitor' (loudspeaker))