chde
Posts: 16
Joined: Tue May 08, 2012 8:17 am

Re: USB Hub Issues

Thu May 10, 2012 9:57 am

I"ve just bought myself a Pi and have never found the need with a home computer to need a USB hub. Obviously with only two ports and no PS/2 connection, this is different with the Pi.

On the FAQ, the site says that the Pi"s USB functions can be expanded with "a USB hub". So, I went and bought myself a cheap USB hub, unpowered, which I thought would be sufficient. However, subsequent online searches and looking through the forums have revealed that I"d need a POWERED USB hub. And now I"m stuck with an unpowered one and am a bit strapped for cash.

I don"t want to damage my Pi, but after a bit of Googling, decided to ask your opinions. I only want to connect 4 devices at any one time - a mouse, keyboard, bluetooth dongle and WiFi adapter. Would an unpowered hub be sufficient for these, or would it cause errors and damage to the Pi?

Thanks for reading

Techmeology
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Re: USB Hub Issues

Thu May 10, 2012 10:16 am

I think you're unlikely to cause permanent damage to your Pi that way, however if you try to draw too much power, you may find that it becomes unreliable until you unplug stuff:

-Ethernet port may stop working correctly
-USB may stop working correctly
-The Pi may just switch off

These issues are caused by these devices having insufficient power, and are nothing to get immediately worried about (unplugging enough devices from the USB ports will fix it). That said, I'm not sure if it's impossible or not to damage the Pi by seriously overloading it with lots of USB devices and PSU capable of supplying a high current.
Check out cool stuff I'm doing, e.g my PIC Programmer for the Raspberry Pi: http://www.techmeology.co.uk/rpipic/

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RaTTuS
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Re: USB Hub Issues

Thu May 10, 2012 11:21 am

you will not be able to run all those from a unpowered hub

you wont do any harm to your Pi but it wont work
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jbeale
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Re: USB Hub Issues

Thu May 10, 2012 3:24 pm

The Pi was designed to provide only 100 mA current to each of it's USB ports (although the actual limit is more like 140 mA). Your desktop or laptop generally provides 500 mA, that is 5x as much. Many USB WiFi adaptors are in the 150 to 250 mA category and many/most of them do not work without a powered hub.

chde
Posts: 16
Joined: Tue May 08, 2012 8:17 am

Re: USB Hub Issues

Thu May 10, 2012 3:52 pm

Oh, if they take up that much, would a USB WiFi adapter function at all on the Pi, plugged straight in, without a hub?

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RaTTuS
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Re: USB Hub Issues

Thu May 10, 2012 4:22 pm

chde said:


Oh, if they take up that much, would a USB WiFi adapter function at all on the Pi, plugged straight in, without a hub?


I've not had any luck so far but I've not tried in anger
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