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R-Pi USB Connections
http://www.x404.co.uk/forum/viewtopic.php?f=4&t=16709		 Page 1 of 1
Author:  paulzolo [ Fri Jun 22, 2012 12:32 pm ]
Post subject:  R-Pi USB Connections
OK - I’m posting here as it’s aPC and it’s hardware related. It’s certainly not a Mac. :lol:

My question is about USB. Right now, to power up (and down) the Pi, I need to pull the USB plug from the Pi and re-insert it. This has a finite life, and I’d rather not have to do this all the time. I am, as some may well have guess, been tinkering with early RISC OS Alpha builds, and this requires a lot of power cycles.

I am also pondering building a box for it, and this would need access to the ports, as well as providing power to the system. The best option I can think of is using a USB hub to power the Pi, and ALSO to provide a way to extend the USB capabilities of the Pi.

So, my question is: is it safe to do this? Basically, the USB hub would be connected to the mains. The data in cable would be connected to the Pi. One of the “out” ports would be connected to the Pi’s power in socket. See this diagram:
ImageClick for large view - Uploaded with Skitch

Is this kind of loop-back OK to do? I’m posting this on the Raspberry Pi forums as well, but I’m after opinions. I’d rather have one power lead (USB hub) than two (hub+Pi).
Author:  John_Vella [ Fri Jun 22, 2012 1:43 pm ]
Post subject:  Re: R-Pi USB Connections
What I'm planning on doing with my Raspeberry Pi, when it finally arrives, is putting it in an oversized case with case mounted connectors from the board. Theres no reason why you couldn't splice a switch into the usb power cable, but I wouldn't even bother with the system you've described... it simply looks too complicated to bother with.

When I get home I'll mock up an image showing how mine will be wired up, but for now what are you planning on using your Pi for?
Author:  paulzolo [ Fri Jun 22, 2012 2:00 pm ]
Post subject:  Re: R-Pi USB Connections
John_Vella wrote:
What I'm planning on doing with my Raspeberry Pi, when it finally arrives, is putting it in an oversized case with case mounted connectors from the board. Theres no reason why you couldn't splice a switch into the usb power cable, but I wouldn't even bother with the system you've described... it simply looks too complicated to bother with.

When I get home I'll mock up an image showing how mine will be wired up, but for now what are you planning on using your Pi for?


Right now, I’m goofing about with RISC OS - which is in serious pre-Alpha territory. That will likely change as I start trying other things with it. I’ve also got a Debian install on it - but so far, the wave of Acorn nostalgia is quite large :-)
Author:  pcernie [ Fri Jun 22, 2012 4:50 pm ]
Post subject:  Re: R-Pi USB Connections
First of all, I'm on the vodka and haven't even read everything here ;) , but would a USB wall plug work? Or is that too much juice to risk or whatever?
Author:  paulzolo [ Fri Jun 22, 2012 7:25 pm ]
Post subject:  R-Pi USB Connections
pcernie wrote:
First of all, I'm on the vodka and haven't even read everything here ;) , but would a USB wall plug work? Or is that too much juice to risk or whatever?


It should do - though the Pi requires 700amps and USB generally delivers 500. That aside, I am getting on OK with my iPad charger. However, the way you power the thing up and down is to yank the plug from the board. It's just a potential weak point. If you want to put more devices on your USB chain, you'll need to power the Pi and the USB Hub. Infact, the people on the Raspberry Pi forums say that my diagram is correct, and I can run it like that. They do advise on using a Y to put 2 sockets worth of power into the power on the Pi to cover its needs.

That said, a simpler option has been mentioned here, so I'll see what can be suggested.
Author:  big_D [ Sat Jun 23, 2012 7:03 am ]
Post subject:  Re: R-Pi USB Connections
If you are handy with a soldering iron and cable cutters, you could put a power switch in series on the "power" cable running into the Pi.
Author:  soddit112 [ Sat Jun 23, 2012 11:46 am ]
Post subject:  Re: R-Pi USB Connections
I'm pretty sure Ive heard somewhere that the Pi can be powered through it's GPIO pins. if so, it might be as simple as adding a toggle switch to a pair of those, and then soldering the other ends to a spare USB plug, which could then be plugged into the hub as you planned. dont quote me on this though: i am not particularly good with electrics, and I can't find anything except the wikipedia page citing this :?

Currently im powering my Pi through my PC's front USB ports. my motherboard (MSI P67A-GD53) has a setting that allows it to pump up to 2A through them without device negotiation, so the Pi gets plenty of power :)

EDIT: found better information on the matter of powering via GPIO: http://www.elinux.org/RPi_Hardware#Power

Quote:
As the 5V rail is brought out in the GPIO pins, you can power the Rpi from there too. You should mind however, that those are behind the power protection circuitry, so you should provide your own.


sounds like it might be a little more complex than just adding a switch. still, if you know what you are doing it might be an alternative :)
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