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abishur
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Re: Can a powered hub feed R-PI?

Mon Oct 31, 2011 1:30 am

Actually I was talking about using the $35 dollar pi from the get go, no sense buying the model a and then have to pay for an ethernet adapter as well ;) I don\'t know that the $5-$10 max is accurate, it was a rough guess on my part based on what I\'m estimating would be the total cost of the chip, additional ports, and cost of additional layer spread out over the cost of the entire batch. :?

I\'ve been thinking more and more about the original issue. Could you power the device via the USB hub. I still like Obart\'s idea of splitting the line coming off the PSU and taking it to both the hub and the r-pi, but I want this to be transparent because that\'s cooler :P

So here\'s my thought. Crack open that USB hub and solder a jumper cable from the +5 and ground pins on the USB power jack. On the uplink port, cut the power pins of the USB port and attach them to the jumper wires.

Then over on the r-pi cut the power pins on one of the ports to they\'re not attached to the PCB. Take two more jumper cables and solder them from the power pins (which is technically receiving power straight from the PSU at this point) and attach the other end to the micro USB form factor power supply power pins.

The data still transfers over the affected port allowing the uplink to function properly, but take the power straight to the micro usb power jack. The USB devices shouldn\'t care as they\'re all receiving power from the USB hub anyway.

And externally one wire is traveling from the hub to the r-pi keeping things neat and clean.
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Re: Can a powered hub feed R-PI?

Mon Oct 31, 2011 2:10 am

[quote]I\'ve been thinking more and more about the original issue. Could you power the device via the USB hub. I still like Obart\'s idea of splitting the line coming off the PSU and taking it to both the hub and the r-pi, but I want this to be transparent because that\'s cooler :P

So here\'s my thought. Crack open that USB hub and solder a jumper cable from the +5 and ground pins on the USB power jack. On the uplink port, cut the power pins of the USB port and attach them to the jumper wires.

Then over on the r-pi cut the power pins on one of the ports to they\'re not attached to the PCB. Take two more jumper cables and solder them from the power pins (which is technically receiving power straight from the PSU at this point) and attach the other end to the micro USB form factor power supply power pins.

The data still transfers over the affected port allowing the uplink to function properly, but take the power straight to the micro usb power jack. The USB devices shouldn\'t care as they\'re all receiving power from the USB hub anyway.

And externally one wire is traveling from the hub to the r-pi keeping things neat and clean.[/quote]This sounds right. I\'m not sure how easy it is to do in reality, but from a technical point of view it\'s correct. I suspect the USB connector are molded into plastics (at least the few I\'ve handled) so cutting and soldering isn\'t obvious solutions. But it might be possible to find a hub with open connectors.

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Re: Can a powered hub feed R-PI?

Mon Oct 31, 2011 2:30 am

Yeah, it would take a very fine hand to snip/cut the right pin then gently bend it outward so you could easily solder it. :(
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Re: Can a powered hub feed R-PI?

Mon Oct 31, 2011 3:04 am

@abishur the LAN95xx chips are identical except for 6 pins. Four Data (bottom of chip left of center for data pins) and two positive power pins (Right side lower pins). The negative (commons) are too the board, as far as I know. All of the other pins appear to be the same. I do not have the equipment, the eyesight or the steady hand it would take to replace the LAN9512 with a LAN9514 chip. If you could do this then you could carry out the other two USB as dongles. This is kind of a moot point as the RasPi will, in the current design, not be able to power these extra ports at all.

@hippy that drawing is pretty close except for there will be no break in the line. There will be a micro USB connector to the RasPi. I actually have a power supply that can deliver 12v and 5v (musicPower by Powerline). It only puts out 2.5 watts to 5v and 6 watts to 12v. This would run the RasPi and the router but not the powered hub. Since I need (well want) a USB HDD I am stuck with using a powered hub now. I could have made the setup work without the powered hub on the previous power design. I am looking for a diagram and parts list of a switching regulator to build or buy.

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Re: Can a powered hub feed R-PI?

Mon Oct 31, 2011 3:17 am

@abishur that will definitely work. It is going to depend on the hub as to how you get the inside of the connector. It might be possible to cut the trace to the port then solder directly to the pins that stick through most of these boards. Most of the ones I have seen, opened up, are through-hole design. This is the method that I used for the Router I modified, except I did not bother to cut the traces. I just plugged a RJ45 into the port so it would not be used twice. There was no power to worry about at the hub. Definitely a good chance to ruin the hub so buy an inexpensive powered hub to try this with.

@kme the USB ports inside a hub do not (usually) have a plastic covering over them, sometimes shrink tube, which is easy to remove.
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Re: Can a powered hub feed R-PI?

Mon Oct 31, 2011 3:34 am

[quote] If you could do this then you could carry out the other two USB as dongles. This is kind of a moot point as the RasPi will, in the current design, not be able to power these extra ports at all.[/quote]Could you please elaborate? Why couldn\'t a fictional 9514 board be powered? All the ports are non-powered so they can only draw marginal power. That can\'t possibly burn out the +5 V USB lines on the PCB.

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Re: Can a powered hub feed R-PI?

Mon Oct 31, 2011 4:07 am

@lobo, I think you\'ve misunderstood my idea (should have done a photo!) I\'m not talking about unsoldering or even touching the LAN9512 at all! I\'m talking about cutting the power pins on the USB ports itself where they are soldered onto the PCB and attach jumper wires from the cut pins to the power pins on the usb micro power jack.
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Re: Can a powered hub feed R-PI?

Mon Oct 31, 2011 4:43 am

@ abishur So you want to steal the power coming \"in\" from the hub from one of the onboard USB ports, and jump it to the micro USB power port?. The connection port from any hub is not powered. The power goes out of the (RasPi) host port not in from the hub. Yeah I would need to see what you have in mind.

@kme your just another brick in the wall. \"Hey Teacher, Leave those Kids ALONE\". You are right you would get marginal power. You would double the ports and cut the power to those ports about in half if I am guessing right. The power is limited on the RasPi side not the LAN9512 or LAN9514. They each can handle (regulate) up to 500ma per port. The RasPi does not appear to now be able to deliver that to the LAN9512.
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Re: Can a powered hub feed R-PI?

Mon Oct 31, 2011 5:22 am

@lobo, I think you need to go back a page and read my second post, I actually explain it rather decently and that\'s not at all what I\'m suggesting :P
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Re: Can a powered hub feed R-PI?

Mon Oct 31, 2011 5:58 am

[quote]The power is limited on the RasPi side not the LAN9512 or LAN9514. They each can handle (regulate) up to 500ma per port. The RasPi does not appear to now be able to deliver that to the LAN9512.[/quote]You have to spell that out for me. As long as the PSU can deliver the juice and the R-PI doesn\'t exactly melt down I fail to see the problem. And with a reasonably assumption two ports will be keyboard and mouse only those won\'t even come close to 500 mA per port at any time.

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Re: Can a powered hub feed R-PI?

Mon Oct 31, 2011 12:41 pm

[quote]Quote from kme on October 31, 2011, 05:58
[quote]The power is limited on the RasPi side not the LAN9512 or LAN9514. They each can handle (regulate) up to 500ma per port. The RasPi does not appear to now be able to deliver that to the LAN9512.[/quote]

You have to spell that out for me. As long as the PSU can deliver the juice and the R-PI doesn\'t exactly melt down I fail to see the problem. And with a reasonably assumption two ports will be keyboard and mouse only those won\'t even come close to 500 mA per port at any time.[/quote]

I think what lobo is talking about here is the reason why the USB ports can only give 100 mA. The way the power is working right now you have the +5V coming into the usb micro power jack, where is goes through over voltage and over current protection. It then splits with 5V going to the GPU (Where a built in regulator steps it down to 3v3... and 1v2 I think) and 5v going directly to the usb hub. The hold up, from what I understand, is the over current protection that comes in the form of the self resetting fuse. It limits the draw of the USB ports to the basic 100 mA. I\'m sure there\'s a piece of the puzzle I\'m missing that let\'s the r-pi to know to regulate the power to the ports, but I\'m not sure where that is ;)
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Re: Can a powered hub feed R-PI?

Mon Oct 31, 2011 1:41 pm

[quote]Quote from abishur on October 31, 2011, 12:41
The hold up, from what I understand, is the over current protection that comes in the form of the self resetting fuse. It limits the draw of the USB ports to the basic 100 mA.[/quote]

That was my impression also.

If that is the case then a simple option would be to drop a blob of solder on the fuse and remove current limiting altogether. You\'d then only be limited by what the PSU can deliver and currents which would burn the PCB tracks off the board :-)

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Re: Can a powered hub feed R-PI?

Mon Oct 31, 2011 2:41 pm

Or desolder the fuse off and put a higher amperage one in it\'s place.
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Re: Can a powered hub feed R-PI?

Tue Nov 01, 2011 2:07 am

Okay so it turns out we had misunderstood something. It\'s been made clear from an official source that the only limiting factor on how much the USB ports will be able to draw is the self resetting fuse. Right now, there\'s no official word on what that fuse will limit us to, but in theory the usb ports will be able to supply up to the fuse limit minus the power required to drive the r-pi itself.
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Re: Can a powered hub feed R-PI?

Tue Nov 01, 2011 4:51 am

@hippy I should have known you would come up with a solve like that ans it will work. There is also another limit which is how much current can a Micro USB connector handle?

@abishur I did go back and read the post, you plan on sending power down the uplink port which is usually unpowered. You do that by jumping from the hubs power input to the unconnected power pins of the uplink port. Hopefully these pins are still there to use, I have not checked an uplink port to see if they are. Then cutting the power ties or traces (port will not send power) to one of the two onboard ports (B model) then jumping to the actual power input port of the RasPi. Yes it will work to provide hidden power to the RasPi. Just be real careful that there are no shorts and that the power from the host port has actually been completely cut. Feeding power to an already powered port may create some magic blue smoke!
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Re: Can a powered hub feed R-PI?

Tue Nov 01, 2011 8:10 pm

[quote]Quote from hippy on October 30, 2011, 14:19
Because the R-Pi cannot be powered through its outgoing (host) USB ports, only the micro-USB power input ...
[/quote]

I\'ve just had a D\'Oh! realisation. If the 5V from the micro-USB power input feeds the USB ports directly ( via a fuse or not ) then the R-Pi can take power in through its host USB ports. That makes things quite simple ...

[img]http://www.raspberrypi.org/wp-content/u ... UBTHRU.gif[/img]

The splitter at the powered hub can even be made internal to the hub, allowing four devices on the hub ( increase the PSU up to 2800 mA @ 5V ).

Someone is probably going to say they suggested that, in this thread or another, and they are right; apologies for not seeing the light earlier.

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Re: Can a powered hub feed R-PI?

Tue Nov 01, 2011 9:37 pm

@abishur suggested it. Go back and see his post.
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Re: Can a powered hub feed R-PI?

Tue Nov 01, 2011 9:38 pm

...

I swear there\'s something they\'re not tell us here. Surely it can\'t be that simple :P
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Re: Can a powered hub feed R-PI?

Tue Nov 01, 2011 9:55 pm

Sorry for being a spoilsport, but sending power in through the downstream ports will render the protection circuits ineffective (no polarity protection, no overvoltage protection, no overcurrent protection), much the same as replacing the fuse with a much stronger one would. No risk, no fun, I guess.

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Re: Can a powered hub feed R-PI?

Wed Nov 02, 2011 1:16 am

[quote]Quote from Johannes on November 1, 2011, 21:55
Sorry for being a spoilsport, but sending power in through the downstream ports will render the protection circuits ineffective (no polarity protection, no overvoltage protection, no overcurrent protection) ...
[/quote]

If the Vin comes through micro-USB and via the fuse to the downstream USB ports and the rest of the R-Pi circuitry, and the over-voltage and reverse voltage protection is on the R-Pi circuitry side of the fuse, both over-voltage and reverse protection will still be effective when Vin comes in through one of the USB ports. Yes, the over current protection will have gone; simply add a fuse before the feed into the USB port.

The reverse voltage protection - presumed to be a crowbar diode or similar - has to be fitted on the circuit side of the fuse rather than the micro-USB side or it won\'t blow the fuse when wrong polarity is applied, it would just create a short across the USB PSU.

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Re: Can a powered hub feed R-PI?

Wed Nov 02, 2011 7:44 am

[quote]Quote from hippy on November 2, 2011, 01:16
The reverse voltage protection - presumed to be a crowbar diode or similar - has to be fitted on the circuit side of the fuse rather than the micro-USB side or it won\'t blow the fuse when wrong polarity is applied, it would just create a short across the USB PSU.
[/quote]

Exactly. Then it is a battle between the diode, the circuit traces and the power supply. If you\'re lucky, the PSU has its own polyfuse. If not, or if that fuse is too big for the reverse polarity diode or the voltage clamp, then the protection circuits will either become high-resistance and allow the overvoltage or reverse polarity into the Raspberry Pi or they will short out and need replacement before you can use the Raspberry Pi again. I would consider neither outcome \"successful protection\". (Note that the PSU might be a battery capable of delivering silly currents.)

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Re: Can a powered hub feed R-PI?

Wed Nov 02, 2011 12:07 pm

@abishur solution was to cut one of the two USB out of the RasPi power circuit then jump a cord to the micro USB power connector, or solder into the board directly. Then you avoid any of these possible fights and reduce the chances of the magic blue smoke dramatically. He also was going to modify the hub to send power over the link port which are usually unpowered from the hub side.
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