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Lob0426
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RasPi Back-Powered through USB Hub upstream port

Wed Sep 05, 2012 1:13 am

I have been working on this project for a while now. The goal is to power and send the USB data through the same cable using the upstream port. Power is supplied by the Hub. There is only the hub power supply. In the original work I replaced the 140ma USB polyfuse with a 500ma fuse. I was seeing 4.25V at TP1/TP2. Lower than I expected. The Raspberr Pi worked just fine and I was successfully running a Wireless Keyboard/Mouse combo plus a USB HDD off of the hub. Hot plugging a USB memory stick would cause a reset.

I also modified my hub as it worked properly, it would not back-power the RasPi at all. I connected a jumper to the incoming polyfuse to the Mini USB connector. originally the jumper was on the incoming side of the fuse. I felt I might be having a problem with that also as it was a direct connection to the PSU. I moved the jumper to the outgoing side of the polyfuse so I would have a little bit of resistance.

Attemp two was with the 700ma polyfuse that used to be F3. I showed 4.35V at TP1/TP2. This also had resets when hot plugging a USB memory stick. There was still too much resistance in the circuit!

I had decided that the polfuse in the lower port (F2) plus the USB connector plus the Mini USB connector at the hub were the suspects.

Today I replaced F2 with apiece of jumper wire. I then removed the USB jack. I hardwired a USB A female off of F1. I hardwired a USB Mini male off of F2. The USB Mini alows me to disconnect the hub. When I connected the hub to the RasPi the keyboard/mouse to the hub I was reading 4.89V at TP1/TP2. I connected the USB HDD and the voltage dropped to 4.83v after entering LXDE the voltage had dropped to 4.81V. I just hot plugged the USB memory stick.

Success; No reset. Running fine!

I will add some photos of the changes in the next post.

This test could make connecting the RasPi to a Lapdock as easy as a one cable connection. It also means you do not need two PSU's plus two cables to power a RasPi plus hub. If you are already powering your RasPi from a hub port then it means one less cable.
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Lob0426
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Re: RasPi Back-Powered through USB Hub upstream port

Wed Sep 05, 2012 3:35 am

Here are a couple of pictures:

Here you can see the USB jack has been removed. This is a bottom veiw. My Thanks to @OliverJenkins; for his article on removing the USB connector.
USB jack removed.JPG
USB jack removed
USB jack removed.JPG (60.58 KiB) Viewed 11515 times
In this picture you can see that two USB cables have been hardwired to the board. The gray wire is a Mini USB connector to the hub, The black wire is a female USB port (logitech USB extender). I did not want to lose a port. You can see the jumper wire soldered in place of the polyfuse at F2. F1 has a 500ma polyfuse in place of the 140ma that came on this RasPi.
hardwired ports.JPG
cables hardwired
hardwired ports.JPG (55.59 KiB) Viewed 11515 times
512MB version 2.0 as WordPress Server
Motorola Lapdock with Pi2B
Modded Rev 1.0 with pin headers at USB

http://rich1.dyndns.tv/
(RS)Allied ships old stock to reward its Customers for long wait!

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Lob0426
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Re: RasPi Back-Powered through USB Hub upstream port

Thu Sep 06, 2012 9:16 pm

Still working on this project. Been running it through some tests to make sure it is stable setup this way. It was stable before when TP1/TP2 tested at 4.35V. Now it averages at 4.81V. The reading goes up to 4.95V if I unplug the USB HDD.
pencil box.JPG
My RasPi and hub hidden in a deaths head pencil box
pencil box.JPG (44.16 KiB) Viewed 11445 times
The gray cable is the upstream cable and is the only cable to the RasPi. The Black cable is a Female A that is currently unconnected.
running from USB hub.JPG
Running at 4.81 volts at TP1/TP2
running from USB hub.JPG (63.72 KiB) Viewed 11445 times
Just plugged in my Linksys WUSB54GC WiFi. Network Manager shows it as connected. disconnected the wired. Wifi is running off of F1 no reset. It is connected. When I attach a USB stick to that cable my voltage drops to 4.76v. I do not experience a reset while plugging or unplugging the memory stick. I also can hotplug the USB HDD without a reset. I could not hot plug anything before, so I am considering this experiment successfull at this time.

The next step will be to remove the Mini USB connector from the hub side (gray wire) and hardwire it also. Then I will remove the hub case and stack it under the RasPi. this will then be a single unit. At that time it will lose the Micro USB connector too. I could also remove F3. So basically I have 5 USB ports right now with 4 full, 2 to USB HDD, 1 for keyboard/mouse wireless combo and 1 (on RasPi) for the WiFi. The gray wire can also be used a port, but is lost when used with the hub.

I will work on it some more before next week. Really cannot wait for an A Model to try it all out with. I am worried that the new revision to the PCB could cause me to start all over. The 0ohm resistors are even gone now. So adding a little resistance back into the USB, to stop reset problems, is not going to be easy now. But it wouldn't be a challenge if it was all easy. The A model should be perfect for a Lapdock and Wifi on a single Micro USB female to A male cable. No more playing with adapter cables. I guess you could put an inline switch in the cable to turn the RasPi off.

Probably would be smarter to connect the keyboard/mouse directly to the RasPi and the WiFi to the hub. But hey its working just fine this way for now! :lol:
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Lob0426
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Re: RasPi Back-Powered through USB Hub upstream port

Tue Sep 18, 2012 6:55 pm

Well this morning I hardwired the USB hub diectly to the RasPi #1. I mounted it underneath the Audio and Composite connectors with double sided foam tape. My TP1/TP2 reading has improved to 4.91V.
everything works just fine. So now I have a Raspberry Pi with 5 USB ports available. 1 port on a dongle off of the RasPi and 4 more underneath it.

Here are some more pictures:
A side picture of the USB hub attached.
Raspi USB 64.JPG
Raspi USB 64.JPG (63.71 KiB) Viewed 11061 times
Bottom of modified hub/RasPi
raspi USB bot 64.jpg
raspi USB bot 64.jpg (60.48 KiB) Viewed 11062 times
And Finally a picture of it powered up and running with just a SD and keyboard attached.
raspi USB top 64.jpg
raspi USB top 64.jpg (60.02 KiB) Viewed 11061 times
The next step is to build a case system and do away with the double sided tape. Let the case hold it all. Also I am contemplating using one of the LM2596 boards to being this RasPi up to a 12V power system. I will adjust it to 5.25V and that should put my TP1/TP2 readinds at about 5.1V. I guarantee I will have no more power problems then. :D There is the little thing though, that I have no power problems now, but well why not.

The hub is a VANTEC go 2.0 4 port Hi-SPEED Hub. It came with a 2A power supply and was about $15 U.S.. When I removed the Mini USB connector there was just not enough room to make my connections there. The power and ground are connected up near the power connector. The Data lines were connected to the resistors that lead to the USB (uplink port) connector. That is why there are loose wires under the board. I tried for about two hours to connect to the uplink traces without success. Kept ending up with shorts. Finally threw in the towel. Getting rid of the USB connector brought my voltage just a little more also.

I thought about mounting it under the HDMI connector and removing the audio and composite. This woud put most of your connectors on two sides. On an A model you would have all of your connectors on two sides if you did this.

By the way while I was typing I have been running the board through its paces and it is working perfectly. If you really want to reduce all of those wires all over the place this really is the way to go. ;)

This poor RasPi's work is never done!
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Re: RasPi Back-Powered through USB Hub upstream port

Tue Oct 09, 2012 10:54 pm

The RasPi/Hub combo is still running perfectly.

The perfect solution would be to mount a powered hub in an injection moulded case bottom. If you designed it properly it would plug into the lower USB port on a B model or the port of an A model. You slide it into the case and onto the USB connector.

With the revision 2 PCB you would not have to make any modifications to "Back-power" a RasPi. The lower case with a hub, the upper case to lock in the RasPi and a 2A (5.25v) power adapter. Plug and run setup. This would be especially benefit the A model. This would be a very versatile setup and easy for anyone to have the extra USB ports.

An even better idea would be a keyboard case that has a built in powered hub that powers the RasPi. This would require bringing the connectors out the back or side of the keyboard enclosure. Slip in a RasPi and plug in your mouse and you are ready to go. It would be nice if there was room for a USB HDD inside also.
512MB version 2.0 as WordPress Server
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kyrenia
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Re: RasPi Back-Powered through USB Hub upstream port

Wed Oct 10, 2012 5:21 pm

Forget LM2576 use this one LM1085-5V. Tell me your opinion after use.
One Chinese 6V stabilized psu adaptor, here in Cyprus with 240V AC has 6.5V stalibized DC.
But the transformer has 11,6V AC output. DC 14,7V with LM317T.
500mA current consumption of raspberrypi means 0,5x15V-5V=5W heatsink for the regulator.

This one might work with 4-6 pi depending on the transformer.
http://www.velleman.eu/downloads/0/illu ... 3_rev1.pdf

This works well with raspberry pi. Select a suitable transformer to minimize heat.
Also this regulator LM1085-5V with just 6,5V dc input you get stabilized 5V for raspberry.

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wb2ifs
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Re: RasPi Back-Powered through USB Hub upstream port

Tue Oct 16, 2012 10:56 am

I've back-powered my "B" Pi inadvertently through my external HDD's USB plug! :D

The external HDD has a separate connection for 5V (via a coaxal to USB plug) that I've connected to a 2-port, power-only USB hub built for a car's 12V port (AKA cigarette lighter). This power-only hub is, in turn, connected to 12vdc @ 30A communications-grade power supply on my lab bench.

When I plugged the HDD's USB plug into the Pi's USB port (after powering the HDD), the PI booted up! Apparently, the cheap case I bought for the drive does not isolate its power input port from its USB plugs. (iMicro IM25COM-BK http://www.imicro.com/item.php?item=IM25COM-BK)

:idea: Since this arrangement works so well, I think I'll use in the proof-of-concept I'm building...as is! Wh00T!
Jesse Alexander, WB2IFS/3
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Lob0426
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Re: RasPi Back-Powered through USB Hub upstream port

Tue Oct 16, 2012 4:46 pm

I guess that is one way to have an USB HDD without a hub! :lol: That could be a great server setup there!
Just make sure you are between 5.25V and 4.75V at TP1/TP2. Too much could be bad, especially if it is a version 2.0 PCB, no protection at all. I had a lot less (4.25v) and the RasPi worked just fine, but I kept picking at the setup until I had the 4.75V.
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Modded Rev 1.0 with pin headers at USB

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wb2ifs
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Re: RasPi Back-Powered through USB Hub upstream port

Tue Oct 16, 2012 5:10 pm

Lob0426 wrote:I guess that is one way to have an USB HDD without a hub! :lol: That could be a great server setup there!
Just make sure you are between 5.25V and 4.75V at TP1/TP2. Too much could be bad, especially if it is a version 2.0 PCB, no protection at all. I had a lot less (4.25v) and the RasPi worked just fine, but I kept picking at the setup until I had the 4.75V.
I'm good at 4.83V. I’m running from the port on the "Compact USB Charger" (Mobile Electronics USBCC-COMPX2 http://www.amazon.com/eVogue-USBCC-comp ... B007FHZVOG) that's rated at 2.1A so I should be ok.
Jesse Alexander, WB2IFS/3
[email protected]
Twitter: @scipoet
http://www.linkedin.com/in/jessealexander
"Mastery is the ability to make that which is complex appear simple and easily understood."

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Lob0426
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Re: RasPi Back-Powered through USB Hub upstream port

Tue Oct 16, 2012 5:51 pm

Sounds like you have a good combination!
512MB version 2.0 as WordPress Server
Motorola Lapdock with Pi2B
Modded Rev 1.0 with pin headers at USB

http://rich1.dyndns.tv/
(RS)Allied ships old stock to reward its Customers for long wait!

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Lob0426
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Re: RasPi Back-Powered through USB Hub upstream port

Sun Dec 16, 2012 6:04 pm

UPDATE:
So I finally came up with a Casing solution for my 5 USB port RasPi. A modified Adafruit Vesa Mount.
adafruit vesa mod.jpg
adafruit vesa mod.jpg (59.89 KiB) Viewed 7480 times
I used the two board edge mounts that are on the sound/composite side of the RasPi as two of the mounts. I bought a board edge kit from Adafruit but they would not fit between the ports. I used a Motherboard mount instead. Nice tight fit.

My WordPress Server is running on this setup.
http://rich1.dyndns.tv
512MB version 2.0 as WordPress Server
Motorola Lapdock with Pi2B
Modded Rev 1.0 with pin headers at USB

http://rich1.dyndns.tv/
(RS)Allied ships old stock to reward its Customers for long wait!

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