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8095 Posts

11-19-2007

United States of America

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Re: TPT2 has USB port power issue

2013-01-22, 18:03 PM

All,

 

I appreciate the frustration on this, and we can certainly narrow the concerns down to focus on the degree of support for unpowered devices.  However, my approach here was to look at the whole discussion which also included comments about whether devices were seen and whether they could be booted from and to work through those as well.

 

I've see some instances where the USB driver may have crashed, so if your device is not seen, it may be helpful then then plug in a USB that you know previously works.  If it is not seen, then completely shut down and restart.  I realize this may be not be a frequent case, but just something I noted happened to me.

 

We are also publishing a more complete set of instructions for preparing a bootable USB device.  I think once those are published this week, we will then only have the unpowered device compatibility issue to address, and yes we can get our engineering involved.  Thanks for your help so far in defining the issue.

 

Thanks

 

Mark

 

 

 

 

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93 Posts

10-10-2011

USA

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Re: TPT2 has USB port power issue

2013-01-22, 18:06 PM

I have a powered USB hard drive enclosure. I have noticed that the drive will run at full speed, transferring files at a corresponding rate, for a few minutes. Then it spins down and enters into something like a power saving mode, transfering files at an abysmally slow rate.

Any idea what's going on here?

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38 Posts

01-03-2013

Lynchburg, VA

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Re: TPT2 has USB port power issue

2013-01-22, 19:00 PM

I just received my TPT2 and can also confirm that mine will not recognize my Seagate FreeAgent GoFlex 500GB HD.  Other than that, so far so good from what little i can do at work.

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8095 Posts

11-19-2007

United States of America

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Re: TPT2 has USB port power issue

2013-01-22, 21:12 PM

noxxle,

 

Can you provide some more specs on your drive?  If you look at the bottom, how many miliamps or amps ( .5 or less) @ DC 5 volt input is listed?

 

If you test transferring some small files and then larger files, can you find the general size point, or time in secs that it will work vs just powering down?   

 

bpcooper14,

 

Same question as to what the Seagate lists as required input power on the bottom?  Just curious.

 

All, 

 

Are you trying this with the tablet plugged into the charger, or just running on batteries ?  Does it make a difference in any of your cases?

 

I just tried an old IBM USB CD ROM drive from March 2000 (told you it was old).  It is a TEAC CD 210PU and it worked fine whether the tablet was plugged in or not.  The CD says it requires DC 5V and .5 A which means 500mA which is the max spec for a single USB 2.0 port.

 

Reading the power section in the USB spec published on Wikipedia ... ( and recognizing Ameridian who already cited and made these points)

http://en.wikipedia.org/wiki/Universal_Serial_Bus

 

"The USB 1.x and 2.0 specifications provide a 5 V supply on a single wire from which connected USB devices may draw power. The specification provides for no more than 5.25 V and no less than 4.75 V (5 V±5%) between the positive and negative bus power lines. For USB 3.0, the voltage supplied by low-powered hub ports is 4.45–5.25 V.[46]

A unit load is defined as 100 mA in USB 2.0, and 150 mA in USB 3.0. A device may draw a maximum of 5 unit loads (500 mA) from a port in USB 2.0; 6 (900 mA) in USB 3.0. There are two types of devices: low-power and high-power. A low-power device draws at most 1 unit load, with minimum operating voltage of 4.4 V in USB 2.0, and 4 V in USB 3.0. A high-power device draws at most the maximum number of unit loads permitted by the standard. Every device functions initially as low-power but the device may request high-power and will get it if the power is available on the providing bus.[47]

Some devices, such as high-speed external disk drives, require more than 500 mA of current[48] and therefore may have power issues if powered from just one USB 2.0 port: erratic function, failure to function, or overloading/damaging the port. Such devices may come with an external power source or a Y-shaped cable that has two USB connectors (one for power+data, the other for power only) to be plugged into a computer. With such a cable, a device can draw power from two USB ports simultaneously.[49]"

 

So, on a PC that has multiple USB ports drawing from the power bus, the shared power pool may be provide more tolerance to over current conditions on a given USB port.  With a device like the tablet 2, there is only 1 USB port so there could be less tolerance of devices that draw more than the spec of 5 X 100mA power units.

 

With this in mind, let's gather a list of the unpowered devices that you have which don't work and note what their stated input requirement on the label is.  If there are some which are listed at 500mA and still don't work, then we should concentrate our testing on those.

 

 ( I'm re-reading carefully and see ScruffR's notation on a specific Seagate model)  Thanks!

 

ScruffR,

 

How did you test the current draw?  What was your method?  

 

Thanks for your continued help.

 

Mark

 

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93 Posts

10-10-2011

USA

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Re: TPT2 has USB port power issue

2013-01-22, 22:29 PM

Mark, I'm using the Ineo Dual Bay Docking Station (I-NA321U Plus). Link below.

http://www.amazon.com/gp/product/B008NA1KVW/

 

*edit* specs: http://www.ineotechusa.com/product-na321u+_t3527VI.html

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38 Posts

01-03-2013

Lynchburg, VA

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Re: TPT2 has USB port power issue

2013-01-23, 1:33 AM

Mark. Thanks for the quick response.  I can't find any information on the drive for current draw. You can look up the specs online I'm sure. The information I included was the model, drive size, etc. I tried with the TPT2 connected to a power source and without and had the same result. The drive blinks and beeps (apparently indicating not enough power to initialize)

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135 Posts

01-19-2013

Austria

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Re: TPT2 has USB port power issue

2013-01-23, 2:12 AM

Hi Mark,

 

I see now we are talking - a bit late for me, since I've already returned my device, but primarily because of this issue (

http://forums.lenovo.com/t5/ThinkPad-slate-tablets/TPT2-Problems-after-prolonged-sleep/m-p/979927 ).

 

But if I can help other victims to this problem, here is how I did it:

I did multiple measurements with each of three methods, to get a relativly secured result.

Common to all three methods is, that the HDD got connected to a Lenovo ThinkPad T500, to gain full function of the HDD and be sure that the USB host can't be blamed to be of obscure origin ;-)

I've fixed a USB probing cable where I got direct acces to the two USB power wires (RED Vcc, BLACK Gnd).

And I used a Tektronix storage oszilloscope.

 

  1. I used a Tektronix high precision current probe measuring the electric field produced by the current passing through the wire - this is a non intrusive, but less accurate way to measure current with an oszillograph.
  2. I inserted a high precision probing shunt (0.5 Ohms) into the black wire to produce a voltagedrop of expected up to 250mV, to probe with the oszilloscope (making sure, that the remaining voltage over the HDD itself didn't drop below 4,75V) - more precise way to measure current with oszi, but intrusive and so affecting the overall circuit.
  3. Combination of both methods. Measuring the current that passes through the circuit with inserted shunt with the Tektronix current probe again, to get some idea about the measuring error of #1 and the impact of the shunt on #2.

 

Measuring process:

After setup, I start the data acquisition on the oszi, plug in the HDD, wait till HDD is recognized by Windows, then I stop data acquisition and interpret the stored data, take note of the main results: peak current, peak current duration, avg. current on stable run. I did not take any measurements of head positioning, file reading or other HDD actions, but made sure, that the funcionality of the HDD was not impaird by my measuring setup.

 

Finally I unified all seperate measurements into one resulting average current characteristics.

 

I hope this helps.

 

 

PS: In case engeneers find a way to tweak the lacking Amps out of the USB port, they might also consider tweaking the microUSB in that sense, that it could be used - as I tried before without any success - in connection with a microUSB-USB-adapter to support Y-cable devices, too. Since they might be at it anyhow ;-)

 

 

PPS: Maybe somebody could vote for the one or other post of mine :smileywink:

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135 Posts

01-19-2013

Austria

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Re: TPT2 has USB port power issue

2013-01-23, 7:25 AM

If it would prove easier to modify the charging port, rather than the USB port, Lenovo could provide a proprietary USB-Y-adapter opening the gates for devices that acutally need more than 500mA and calming down hearts of victims to this issue.

 

Link to image

TPT2_USB_Y-adapter_small.png

 

This adapter could be plugged into both USB sockets at once, offering a full USB socket at the top and two microUSBs at the bottom, where either one can be connected to the AC supply, while the other one could still be used as a power socket for another microUSB charged device, offering an option to share a powerfull enough AC supply to drive/charge the TPT2 and up to two extra devices, or charge a mobile phone from the TPT2s battery if needed.

An additional perk might be, that the full USB does not stick out sideways from the TPT2 but up - if needed this socket could even be flexible to have it point downwards if prefered so.

 

An even  bolder suggestion might be, to build this thing full height of the TPT2 and fill the extra space with a spare battery, that could provide the extra power for TPT2 or any energy hungry USB device.

 

PS: If you find these suggestion interesting, just vote for this post - maybe Lenovo might pick up on it :smileyhappy:

 

BTW: I also was missing an indicator if the TPT2 is actually charging, and how close it was to being full. For this the camera LED could have got double use. When Windows is not on and the AC is connected, an RGB LED could be used to indicate the charging status and having it flash can be explicitly distinguished from "camera on warning".

 

 

Moderator comment: Image(s) >50KB converted to link(s). Community Rules. <- if this was stated on the upload screen, I could have provided a smaller one, too.

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391 Posts

08-25-2011

Iran, Tehran

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Re: TPT2 has USB port power issue

2013-01-23, 11:47 AM

Mark,

 

Your questions makes me wonder if Lenovo does not have any TPT2 in their inventory, and all of them is sold to us.

Man, you and your engineers just need 2-3 TPT2s and some external devices. This is a universal problem, every single TPT2 has it.

----------------------------------------------------------------
ThinkPad Tablet 2 - 367927U
ThinkPad Tablet - 183822U
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39 Posts

01-08-2009

France

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Re: TPT2 has USB port power issue

2013-01-23, 14:08 PM

I agree with you. It seems that all the current buyers of the TPT2 are like the beta testers of the device... Shouldn't Lenovo test this function before launching the TPT2...? This is much more annoying as Lenovo communicates about this USB port as a competitive difference with its competitors !

 

Is it that difficult to reproduce in Lenovo's labs the issue ? Plugging portable hard drive, dvd burner, 3G/ wifi usb key... etc.

 

Anyway, Lenovo should reward those beta testers !

 

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