Venue 8 - USB and Power at the same time?

Discussion in 'Dell' started by Robotica72, Nov 5, 2013.

  1. Robotica72

    Robotica72 Scribbler - Standard Member

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    I know this was discussed some in the Official Owners thread, but I thought it may be easier to ask outside that thread.

    I have tried a few cables, all that work with my Xoom / SG3 / etc ... Of course, on the Venue 8 Pro the USB portion of the Y cable works, but the power doesn't (With or without a USB device attached).

    I have tried most of the settings in the BIOS under the Southbridge settings, but nothing has helped. I remember when OTG Y cables came out on Android, you needed some tweaks to make the power / USB to work at the same time...

    Anyone tried a cable that works? Although, I think its less cable related and BIOS / OS maybe?

    Thanks!
     
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  2. dstrauss

    dstrauss Comic Relief Senior Member

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    Search the main thread, but someone has worked a hack that requires shorting the data (maybe the power) pins to the USB port once power is connected to then add a USB device - involves a two port and cable hack into the mini USB port.
     
  3. SpacePsych

    SpacePsych Pen Pal - Newbie

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    I really need to get this working reliably or else I have to send the tablet back.

    I have purchased two different OTG cables with power from amazon:
    1) http://www.amazon.com/gp/product/B009YPYORM/ref=oh_details_o01_s00_i00?ie=UTF8&psc=1
    2) http://www.amazon.com/gp/product/B00CXAC1ZW/ref=oh_details_o02_s00_i00?ie=UTF8&psc=1

    Both cables do not seem to work, it can accept a normal USB flash drive and read data, but does not charge from the Dell charger from the power side. The charger does working normally however. I have tried the splitter without plugging in the flash drive and it still doesn't work, so something in the splitter is preventing the tablet from charging or the tablet has a setting.

    Let's explore more and figure this out, obviously it's been done before on other tablets and android tablets.


    Sent from my iPad using Tapatalk HD
     
  4. dstrauss

    dstrauss Comic Relief Senior Member

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    Guys - go search the main forum - there's a guy who posted somewhere on there how to jerry-rig a two port USB connector for a computer mainboard to charge and run USB devices - real Rube Goldberg and I doubt it will ever be marketed, but it has already been cracked...
     
  5. SpacePsych

    SpacePsych Pen Pal - Newbie

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    Not sure I want to use a "jerry-rigged" device. Anyone know how that was done. Maybe there is a cable that takes advantage of what he has done already. I need a solution that won't present a "fire risk" or anything.


    Sent from my iPad using Tapatalk HD
     
  6. Mesosphere

    Mesosphere Geek. Senior Member

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    Fire safety is overrated.
     
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  7. SpacePsych

    SpacePsych Pen Pal - Newbie

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    Ha, problem is it won't be approved. This is for University use.

    I need a solution to be able to charge the tablet and connect to an external webcam and Ethernet adapter at the same time. I might have to just wait for the Venue 11 Pro or find an alternate with an additional USB port, but I would love this one to work for affordability.
     
  8. bugelrex

    bugelrex Scribbler - Standard Member

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    I've seen folks mod phones with copper wires to work with wireless chargers. Any idea how its done (safely)
     
  9. dstrauss

    dstrauss Comic Relief Senior Member

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    Guys - there is nothing short of a Dell approved part that will do what you want, and they can't even get out of their own way with accessory problems. At best it is Rube Goldberg solution because of the need to short the pins, power off, plug in your usb device, then re-power the power pins...this ain't going to happen...
     
  10. Robotica72

    Robotica72 Scribbler - Standard Member

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    I have no issues hacking something together - But in the thread all I found was a video on that, but nothing at all about any help to put one together... Nothing at all?
     
  11. dstrauss

    dstrauss Comic Relief Senior Member

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    Nothing like quoting oneself: the procedure is to short the data pins, start charging, then re-enable the data pins...
     
  12. Asylum1621

    Asylum1621 Pen Pal - Newbie

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    Yeah before dstrauss has a heart attack trying to get you to search the owner's forum let me try to explain, but be warned you're not gonna like it. Usb connectors have 4 wires, 2 outside 2 inside. The 2 outside wires are the DC supply wires, these must be connected for either charging or data transfer to work. The 2 inside wires are the data wires, say you want to plug your v8p in to a usb thumb drive, those 2 wires will be the ones transferring the data. Here's the deal though, inside of the Dell Venue 8 Pro is a simple sensing circuitry which effectively measures the resistance between the two inside pins (data wires) if their resistance is 0, (ie the pins are shorted together) then the tablet will allow charging. This means that inside of the stock charger if you were to look, the 2 outside pins would be connected to DC power and the 2 inside pins would be shorted together. The Venue Pro, when plugged in to the stock charger does a measurement, sees a short, and says OK charge. If the venue pro doesn't see a short, then it goes for data connectivity and communicates via the two (presumably unshorted) inner wires. So now that we have that established, if you wanted to say plug the venue 8 pro in to a USB hub you would need to have a switchable way of shorting together the two inner wires. You could, for instance, cut the cable halfway between the mini usb plug and regular usb plug, then take the two inner wires, strip off some material, and connect a switch between the two wires. The procedure then being, have the switch shut (short condition), plug the cable from the usb hub to the dell venue pro, it reads a short (switch shut) then starts charging, after you see that it is charging you flip the switch open, unshorting the data lines, and allowing data connectivity to your USB hub. Dell won't ever make one of these, not in a million years, in fact they designed the "check for a data short" as a means of ensuring that only authorized chargers are used, their version is that they're keeping the device safe by now allowing it to charge from a source that's gonna fry it, personally i think they do it for the money. Hope that's helpful.
     
  13. vp8

    vp8 Pen Pal - Newbie

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    Hi

    Do you think this might work to trick the VP8 to charge and host at the same time without making a custom switch?

    Take a generic OTG Y Cable, connect the main end the one with power and data to the Dell charger, connect the end to an alternate power source.

    If the Dell charger has the circuitry to short the data pins then this will put the VP8 in charge mode.

    While the power end is still connected to the alternate power source, unplug the dell charger and plug in whatever USB device you wish to use.

    I don't have a VP8 but have been following the thread from day 1 since I am very interested in getting a 8" Full Windows Tablet.

    Perhaps someone with all the right parts could try it out and see if this works.
     
  14. Robotica72

    Robotica72 Scribbler - Standard Member

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    That reply is awesome - Just needed some basic details - thinking of making something up using a PIC or Other controller to do this automatically .... Thanks again!
     
  15. dceggert

    dceggert Moving 'up' from iPAQ Senior Member

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    Maybe this idea would work instead of trying to figure out some sort of switch or daisy chained power supply:

    A custom usb cap or pigtail. Basically, use a usb cable and short the data wires. Seal off the charge wires so they do not cause issues later. This would now plug into the usb y-cable or even a usb hub connected to the y-cable. I am assuming the data cable can be shorted anywhere in the usb circuit to work (this may be a false assumption).

    To work, the y-cable with the shorting jumper would get installed and the charger connected. When the device is confirmed to be charging, pull the shorting jumper and connect your desired device. It should work at that point. No switch needed.

    Any developmental improvements?
     
  16. dstrauss

    dstrauss Comic Relief Senior Member

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    Thanks, I needed that...

    slap-goptions-thread-slap.jpg
     
  17. vp8

    vp8 Pen Pal - Newbie

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    Could you try something with the cables that you bought. Could you try capping the 'Main' USB port with the DELL Charger, but do not connect it to the wall outlet. On the smaller power split, attach another source of power such as a computer or another wallwart.

    If this charges the VP8, then unplug the Dell Charger and see if you can attach another USB device.

    We are basically using the Dell charger as a Data Pin Loop Back to trick the VP8 to go into charge mode.

    Let us know how you fare.
     
  18. SpacePsych

    SpacePsych Pen Pal - Newbie

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  19. cameld00d

    cameld00d Pen Pal - Newbie

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    Getting my v8p on Saturday and already have this exact thing setup as one of my alternatives, as well as a cable with a switch shorting the data wires. I also have the y cable with a male and female micro usb and a female standard usb. Will report back asap.
     
  20. V3D

    V3D Scribbler - Standard Member

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    Here are a couple things I want to add.
    -------------------------------------------------------

    Most USB chargers have the data pins shorted to enable fast changing on devices, Dell is not the first to use this.

    The only real risk I am currently seeing is if you managed to accidentally short the power pin +5v to the ground or data pins, that would be very bad so anyone attempting to make there own be careful.

    You can use a 1k to 2k resistor across the data pins so you don't need to use a switch.

    Using the switch on the data pins I was having issues with some high speed USB devices, using the resistor, every device I tried seemed to work normal, though even with the resistor you need to connect the cable to the tablet with power before connecting a USB device to enable charging.

    There still might be a better way than using a switch or resistor across the data pins, Micro USB has 5 pins the 5th being a sensing pin, shorting this pin to ground enables OTG (Tells the tablet to enable 5v output) some devices will go into a charge mode if there is a set amount of resistance across the 5th pin.
    I have not tried testing that with the Venue 8 Pro yet...
     
    Last edited: Nov 8, 2013

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