Self-Powered USB Host mode on the HP Touchpad

touchpad-usb-host-power

[ften] was having plenty of fun running Android on his HP Touchpad, but he soon discovered that the tablet’s micro USB port didn’t provide enough juice to his peripherals when running in host mode. He started digging around and found the perfect means of providing the extra power while maintaining the device’s stock appearance.

He pried the tablet apart and installed a small DC step up converter in an empty space located behind the Touchpad’s dummy SIM slot. After wiring the converter to the battery terminals, he installed a micro USB adapter in the empty slot, which fit perfectly after a bit of sanding.

He hacked together a USB Y-cable to pull power from his new USB jack, while retaining the existing data connection through the original USB interface. You can see the results of his work in the video below, and while [ften] hasn’t said how much his mod affects the Touchpad’s battery life, he has confirmed that it will still shut down gracefully once you inevitably sap the battery dry.

Comments

  1. Joe says:

    A USB Host mode mod…

  2. ScottInNH says:

    I can’t tell.. is this Touchpad running Android also?

    Would this USB Host mod also mean it could possibly run the Google Accessory Host mode (drive an Arduino with ADK shield)?

    I already have a nice tablet, an iPad (no troll responses please). So I don’t need a top end Droid tablet… but I do need a cheap droid tablet that will work with the Android accessory kit and Arduino shield. Apparently not all droid tablets will, besides the Galaxy, but some do exist. Might this be one? (It’s cheap! :-)

  3. Gutierrez says:

    I have Cyanogen 9 ICS on my Touchpad and it works just fine. I know host mode works for keyboards and flash drives, so it’s possible it will recognize any device the app is looking for.

    I was thinking of building an external pack that’s a battery powered hub with a micro-usb cable tacked on, but this is getting closer to what I’d really want. I don’t have much experience working with USB outside of cable and connector hacking, but shouldn’t you be able to route the juice from the DC step up to the Micro USB on the Touchpad and toss a diode or two between to stop current from going the wrong way during charging?

    I’d think you might be able to make the Y-adapter moot and just have a micro-usb to USB female adapter cord for running external drives and devices. I’d be willing to SCIENCE my Touchpad with some decent confidence I won’t fry it the moment I plug it in to charge.

  4. mechanical says:

    Perhaps I am overlooking some thing but why dont you directly feed the boosted 5V into the micro usb port and cut the old power supply connections?

    • Isaac says:

      How do you then charge the battery?

      This is actually kind of neat… although not terribly practical idea when you can just use one of those external usb boosters with the battery packs.

      • tom61 says:

        You could use the built-in inductive charger with the TouchStone dock instead using the USB cable to charge. If you want to avoid loosing USB charge/client functionality, you could route the data and sense lines (to go to host mode) to the new connector instead.

        External power packs are pretty inconvenient for a device as portable as a tablet.

  5. sniperczar says:

    Definitely going to try this with my Touchpad and see if I can’t get USB audio out to my FiiO E17 headphone amp, which pulls over 150ma even with USB charging disabled.

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