HP Touchpad USB Host Documentation
The goal of this project is to attach USB devices such as keyboards, mice, mass storage disks and drives, and other peripherals to the HP Touchpad over its Micro-USB port.
The HP Touchpad is capable of this functionality right out of the box accept for one major caveat. The Micro-USB does not support feeding power out of the port which means you must bring your own external power to the equation.
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Overcoming the limitation of the Touchpad is easy and requires no modifications to the tablet itself meaning no voiding of the warranty and not damaging the Touchpad which is notoriously easy. Here I have constructed a cable capable of injecting power in-between the Micro-USB connector on the Touchpad and a standard USB port. Using a cheap OTG (on the go) cable and splicing into the power leads I added a small barrel jack.
Any power source can be used to provide the necessary juice to initiate the USB connection. Here I use a standard 5 volt 2 amp power supply. You may also use a portable power supply capable of providing the 5 volts, choosing a source with enough amperage ensures the Touchpad can charge while in USB Host Mode.
Using the keyboard from my Logitech Revue and a Logitech Unifying Receiver it is possible to add a wireless external keyboard and mouse to the HP Touchpad. Anything can be attached to the Touchpad, in this log I use this combo keyboard/mouse, it is also possible to attach a USB Hub to add additional USB devices.
Connecting the OTG cable to the HP touchpad, generally it is best to go ahead and plug in the USB device(s) you wish to use to the OTG cable, then power. Once you have the cable ready attach it to the HP Touchpad.
Here I use the keyboard with WebOS, unfortunately WebOS does not yet support mouses. The hardware is recognized however there is simply no mouse ui element implemented in WebOS at this time. The keyboard makes it much easier to navigate to URL's and is extremely responsive given we just attached a Logitech Revue keyboard to an HP Touchpad.
Booting into Android you find that the mouse starts working right away and makes interacting with the entire touchscreen UI possible. Here I even play some mobile MineCraft, may games support the keyboard and mouse in android however the keyboard support is not nearly as universal as in WebOS. It is up to the individual Android apps to support the keyboard.
The HP Touchpad's WebOS runs a custom Linux Kernel making it possible to chroot into another linux environment given you setup the proper partitions. There are many guides for this online and packages available through PreWare to help facilitate the installation. Here I showcase a browser plugin I developed for my previous employer HostNine, the plugin is the green circle in the top toolbar of Chromium (open source Chrome build for Linux). The plugin ties in with the Traffic Light project and pulls down status info from their internal servers. I also load up a game or two and explore a few other features of Ubuntu.