Is it possible to program Android to act as physical USB keyboard

Question

What I really want to know is whether it is a hardware problem  or a software problem  Could I plug my android phone into a computer via USB and have it act as a hardware keyboard  I do not want to install anything on the computer  I want android to behave like the standard hardware     Edit  Clarification I want to write a program library for android that enables the device to fully emulate an ordinary keyboard  so that the operating system reports it as a standard keyboard device  and it would work in the BIOS or anywhere else that a keyboard works

User · Accepted Answer

I ve modified kernel on Nexus 7 to act like standard HID keyboard and mouse  without losing MTP ADB other USB functionality   You can use usb-gadget-test commandline utility to send keystrokes and mouse movements to your PC  I want to create a remote admin app later  which will send key events and receive video from camera   Kernel patch  binaries and instructions  https   github com pelya android-keyboard-gadget  Edit  I ve published a proper app to Google Play  if your Nexus 7 is rooted you can flash kernel right from the app  and send keypresses with it

User · Answer

Your Android already identifies with a VID PID when plugged into a host  It already has an interface for Mass Storage  You would need to hack the driver at a low level to support a 2nd interface for 03 01 HID  Then it would just be a question of pushing scancodes to the modified driver  This wouldn t be simple  but it would be a neat hack  One use would be for typing long random passwords for logins

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I believe that you can do it if you have a rooted device with a recent Android  For example  the Asus Eee Pad Transformer running Android 4 has the libraries  system lib libusb so and  system lib libusbhost so  so you can write a Java application that calls them using JNI to emulate a USB keyboard  This means that you must write some glue C code that emulates the way a USB keyboard is communicating with a PC   you must study the way the USB protocol works    I say  rooted   because some permissions are usually needed to use these libraries   Edit  The above is true when programming an Android device to act as a USB host  in your case you need to be a  gadget   I don t know how much of the Linux gadget functionality is contained in the kernel of your Android device  See this for a similar question

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Most USB keyboards need drivers to run  Any keyboard functionality  non-standard buttons  beyond the capabilities of the standard HID drivers will need to install some software on the computer   That being said  It may be possible to use Android s USB capabilities  as well as writing a custom driver if default HID is not sufficient  to achieve your goal  It is likely a very non-trivial undertaking    Edit  I think KristopherMicinski is right that the level of control you get with the stock Android USB API is inadequate for this purpose  His two solutions of modifying the firmware to communicate using HID standards  as well as a hardware middleman that translates from the Android Accessory protocol to HID both seem valid to me  If installing drivers on the computer is out of the question  these may be the only two options   However  if you re open to installing a driver for this behavior  It should be possible to write a custom driver that can handle Android USB protocol  and correctly translate to the correct calls interrupts for keyboard functionality  If memory serves  every peripheral keyboard I ve used in the last 10 years has needed to install a driver for full functionality  so this may not be considered non-standard behavior   The though just occurs that this approach will only allow the device to function as a keyboard inside windows  not during the boot process

User · Answer

Some others figured out that this is wrong  In the meantime i share their opinion  I m sorry   Old WRONG answer   In my opinion this is barely possible    Your Computer identifies any USB device with the USB device descriptor or the usb interface descriptor  To be able to use your android device as a keyboard  you would have to change these  Actually i think these are saved on a ROM in the device  so you would have to change hardware   The device needs to identifiy itself with the host even if its only charging in turned off state  has to tell usb host about the power consumption  otherwise only a few mA max   For me this points into the direction  that you would have to change hardware   Easiest  way would proabably be assemble an adapter containing a usb host chip with a   C that converts the received data  which you still had to send via usb  to ps 2 or usb-client signals that u send to the computer    In my opinion the easiest way would be  Buy one of these Keyboards you can roll and put them in your bag too

User · Answer

I have some experience here as a user  The most obvious solution is via tcp ip via a client server model  Many of the tools out there like airkeyboard  http   www freenew net iPhone air-keyboard-111 171415 htm  utilize this method for creating a keyboard mouse replacement using a smartphone os  Note that there are some security issues that become apparent in the implementation  For instance  you must be logged in to utilize the server componenents   Other cross platform tools  ie windows mac controlling another windows mac instance  utilize a similar approach  See synergy  http   synergy-foss org

User · Answer

Don t give up   Linux can do it with the right hardware  via  USB Gadgets    And giving the following facts    My old Nokia N95 could use it s USB to be a  Mass Storage Device   a  Media Player    a GSM modem   or to print photos  I can plug an iPhone into an iPad via a the Apple USB-Camera passive adapter  and they transfer pictures  iPhone can obvious present as a number of things  e g  when they go into DFU    Why is all this relevant     Because if I was writing a linux phone I know what it would do  and how it would do it   And the answer would involve USB Gadgets   Reading one of the links that was posted here       It s the Linux kernel  the code is in drivers usb gadget  in the   kernel org tree if you are interested   Android does have a few   specific gadget patches that are not in mainline  but it s not all   that much  You can see all of this by just checking out their kernel   git tree  no need to bother their developers    I would guess that you would have a shot at it - but it would involve recompiling the android kernel operating system - or at least having a build environment in which you  could  rebuild the kernel if you wanted   BTW  I have an Atmel NGW100mkII  which support USB gadgets  but doesn t ship with the HID module   And I ll be having to do the above and more

User · Answer

This is possible  without any additional drivers needed   You can emulate PC s USB keyboard with small USB dongle-sized device and then use your Android device to send keyboard  and or mouse  data over Bluetooth   Take a look on descriptive video in Indiegogo campaign  http   igg me at hiDBLUE x 3400885  BTW  The product technical documents is available here  http   www flyfish-tech com hiDBLUE

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The only way I could see this being possible is if you    modified the Android firmware to give you usb level access at a low enough level that you could operate using the necessary protocol   or   Made some sort of special hardware level converter that you attached to the device     So I suppose  depending on how much work you want to do  it could be a hardware or software problem

User · Answer

You have to establish some kind of connection to do that android-out-of-the-box  like via tcp ip and adb  so no not w o installing at least adb and a listener on the computer   But if you have an activity that sends the hardware keyboard like data via usb then why not  Won t be easy i guess  At this point the usuas forum answer comes right away   Why don t you change your plans and

User · Answer

Seems someone have done it by patching the kernel  I just came across a paper titled  Exploiting Smart-Phone USB Connectivity For Fun And Profit  by Angelos Stavrou  Zhaohui Wang  Computer Science Department George Mason University  Fairfax  VA   available freely by googling the above title   Here the two researchers are investigating the possibility of a compromised android device controlling the attached PC by having the android device presenting itself as an HID device  keyboard   As a proof of concept  it seems that they have successfully patched a kernel doing exactly what you want   They didn t provide detailed steps but anyway I just quote what they said they ve done           we developed a special USB gadget driver in addition to existing USB   composite interface on the Android Linux kernel using the USB Gadget   API for Linux 4   The UGAL framework helped us implement a simple USB   Human Interface Driver  HID  functionality  i e  device driver  and   the glue code between the various kernel APIs  Using the code provided   in     drivers usb gadget composite c     we created our own gadget driver   as an additional composite USB interface  This driver simulates a USB   keyboard device  We can also simulate a USB mouse device sending   pre-programmed input command to the desktop system  Therefore  it is   straightforward to pose as a normal USB mouse or keyboard device and   send predefined command stealthily to simulate malicious interactive   user activities  To verify this functionality  in our controlled   experiments  we send keycode sequences to perform non-fatal operations   and show how such a manipulated device can cause damages In   particular  we simulated a Dell USB keyboard  vendorID 413C    productID 2105  sending    CTRL ESC    key combination and    U    and    Enter      key sequence to reboot the machine  Notice that this only requires USB   connection and can gain the    current user    privilege on the desktop   system  With the additional local or remote exploit sent as payload    the malware can escalate the privilege and gain full access of the   desktop system

User · Answer

Looks like someone finally did it  it is a tiny bit ugly - but here it is   http   forum xda-developers com showthread php t 1871281  It involves some kernel recompiling  and a bit of editing  and you loose partial functionality  the MDC      but it s done   Personally though  now that I see the  true cost   I would probably put together a little adapter on a Teency or something - assuming that Android can talk to serial devices via USB    But that s based on the fact that I have a samsung  and would require a special cable to make a USB connection anyway - no extra pain to have a little device on the end  if I have to carry the damn cable around anyway

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I am bit late to comment in this question but it might be useful for some other people   You can make your android phone to work like keyboard  mouse  camera  sound streaming system  tethering device  In short what ever usb gadget you see in the market and until and unless hardware doesn t limit you  Such as speed  or gadget interface not available   USB device is of two type  host and gadget   So gadget device acts like client and usually has usb otg interface in most of the phones  So in gadget end  you can make your phone to behave like different device at all by switching between different configuration you are already doing it when you go into usb settings and make your device as mass storage or anything else    But for doing all these you have to modify android kernel  If you are a android device developer you can for sure do it

[android] Is it possible to program Android to act as physical USB keyboard?

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