This is a very rough proof-of-concept Bluetooth keyboard wedge.  Keyboard
wedges are needed by barcode scanners and other devices to send keycodes
to the currently-focused EditText.  In Android, the only way to do this is
with a hardware HID device, or a "soft keyboard" input method.  So you
will see a lot of ugly-looking soft keyboards in Google Play designed to
work with a particular barcode scanner.

But what if you like the default Google Keyboard and you don't want to
switch to a different soft keyboard just so you can use a barcode scanner?
That's the problem this project is intended to solve.

Using an Adafruit Feather 32u4 Bluefruit LE, we can send the keystrokes to
the Bluefruit's UART service, and the custom Arduino sketch will re-send
those characters back on the HID service.

Pretty simple in concept, but kind of hard to implement, because once
the HID keyboard is connected to Android, the Bluefruit is no longer
discoverable, so we have do it in several steps:

    1. Pair the Bluefruit as an HID keyboard to the Android device,
       but don't connect yet.

    2. Connect to the Bluefruit's UART service using the Android app.

    3. Connect the Bluefruit as an HID keyboard.

    4. Send keystrokes to the UART, which are then echoed back through HID.

In the future, I can think of two ways to make this process simpler to set up:

    1. Use two separate Bluetooth devices, one for UART and one for HID,
       connected through a serial line.  Then we could connect to both
       Bluetooth devices at the same time.

    2. Have a background service that listens for HID Bluetooth connections,
       and saves the address.  When the keyboard wedge needs to be enabled,
       use the saved address to connect to the device's UART service.

Installation Instructions
-------------------------

1. Acquire an Adafruit Feather 32u4 Bluefruit LE, or similar Bluefruit device.

2. Install the Arduino IDE and the Adafruit BLE library:

   * https://learn.adafruit.com/adafruit-feather-32u4-bluefruit-le/setup
   * https://learn.adafruit.com/adafruit-feather-32u4-bluefruit-le/using-with-arduino-ide
   * https://learn.adafruit.com/adafruit-feather-32u4-bluefruit-le/installing-ble-library

3. Install the "keyboardwedge" sketch from this repository.

3. Upload the "keyboardwedge" sketch to the Bluefruit device.

4. Compile and install the "Bluefruit LE" app, which can be found in the
   "Bluefruit_LE_Connect_Android" directory.

Testing Instructions
--------------------

    1. Pair the Bluefruit as an HID keyboard to the Android device,
       but don't connect yet.  (On my device the only way to do this is
       to connect and then disconnect.)

    2. Connect to the Bluefruit's UART service using the "Bluefruit LE"
       Android app.

    3. Go back to Bluetooth settings and connect the Bluefruit as an
       HID keyboard.

    4. Go back to "Bluefruit LE" and send keystrokes to the UART service,
       which will be echoed back through HID.  You can also use the
       Arduino IDE's "Serial Monitor" to send keystrokes to the Bluefruit's
       serial port, which will also be send back through HID.

License
-------

All the source code came from Adafruit; I just modified it a little bit. Some
of the source files use the MIT license, while others use the BSD license.

Author
------

This project was conceived of and put together by Fred Long of SDG Systems, LLC.

flong@sdgsystems.com