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Copyright 2016 Google Inc.

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.


Circuit diagram and firmware of Google Japanese Input physical flick version.


  • -- this file
  • arduino/flick/* -- firmware source code (Arduino sketch)
  • circuit.png -- circuit diagram
  • photo/* -- for reference

Building your device

Electronic parts

  • Arduino Nano * 1
  • RN-42-I/RM * 1
  • SJoys 2-axes joystick module (Sainsmart) * 12
  • MCP3208 * 3
  • 0.1uF ceramic capacitor * 4
  • 470 ohm resistor * 1
  • 1k ohm resistor * 1
  • Connectors

RN42 configuration

This step is required for the first time, or when changing the device's name. See Microchip's documents for detail.

  1. Run a terminal emulator and open the serial port for Arduino.
  2. Type '!' to enter pass-through mode.
  3. Type '$$$'.
  4. Configure the module by these commands:


MY_PHYSICAL_FLICK_KEYBOARD is a device name that will appear when you scan Bluetooth devices, and can be replaced by your preferred name.

The commands will configure the module as follows:

  • 115200bps
  • Pairing mode
  • SSP "just works" mode
  • SPP profile
  • HID flag register = 0 (keyboard)

Using flick input

Power supply

When operating the device, supply power by USB cables to Arduino Nano.

Bluetooth pairing

Using your device (e.g. Android phone), scan Bluetooth devices and you will find MY_PHYSICAL_FLICK_KEYBOARD (or the name you set up) in the available device list.

After pairing, find the device in the "physical keyboard" section and choose "English - U.S." keyboard layout for it.

How to input

Switch the Japanese IME on the paired device to romaji input mode. Characters will be input as flick or press a key.

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