Arduino touch controller for Windows

This project provides source code and methods to build a touch controller for Windows using Arduino Nano. This controller allows users to operate Windows applications using touch panels. The architecture of the controller is shown in the figure below.

8 metal touch panels are connected to the Arduino. When a user touches a panel, the firmware on the Arduino detects the touch state and sends it to the Windows PC via serial communication. The serial-keyevent converter on the Windows PC receives the touch state and generates a virtual keyboard press event. Finally, Windows applications (e.g., game application) receives the press event.

Hardware assembly

Parts

• Arduino Nano x 1
• touch panel x 8
  • This controller uses Capacitive sensing. Therefore, the touch panel must be conductive (I used a 1.0 mm thick aluminum plate). You can cut the panel to any size you like.
• 1M ohms resistor x 8
• electric wire (to connect Arduino and touch panels)

Circuit diagram

Building software

Firmware

1. Download Arduino IDE.
2. Connect your PC and Arduino with a USB cable.
3. Open the firmware (arduino_touch_controller.ino) with Arduino IDE.
4. Select Arduino Nano in Tools>Board menu.
5. Select Arduino serial port in Tools>Port menu (you can get the port number using Windows device manager).
6. Press Ctrl+U to compile the firmware and upload it to your Arduino.

Serial-keyevent converter

1. Compile the serial-to-keyboard event converter (serial_keyevent_converter.cs) using the following command. You can use the compiler (csc) that comes with the .NET framework. If the compilation is successful, serial_keyboard_converter.exe will be generated.

   C:\Windows\Microsoft.NET\Framework\v4.0.30319\csc serial_keyevent_converter.cs
   

   Note: You may have to change the csc path because the csc path varies depending on your Windows environment.

Running

1. Connect your PC and Arduino with a USB cable.
2. Run serial_keyboard_converter.exe from the command prompt.

   serial_keyboard_converter.exe
   

3. Enter the serial port number of the Arduino (you can get the port number using Windows device manager).

   Select the serial port to which the Arduino is connected.
   #1: COM3
   #2: COM4
   #3: COM7
   Please select a number >> 3
   

4. While a panel is touched, key press events of {Q,W,E,R,T,U,I,O} will be published on Windows. For example, you can see the characters being typed into a text editor. You can also play games with this controller by changing the key bindings of the game application.
5. Pressing enter in the command prompt will exit the serial_keyboard_converter.exe.

Settings

Adjusting firmware variables

• If the controller does not work well, you need to adjust the variables in the firmware (arduino_touch_controller.ino).

THRESHOLD_COUNT_UNTOUCH

• The reconfirmation count to transition to non-touch state.
  • Increasing this value will stabilize the detection of continuous touches.
  • Decreasing this value will reduce the delay in detecting non-touch status (however, this is not important for most applications).

CHARGE_TIME_MICRO_SECOND

• The charging time for finger capacitors.
  • Increasing this value will make it easier to detect touches, but it increases over-detection.
  • Decreasing this value will prevents over-detection, but it makes it harder to detect touches.

Key bindings

• Key bindings can be changed by editing the KEY_ASSIGN_LIST array in serial_keyevent_converter.cs.