MPR121 Capacitive Touch Keypad Sensor Module with I2C Interface and 12 Buttons MPR121 Capacitive Keypad.
 
The MPR121 capacitive keypad uses the MPR121 microcontroller and 12 touch-sensitive pads to provide you with a simple "keyboard" with I2C output. The board also features four mounting holes, allowing it to be used as an input system in place of traditional buttons.
 
You can set up an MPR121 12-channel capacitive touch sensor with an Arduino by connecting its I2C pins and installing the Adafruit MPR121 library.
 
Wiring the MPR121 to an Arduino Uno
Most MPR121 breakout boards operate at 3.3V logic. Connect the pins as follows:
3V3 (or 3.3V) -> Arduino 3.3V pin
GND -> Arduino GND
SDA -> Arduino pin A4 (SDA)
SCL -> Arduino pin A5 (SCL)
IRQ -> Arduino digital pin 2 or 4 (optional interrupt)
 
Installing the Library and Running Code
Open your Arduino IDE.
Go to Tools > Manage Libraries....
Search for Adafruit MPR121 and click Install.
Navigate to File > Examples > Adafruit_MPR121 > MPR121test.
Select your board and port, then upload the code to your Arduino.
Open the Serial Monitor (set to 9600 baud) to see touch and release events when you touch the electrode pins (0 through 11)
 
Note:
This keypad outputs a 3.3V logic signal. If your board only accepts 5V logic signals, you will encounter problems. You will need to use a logic level converter or a board that accepts 3.3V logic signals.
 
MPR121 Module Applications:
Keyboard; Touch-sensitive buttons, touch control.
 
Resources:
1. Example Code for Arduino-TouchPad