The MPR121 capacitive keyboard uses the MPR121 and 12 touch-sensitive pads to give a simple 'keyboard' with an output i2C The card also has four mounting holes that allows it to be used as an input system in place of the traditional buttons These keyboards function to measure the capacity of twelve points When an object approaches for the connector, it measures capacity changes. This signals the MPR121 that something has touched a 'button' Size: approx.75 * 50 * 3mm