This MPR121 is a capacitive touch sensor controller driven by an I2C interface. The chip can control up to twelve

1 Channel Capacitive Touch Sesnor Module uses the touch-sensing IC TTP223 to sense the touch input thus making it easy

8 Channel Capacitive Touch Sesnor Module uses the touch-sensing IC TTP226 to sense the touch input thus making it easy

16 Channel Capacitive Touch Sesnor Module uses the touch-sensing IC TTP229 to sense the touch input thus making it easy