By W. H. Bell [ http://www.whbell.net/ ]
The MPR121 is present on the Adafruit Capacitive Touch HAT [ https://www.adafruit.com/product/2340 ] and the Sparkfun Capacitive Touch Sensor Breakout [ https://www.sparkfun.com/products/9695 ].
The driver uses the Python SMBus library. The installation instructions for this driver are given in the INSTALL.txt file.