Python Driver:
https://github.com/adafruit/Adafruit-Raspberry-Pi-Python-Code/blob/master/Adafruit_PWM_Servo_Driver/Adafruit_PWM_Servo_Driver.py

C++ Driver:
https://github.com/adafruit/Adafruit-PWM-Servo-Driver-Library/blob/master/Adafruit_PWMServoDriver.cpp