servo_control.py

# sudo apt install libffi-dev
# sudo pip install -U pip setuptools
# sudo pip install PCA9685-driver
from pca9685_driver import Device
from time import sleep

# 0x40 from i2cdetect -y 1 (1 if Raspberry pi 2)
dev = Device(0x40)

# set the duty cycle for LED05 to 50%
dev.set_pwm(0, 400)

# set the pwm frequency (Hz)
dev.set_pwm_frequency(50)

while True:
  for i in range(200):
    j = i + 200
    dev.set_pwm(0, j)
    sleep(0.01)


  for i in range(200):
    j = 400 - i
    dev.set_pwm(0, j)
    sleep(0.01)