debian@beaglebone:/var/lib/cloud9/Adafruit_Python_PCA9685/examples$ strace -f -o strace.log python simpletest.py
Traceback (most recent call last):
  File "simpletest.py", line 21, in <module>
    pwm = Adafruit_PCA9685.PCA9685()
  File "/usr/local/lib/python2.7/dist-packages/Adafruit_PCA9685-1.0.1-py2.7.egg/Adafruit_PCA9685/PCA9685.py", line 75, in __init__
    self.set_all_pwm(0, 0)
  File "/usr/local/lib/python2.7/dist-packages/Adafruit_PCA9685-1.0.1-py2.7.egg/Adafruit_PCA9685/PCA9685.py", line 111, in set_all_pwm
    self._device.write8(ALL_LED_ON_L, on & 0xFF)
  File "build/bdist.linux-armv7l/egg/Adafruit_GPIO/I2C.py", line 116, in write8
  File "build/bdist.linux-armv7l/egg/Adafruit_PureIO/smbus.py", line 256, in write_byte_data
IOError: [Errno 16] Device or resource busy