Merge pull request #22 from pdp7/master

Fix I2C init error on BeagleBone Black

Author: dhalbert

adafruit_bus_device/i2c_device.py

@@ -56,14 +56,24 @@ class I2CDevice:
  with device:
  device.write(bytes_read)
  """
+
  def __init__(self, i2c, device_address):
- # Verify that a device with that address exists.
+ """
+ Try to read a byte from an address,
+ if you get an OSError it means the device is not there
+ """
  while not i2c.try_lock():
  pass
  try:
  i2c.writeto(device_address, b'')
  except OSError:
- raise ValueError("No I2C device at address: %x" % device_address)
+ # some OS's dont like writing an empty bytesting...
+ # Retry by reading a byte
+ try:
+ result = bytearray(1)
+ i2c.readfrom_into(device_address, result)
+ except OSError:
+ raise ValueError("No I2C device at address: %x" % device_address)
  finally:
  i2c.unlock()