diff --git a/.travis.yml b/.travis.yml
index 0f87fad..b315707 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,6 +1,8 @@
 language: python
 python: 2.7
-install: pip install -qq flake8 pytest pytest-cov tox
+install:
+  - pip install -qq flake8 pytest pytest-cov tox
+  - python setup.py install
 script:
   - flake8 --version
   - flake8 --ignore=E501 pingo
diff --git a/README.rst b/README.rst
index 33f391e..552d6f1 100644
--- a/README.rst
+++ b/README.rst
@@ -46,11 +46,12 @@ Once you have a board instance, it's possible to access its pins through the ``b
 .. code-block:: python
 
     import pingo
+    from pingo import State, Mode
     from time import sleep
 
     board = pingo.detect.get_board()
     led_pin = board.pins[13]
-    led_pin.mode = pingo.OUT
+    led_pin.mode = Mode.OUT
 
     while True:
         led_pin.hi()
diff --git a/pingo/__init__.py b/pingo/__init__.py
index 2ad3e29..e6405ac 100644
--- a/pingo/__init__.py
+++ b/pingo/__init__.py
@@ -1,32 +1,32 @@
+from __future__ import absolute_import
+
 # api
-from board import ANALOG  # noqa
-from board import IN  # noqa
-from board import OUT  # noqa
-from board import PWM  # noqa
-from board import HIGH  # noqa
-from board import LOW  # noqa
-from board import ModeNotSuported  # noqa
-from board import WrongPinMode  # noqa
-from board import PwmOutputCapable  # noqa
-from board import AnalogInputCapable  # noqa
-from board import Board  # noqa
-from board import PwmPin  # noqa
-from board import AnalogPin  # noqa
-from board import DigitalPin  # noqa
-from board import GroundPin  # noqa
-from board import Pin  # noqa
-from board import VccPin  # noqa
-import parts  # noqa
+from .board import State  # noqa
+from .board import Mode  # noqa
+from .board import ModeNotSuported  # noqa
+from .board import WrongPinMode  # noqa
+from .board import PwmOutputCapable  # noqa
+from .board import AnalogInputCapable  # noqa
+from .board import Board  # noqa
+from .board import PwmPin  # noqa
+from .board import AnalogPin  # noqa
+from .board import DigitalPin  # noqa
+from .board import GroundPin  # noqa
+from .board import Pin  # noqa
+from .board import VccPin  # noqa
+import pingo.parts  # import * # noqa
+
 
 # boards
-import rpi  # noqa
-import ghost  # noqa
-import intel  # noqa
-import udoo  # noqa
-import pcduino  # noqa
-import arduino  # noqa
-import bbb  # noqa
+import pingo.rpi  # noqa
+import pingo.ghost  # noqa
+import pingo.intel  # noqa
+import pingo.udoo  # noqa
+import pingo.pcduino  # noqa
+import pingo.arduino  # noqa
+import pingo.bbb  # noqa
+
 
 # resources
-import detect  # noqa
-import test  # noqa
+import pingo.detect  # noqa
+import pingo.test  # noqa
diff --git a/pingo/arduino/__init__.py b/pingo/arduino/__init__.py
index 6e45239..89d4f20 100644
--- a/pingo/arduino/__init__.py
+++ b/pingo/arduino/__init__.py
@@ -1,4 +1,4 @@
-from firmata import ArduinoFirmata  # noqa
-from firmata import get_arduino  # noqa
-from pyun import YunBridge  # noqa
-from pyun import ArduinoYun  # noqa
+from .firmata import ArduinoFirmata  # noqa
+from .firmata import get_arduino  # noqa
+from .pyun import YunBridge  # noqa
+from .pyun import ArduinoYun  # noqa
diff --git a/pingo/arduino/firmata.py b/pingo/arduino/firmata.py
index eb1e5ea..37984ea 100644
--- a/pingo/arduino/firmata.py
+++ b/pingo/arduino/firmata.py
@@ -9,9 +9,10 @@
 
 import pingo
 from pingo.board import Board, DigitalPin, AnalogPin, PwmPin
+from pingo.board import State, Mode
 from pingo.board import AnalogInputCapable, PwmOutputCapable
 from pingo.detect import detect
-from util_firmata import pin_list_to_board_dict
+from .util_firmata import pin_list_to_board_dict
 
 PyMata = None
 
@@ -20,14 +21,14 @@
     True: 1,
     0: 0,
     1: 1,
-    pingo.LOW: 0,
-    pingo.HIGH: 1,
+    State.LOW: 0,
+    State.HIGH: 1,
 }
 
 # TODO: PyMata suports Input, Output, PWM, Servo, Encoder and Tone
 PIN_MODES = {
-    pingo.IN: 0,
-    pingo.OUT: 1,
+    Mode.IN: 0,
+    Mode.OUT: 1,
 }
 
 VERBOSE = False
diff --git a/pingo/arduino/pyun.py b/pingo/arduino/pyun.py
index 240beba..4e29fb3 100644
--- a/pingo/arduino/pyun.py
+++ b/pingo/arduino/pyun.py
@@ -47,7 +47,7 @@ def makeURL(self, command, pin, *args):
         else:
             url = self.base_url + '%s/%d' % (command, pin)
         if self.verbose:
-            print '[YunBridge] url: ', url
+            print('[YunBridge] url: %s' % url)
         return url
 
     def get(self, command, pin, *args):
diff --git a/pingo/arduino/test_util_firmata.py b/pingo/arduino/test_util_firmata.py
index 47ba150..3951b2d 100644
--- a/pingo/arduino/test_util_firmata.py
+++ b/pingo/arduino/test_util_firmata.py
@@ -1,6 +1,6 @@
 import unittest
 
-from util_firmata import pin_list_to_board_dict
+from .util_firmata import pin_list_to_board_dict
 
 
 class FirmataCapabilityDetect(unittest.TestCase):
@@ -43,12 +43,8 @@ def test_capability_response(self):
             0x7F,  # END_SYSEX (Pin delimiter)
         ]
 
-        data_arduino = list(
-            # [0x6C]  # CAPABILITY_RESPONSE
-            unavailible_pin
-            + digital_pin
-            + analog_pin
-        )
+        data_arduino = list(unavailible_pin + digital_pin + analog_pin)
+        # [0x6C]  # CAPABILITY_RESPONSE
 
         pinmap = pin_list_to_board_dict(data_arduino)
         for key in test_layout.keys():
diff --git a/pingo/bbb/__init__.py b/pingo/bbb/__init__.py
index 637b257..d4c8632 100644
--- a/pingo/bbb/__init__.py
+++ b/pingo/bbb/__init__.py
@@ -1 +1 @@
-from bbb import BeagleBoneBlack  # noqa
+from .bbb import BeagleBoneBlack  # noqa
diff --git a/pingo/board.py b/pingo/board.py
index 4a296cc..58dba5e 100644
--- a/pingo/board.py
+++ b/pingo/board.py
@@ -5,15 +5,11 @@
 from abc import ABCMeta, abstractmethod
 
 from .util import StrKeyDict
+from enum import Enum
 
-HIGH = 'HIGH'
-LOW = 'LOW'
+State = Enum('State', 'LOW HIGH')
 
-# TODO: 4 states implementation: IN, OUT, ANALOG, PWM
-IN = 'IN'
-OUT = 'OUT'
-ANALOG = 'ANALOG'
-PWM = 'PWM'
+Mode = Enum('Mode', 'IN OUT ANALOG PWM')
 
 
 class WrongPinMode(Exception):
@@ -249,8 +245,8 @@ def __repr__(self):
 
     @property
     def mode(self):
-        """[property] Get/set pin mode to ``pingo.IN``, ``pingo.OUT``
-         ``pingo.ANALOG`` or ``pingo.PWM``"""
+        """[property] Get/set pin mode to ``Mode.IN``, ``Mode.OUT``
+         ``Mode.ANALOG`` or ``Mode.PWM``"""
         return self._mode
 
     @mode.setter
@@ -258,15 +254,19 @@ def mode(self, value):
         if value not in self.suported_modes:
             raise ModeNotSuported()
 
-        if value in [IN, OUT]:
+        if value in [Mode.IN, Mode.OUT]:
             self.board._set_digital_mode(self, value)
-        elif value == ANALOG:
+        elif value == Mode.ANALOG:
             self.board._set_analog_mode(self, value)
-        elif value == PWM:
+        elif value == Mode.PWM:
             self.board._set_pwm_mode(self, value)
 
         self._mode = value
 
+    @property
+    def is_analog(self):
+        return issubclass(type(self), AnalogPin)
+
 
 class DigitalPin(Pin):
     """Defines common interface for all digital pins.
@@ -279,7 +279,7 @@ class DigitalPin(Pin):
     because pins delegate all board-dependent behavior to the board.
     """
 
-    suported_modes = [IN, OUT]
+    suported_modes = [Mode.IN, Mode.OUT]
 
     def __init__(self, board, location, gpio_id=None):
         Pin.__init__(self, board, location, gpio_id)
@@ -287,52 +287,52 @@ def __init__(self, board, location, gpio_id=None):
 
     @property
     def state(self):
-        """[property] Get/set pin state to ``pingo.HIGH`` or ``pingo.LOW``"""
-        if self.mode not in [IN, OUT]:
+        """[property] Get/set pin state to ``State.HIGH`` or ``State.LOW``"""
+        if self.mode not in [Mode.IN, Mode.OUT]:
             raise WrongPinMode()
 
-        if self.mode == IN:
+        if self.mode == Mode.IN:
             self._state = self.board._get_pin_state(self)
 
         return self._state
 
     @state.setter
     def state(self, value):
-        if self.mode != OUT:
+        if self.mode != Mode.OUT:
             raise WrongPinMode()
 
         self.board._set_pin_state(self, value)
         self._state = value
 
     def low(self):
-        """Set voltage of pin to ``pingo.LOW`` (GND)."""
-        self.state = LOW
+        """Set voltage of pin to ``State.LOW`` (GND)."""
+        self.state = State.LOW
 
     lo = low  # shortcut for interactive use
 
     def high(self):
         """Set state of the pin to ``pingo.HIGH`` (Vcc)."""
-        self.state = HIGH
+        self.state = State.HIGH
 
     hi = high  # shortcut for interactive use
 
     def toggle(self):
         """Change state of the pin."""
-        self.state = HIGH if self.state == LOW else LOW
+        self.state = State.HIGH if self.state == State.LOW else State.LOW
 
     def pulse(self):
         """Generate a pulse in state of the pin."""
-        if self.state == LOW:
-            self.state = HIGH
-            self.state = LOW
+        if self.state == State.LOW:
+            self.state = State.HIGH
+            self.state = State.LOW
         else:
-            self.state = LOW
-            self.state = HIGH
+            self.state = State.LOW
+            self.state = State.HIGH
 
 
 class PwmPin(DigitalPin):
 
-    suported_modes = [IN, OUT, PWM]
+    suported_modes = [Mode.IN, Mode.OUT, Mode.PWM]
 
     def __init__(self, board, location, gpio_id=None, frequency=None):
         DigitalPin.__init__(self, board, location, gpio_id)
@@ -344,13 +344,13 @@ def __init__(self, board, location, gpio_id=None, frequency=None):
 
     @property
     def value(self):
-        if self.mode != PWM:
+        if self.mode != Mode.PWM:
             raise WrongPinMode()
         return self.board._get_pwm_duty_cycle(self)
 
     @value.setter
     def value(self, value):
-        if self.mode != PWM:
+        if self.mode != Mode.PWM:
             raise WrongPinMode()
         if not 0.0 <= value <= 100.0:
             raise ArgumentOutOfRange()
@@ -359,13 +359,13 @@ def value(self, value):
 
     @property
     def frequency(self):
-        if self.mode != PWM:
+        if self.mode != Mode.PWM:
             raise WrongPinMode()
         return self.board._get_pwm_frequency(self)
 
     @frequency.setter
     def frequency(self, new_frequency):
-        if self.mode != PWM:
+        if self.mode != Mode.PWM:
             raise WrongPinMode()
         if new_frequency <= 0.0:
             raise ArgumentOutOfRange()
@@ -382,7 +382,7 @@ class AnalogPin(Pin):
     This pin type supports read operations only.
     """
 
-    suported_modes = [IN, ANALOG]
+    suported_modes = [Mode.IN, Mode.ANALOG]
 
     def __init__(self, board, location, resolution, gpio_id=None):
         """
diff --git a/pingo/compat.py b/pingo/compat.py
new file mode 100644
index 0000000..1fda172
--- /dev/null
+++ b/pingo/compat.py
@@ -0,0 +1,28 @@
+import sys
+
+PY2 = sys.version_info[0] == 2
+PY3 = (sys.version_info[0] >= 3)
+
+
+def iteritems(obj, **kwargs):
+    """replacement for six's iteritems for Python2/3 compat
+       uses 'iteritems' if available and otherwise uses 'items'.
+       Passes kwargs to method.
+    """
+    func = getattr(obj, "iteritems", None)
+    if not func:
+        func = obj.items
+    return func(**kwargs)
+
+
+def iterkeys(obj, **kwargs):
+    func = getattr(obj, "iterkeys", None)
+    if not func:
+        func = obj.keys
+    return func(**kwargs)
+
+
+if PY2:
+    from UserDict import UserDict  # noqa
+else:
+    from collections import UserDict  # noqa
diff --git a/pingo/detect/__init__.py b/pingo/detect/__init__.py
index 912d0a5..abd0b71 100644
--- a/pingo/detect/__init__.py
+++ b/pingo/detect/__init__.py
@@ -1,4 +1,4 @@
-from detect import get_board
+from .detect import get_board
 
 
 def has_module(module_name):
diff --git a/pingo/detect/detect.py b/pingo/detect/detect.py
index 55e9e05..c59530f 100644
--- a/pingo/detect/detect.py
+++ b/pingo/detect/detect.py
@@ -36,8 +36,7 @@ def _find_arduino_dev(system):
             return os.path.join(os.path.sep, 'dev', devices[0])
 
     elif system == 'Darwin':
-        devices = (glob.glob('/dev/tty.usbmodem*')
-                   + glob.glob('/dev/tty.usbserial*'))
+        devices = (glob.glob('/dev/tty.usbmodem*') + glob.glob('/dev/tty.usbserial*'))
         if len(devices) == 1:
             return os.path.join(os.path.sep, 'dev', devices[0])
     return False
diff --git a/pingo/detect/test_detect.py b/pingo/detect/test_detect.py
index ffc9481..659086f 100644
--- a/pingo/detect/test_detect.py
+++ b/pingo/detect/test_detect.py
@@ -2,7 +2,6 @@
 import platform
 
 import pingo
-import detect
 
 
 class DetectBasics(unittest.TestCase):
@@ -13,7 +12,7 @@ def test_board(self):
 
     @unittest.skipIf(not platform.system() == 'Linux', 'Not Linux')
     def test_read_cpu_info(self):
-        info = detect._read_cpu_info()
+        info = pingo.detect.detect._read_cpu_info()
         assert isinstance(info, dict)
 
 if __name__ == '__main__':
diff --git a/pingo/examples/analog_bars.py b/pingo/examples/analog_bars.py
index ccf9179..f733e77 100644
--- a/pingo/examples/analog_bars.py
+++ b/pingo/examples/analog_bars.py
@@ -1,11 +1,12 @@
 import pingo
+from pingo import Mode
 import time
 
 board = pingo.detect.get_board()
 # board = pingo.arduino.get_arduino()
 
 pot = board.pins['A0']
-pot.mode = pingo.ANALOG
+pot.mode = Mode.ANALOG
 
 
 def bar(pin):
diff --git a/pingo/examples/blink.py b/pingo/examples/blink.py
index f6d8b26..48e4c48 100644
--- a/pingo/examples/blink.py
+++ b/pingo/examples/blink.py
@@ -9,10 +9,11 @@
 
 import time
 import pingo
+from pingo import Mode
 
 board = pingo.detect.get_board()
 led = board.pins[13]
-led.mode = pingo.OUT
+led.mode = Mode.OUT
 
 while True:
     led.toggle()
diff --git a/pingo/examples/blink_firmata.py b/pingo/examples/blink_firmata.py
index 8565541..3bbbc4c 100644
--- a/pingo/examples/blink_firmata.py
+++ b/pingo/examples/blink_firmata.py
@@ -9,11 +9,12 @@
 
 import time
 import pingo
+from pingo import Mode
 
 ard = pingo.arduino.ArduinoFirmata('/dev/tty.usbmodemfa1341')
 print('Connected to: %s' % ard)
 led = ard.pins[13]
-led.mode = pingo.OUT
+led.mode = Mode.OUT
 
 while True:
     led.toggle()
diff --git a/pingo/examples/blink_firmata_auto.py b/pingo/examples/blink_firmata_auto.py
index 4a08c52..e56fc5b 100644
--- a/pingo/examples/blink_firmata_auto.py
+++ b/pingo/examples/blink_firmata_auto.py
@@ -9,11 +9,12 @@
 
 import time
 import pingo
+from pingo import Mode
 
 ard = pingo.arduino.get_arduino()
 print('Connected to: %s' % ard)
 led = ard.pins[13]
-led.mode = pingo.OUT
+led.mode = Mode.OUT
 
 while True:
     led.toggle()
diff --git a/pingo/examples/dimmer.py b/pingo/examples/dimmer.py
index b86db10..4ce4b68 100644
--- a/pingo/examples/dimmer.py
+++ b/pingo/examples/dimmer.py
@@ -8,20 +8,21 @@
 
 from pprint import pprint
 import pingo
+from pingo import Mode
 import time
 
 board = pingo.detect.get_board()
 
 pot = board.pins['A0']
-pot.mode = pingo.ANALOG
+pot.mode = Mode.ANALOG
 
 led = board.pins[6]
-led.mode = pingo.PWM
+led.mode = Mode.PWM
 
 display_pins = [board.pins[i] for i in range(8, 14) + [7]]
 seg_display = pingo.parts.led.SevenSegments(*display_pins)
 for pin in display_pins:
-    pin.mode = pingo.OUT
+    pin.mode = Mode.OUT
 
 
 def bar(pin):
diff --git a/pingo/examples/dojo.py b/pingo/examples/dojo.py
index e754ddd..00209f0 100644
--- a/pingo/examples/dojo.py
+++ b/pingo/examples/dojo.py
@@ -13,15 +13,16 @@
 
 import time
 import pingo
+from pingo import Mode
 
 board = pingo.detect.get_board()
 print('board: %s' % board)
 pot = board.pins['A0']
-pot.mode = pingo.ANALOG
+pot.mode = Mode.ANALOG
 leds = board.digital_pins[6:14]
 
 for led in leds:
-    led.mode = pingo.OUT
+    led.mode = Mode.OUT
     led.low()
 
 while True:
@@ -30,5 +31,5 @@
             continue
         led.high()
         time.sleep(pot.ratio())
-        print pot.ratio()
+        print(pot.ratio())
         led.low()
diff --git a/pingo/examples/dojo2.py b/pingo/examples/dojo2.py
index 9652046..037c465 100644
--- a/pingo/examples/dojo2.py
+++ b/pingo/examples/dojo2.py
@@ -12,6 +12,7 @@
 
 from time import sleep
 import pingo
+from pingo import Mode
 
 POT_LOCATION = 'A0'
 PIN_LOCATIONS = range(6, 14)
@@ -21,7 +22,7 @@
 leds = (pingo.pins[loc] for loc in PIN_LOCATIONS if loc != 9)
 
 for led in leds:
-    led.mode = pingo.OUT
+    led.mode = Mode.OUT
 
 while True:
     for led in leds:
diff --git a/pingo/examples/dojoxxl.py b/pingo/examples/dojoxxl.py
index 609a07e..fe33d14 100644
--- a/pingo/examples/dojoxxl.py
+++ b/pingo/examples/dojoxxl.py
@@ -3,10 +3,11 @@
 """
 
 import pingo
+from pingo import Mode
 import time
 
 ard = pingo.arduino.get_arduino()
-print '*' * 60
+print('*' * 60)
 
 segments = [
     11,  # A
@@ -20,17 +21,17 @@
 
 for seg in segments:
     pin = ard.pins[seg]
-    pin.mode = pingo.OUT
+    pin.mode = Mode.OUT
     pin.low()
 
 pot = ard.pins['A0']
-pot.mode = pingo.IN
+pot.mode = Mode.IN
 
 while True:
     for seg in segments:
         pin = ard.pins[seg]
         pin.high()
         delay = pot.ratio() + 0.01  # add 0.01s delay for communication
-        print '%0.3f' % delay
+        print('%0.3f' % delay)
         time.sleep(delay)
         pin.low()
diff --git a/pingo/examples/double_blink.py b/pingo/examples/double_blink.py
index 60b2a53..df8461c 100644
--- a/pingo/examples/double_blink.py
+++ b/pingo/examples/double_blink.py
@@ -10,14 +10,15 @@
 
 import time
 import pingo
+from pingo import Mode
 
 board = pingo.rpi.RaspberryPiBPlus()
 local_led = board.pins[13]
-local_led.mode = pingo.OUT
+local_led.mode = Mode.OUT
 
 ard = pingo.arduino.get_arduino()
 remote_led = ard.pins[13]
-remote_led.mode = pingo.OUT
+remote_led.mode = Mode.OUT
 
 local_led.low()  # for an common anode RGB LED
 remote_led.low()
diff --git a/pingo/examples/dual_analog_bars.py b/pingo/examples/dual_analog_bars.py
index 0660031..d9bfddc 100644
--- a/pingo/examples/dual_analog_bars.py
+++ b/pingo/examples/dual_analog_bars.py
@@ -1,20 +1,21 @@
 import pingo
 import time
+from pingo import Mode
 
 galileo = pingo.detect.get_board()
 arduino = pingo.arduino.get_arduino()
 
 pot_galileo = galileo.pins['A0']
-pot_galileo.mode = pingo.ANALOG
+pot_galileo.mode = Mode.ANALOG
 
 pot_arduino = arduino.pins['A0']
-pot_arduino.mode = pingo.ANALOG
+pot_arduino.mode = Mode.ANALOG
 
 
 def bar(pin1, pin2):
     bar1 = ('*' * int(pin1.ratio() * 40)).ljust(40)
     bar2 = ('*' * int(pin2.ratio() * 40)).rjust(40)
-    print bar2 + bar1
+    print(bar2 + bar1)
 
 while True:
     bar(pot_galileo, pot_arduino)
diff --git a/pingo/examples/galileo_analog_bars.py b/pingo/examples/galileo_analog_bars.py
index 7cc2e98..ee34605 100644
--- a/pingo/examples/galileo_analog_bars.py
+++ b/pingo/examples/galileo_analog_bars.py
@@ -1,14 +1,15 @@
-import pingo
 import time
+import pingo
+from pingo import Mode
 
 board = pingo.galileo.Galileo2()
 
 pot = board.pins['A0']
-pot.mode = pingo.ANALOG
+pot.mode = Mode.ANALOG
 
 
 def bar(pin):
-    print "*" * int(pin.ratio() * 70)
+    print("*" * int(pin.ratio() * 70))
 
 while True:
     bar(pot)
diff --git a/pingo/examples/map7segment.py b/pingo/examples/map7segment.py
index 838fdd0..4da5111 100644
--- a/pingo/examples/map7segment.py
+++ b/pingo/examples/map7segment.py
@@ -3,14 +3,15 @@
 """
 
 import pingo
+from pingo import Mode
 
 ard = pingo.arduino.get_arduino()
-print '*' * 60
+print('*' * 60)
 segs = {}
 
 for i in range(14):
     pin = ard.pins[i]
-    pin.mode = pingo.OUT
+    pin.mode = Mode.OUT
     pin.hi()
     seg = raw_input('Pin %s -> segment: ' % i).strip()
     if seg:
@@ -18,4 +19,4 @@
     pin.low()
 
 for seg, pin in sorted(segs.items()):
-    print '%s, # %s' % (pin, seg)
+    print('%s, # %s' % (pin, seg))
diff --git a/pingo/examples/parts/7seg_demo.py b/pingo/examples/parts/7seg_demo.py
index a48523a..9afd14d 100644
--- a/pingo/examples/parts/7seg_demo.py
+++ b/pingo/examples/parts/7seg_demo.py
@@ -1,7 +1,7 @@
 """ Seven segment display demo using the Garoa Dojo Shield """
 
 from time import sleep
-from pingo import OUT, detect, parts
+from pingo import Mode, detect, parts
 
 INTERVAL = 0.3
 
@@ -10,7 +10,7 @@
 display_pins = [ard.pins[i] for i in range(8, 14) + [7]]
 
 for pin in display_pins:
-    pin.mode = OUT
+    pin.mode = Mode.OUT
 
 seg_display = parts.led.SevenSegments(*display_pins)
 
diff --git a/pingo/examples/parts/led_demo.py b/pingo/examples/parts/led_demo.py
index 0641029..c6b83df 100644
--- a/pingo/examples/parts/led_demo.py
+++ b/pingo/examples/parts/led_demo.py
@@ -13,5 +13,5 @@
     a_state = '*A*' if a_led.lit else ' a '
     b_state = '*B*' if b_led.lit else ' b '
 
-    print time.strftime('%H:%M:%S'), a_state, b_state
+    print("%s %s %s" % (time.strftime('%H:%M:%S'), a_state, b_state))
     time.sleep(.1)
diff --git a/pingo/examples/pongo.py b/pingo/examples/pongo.py
index 8e9e60c..5ffb221 100644
--- a/pingo/examples/pongo.py
+++ b/pingo/examples/pongo.py
@@ -14,6 +14,7 @@
 
 import curses
 import pingo
+from pingo import Mode
 import time
 import random
 
@@ -64,10 +65,10 @@ def draw_paddle(x, y, color):
     arduino = pingo.arduino.get_arduino()
 
     pot_galileo = galileo.pins['A0']
-    pot_galileo.mode = pingo.ANALOG
+    pot_galileo.mode = Mode.ANALOG
 
     pot_arduino = arduino.pins['A0']
-    pot_arduino.mode = pingo.ANALOG
+    pot_arduino.mode = Mode.ANALOG
 
     # Read the initial values of the paddles
     paddle_1_pos = int(pot_arduino.ratio(to_min=MIN_Y, to_max=MAX_Y-PADDLE_SIZE))
diff --git a/pingo/examples/probe_pins.py b/pingo/examples/probe_pins.py
index 508b292..40eb294 100644
--- a/pingo/examples/probe_pins.py
+++ b/pingo/examples/probe_pins.py
@@ -7,6 +7,7 @@
 import sys
 
 import pingo
+from pingo import Mode
 
 
 def probe(first, last):
@@ -16,7 +17,7 @@ def probe(first, last):
     pins = board.digital_pins[first:last + 1]
 
     for pin in pins:
-        pin.mode = pingo.OUT
+        pin.mode = Mode.OUT
 
     for pin in pins:
         pin.hi()
diff --git a/pingo/examples/pwm.py b/pingo/examples/pwm.py
index e0a46e5..8d91669 100644
--- a/pingo/examples/pwm.py
+++ b/pingo/examples/pwm.py
@@ -5,14 +5,15 @@
 
 from pprint import pprint
 import pingo
+from pingo import Mode
 import time
 
-board = pingo.detect.get_board()
-print board
 
+board = pingo.detect.get_board()
+print(board)
 
 led = board.pins[6]
-led.mode = pingo.PWM
+led.mode = Mode.PWM
 
 pprint(board.pins, indent=4, width=1)
 
diff --git a/pingo/examples/rgb_led.py b/pingo/examples/rgb_led.py
index 18431af..a010e8d 100644
--- a/pingo/examples/rgb_led.py
+++ b/pingo/examples/rgb_led.py
@@ -1,13 +1,14 @@
 import time
 
 import pingo
+from pingo import Mode
 
 board = pingo.detect.get_board()
 
 rgb = [board.pins[i] for i in (11, 13, 15)]
 
 for pin in rgb:
-    pin.mode = pingo.OUT
+    pin.mode = Mode.OUT
     pin.low()
 
 while True:
diff --git a/pingo/examples/rpi_examples/display7.py b/pingo/examples/rpi_examples/display7.py
index 84f96db..06ba833 100644
--- a/pingo/examples/rpi_examples/display7.py
+++ b/pingo/examples/rpi_examples/display7.py
@@ -1,4 +1,5 @@
 import pingo
+from pingo import Mode
 import time
 
 rpi = pingo.rpi.RaspberryPi()
@@ -9,7 +10,7 @@
         if pin.location in led_locations]
 
 for pin in pins:
-    pin.mode = pingo.OUT
+    pin.mode = Mode.OUT
 
 for pin in pins:
     pin.high()
diff --git a/pingo/examples/rpi_examples/display7_anim.py b/pingo/examples/rpi_examples/display7_anim.py
index 4e61959..0699865 100644
--- a/pingo/examples/rpi_examples/display7_anim.py
+++ b/pingo/examples/rpi_examples/display7_anim.py
@@ -1,4 +1,5 @@
 import pingo
+from pingo import Mode
 from time import sleep
 
 rpi = pingo.rpi.RaspberryPi()
@@ -9,7 +10,7 @@
 pins = [rpi.pins[loc] for loc in led_locations[:6]]
 
 for pin in pins:
-    pin.mode = pingo.OUT
+    pin.mode = Mode.OUT
     pin.low()
 
 while True:
diff --git a/pingo/examples/rpi_examples/display7_probe.py b/pingo/examples/rpi_examples/display7_probe.py
index 9271cea..52df134 100644
--- a/pingo/examples/rpi_examples/display7_probe.py
+++ b/pingo/examples/rpi_examples/display7_probe.py
@@ -1,4 +1,5 @@
 import pingo
+from pingo import Mode
 
 rpi = pingo.rpi.RaspberryPi()
 
@@ -7,7 +8,7 @@
 pins = [rpi.pins[loc] for loc in led_locations]
 
 for pin in pins:
-    pin.mode = pingo.OUT
+    pin.mode = Mode.OUT
     pin.low()
 
 for pin in pins:
diff --git a/pingo/examples/rpi_examples/display7_snake.py b/pingo/examples/rpi_examples/display7_snake.py
index d20663e..e44b4c8 100644
--- a/pingo/examples/rpi_examples/display7_snake.py
+++ b/pingo/examples/rpi_examples/display7_snake.py
@@ -1,4 +1,5 @@
 import pingo
+from pingo import Mode
 from time import sleep
 
 rpi = pingo.rpi.RaspberryPi()
@@ -9,7 +10,7 @@
 pins = [rpi.pins[loc] for loc in led_sequence]
 
 for pin in pins:
-    pin.mode = pingo.OUT
+    pin.mode = Mode.OUT
     pin.low()
 
 prev_pin = pins[-1]
diff --git a/pingo/examples/switch.py b/pingo/examples/switch.py
index ed23ccc..befb435 100644
--- a/pingo/examples/switch.py
+++ b/pingo/examples/switch.py
@@ -15,13 +15,13 @@
 def show_f():
     global seg_display
     seg_display.digit = 0xF
-    print 'Fechado'  # Closed
+    print('Fechado')  # Closed
 
 
 def show_a():
     global seg_display
     seg_display.digit = 0xA
-    print 'Aberto'  # Open
+    print('Aberto')  # Open
 
 pin_sw = board.pins[3]
 my_switch = pingo.parts.Switch(pin_sw)
diff --git a/pingo/ghost/__init__.py b/pingo/ghost/__init__.py
index 220e258..9e5e17c 100644
--- a/pingo/ghost/__init__.py
+++ b/pingo/ghost/__init__.py
@@ -1 +1 @@
-from ghost import GhostBoard  # noqa
+from .ghost import GhostBoard  # noqa
diff --git a/pingo/ghost/ghost.py b/pingo/ghost/ghost.py
index 4d5a9f9..903ee33 100644
--- a/pingo/ghost/ghost.py
+++ b/pingo/ghost/ghost.py
@@ -1,4 +1,6 @@
 import pingo
+from pingo.compat import iteritems
+from pingo.board import State
 
 
 class GhostBoard(
@@ -48,7 +50,7 @@ def __init__(self, filepath=None):
         self._pin_states = pingo.util.StrKeyDict()
         # All pins start on LOW
         # FIXME: use "LOW" instead of 0
-        for location, pin in self.pins.iteritems():
+        for location, pin in iteritems(self.pins):
             self._pin_states[location] = 0 if hasattr(pin, 'state') else None
 
         # Pin 8 starts on HIGH
@@ -68,12 +70,12 @@ def _set_pwm_mode(self, pin, mode):
 
     def _set_pin_state(self, pin, state):
         print('GhostBoard: %r state -> %s' % (pin, state))
-        _state = 1 if state == pingo.HIGH else 0
+        _state = 1 if state == State.HIGH else 0
         self._pin_states[pin.location] = _state
 
     def _get_pin_state(self, pin):
         state = self._pin_states[pin.location]
-        return pingo.HIGH if state else pingo.LOW
+        return State.HIGH if state else State.LOW
 
     def _get_pin_value(self, pin):
         return self._pin_states[pin.location]
diff --git a/pingo/intel/__init__.py b/pingo/intel/__init__.py
index 3ca067b..aad7c74 100644
--- a/pingo/intel/__init__.py
+++ b/pingo/intel/__init__.py
@@ -1,2 +1,2 @@
-from intel import Galileo2  # noqa
-from intel import Edison  # noqa
+from .intel import Galileo2  # noqa
+from .intel import Edison  # noqa
diff --git a/pingo/iot/client.py b/pingo/iot/client.py
new file mode 100644
index 0000000..de0a9e0
--- /dev/null
+++ b/pingo/iot/client.py
@@ -0,0 +1,69 @@
+import json
+import pingo
+try:
+    # Python 2.7
+    from urllib2 import urlopen
+except ImportError:
+    # Python 3+
+    from urrlib.requests import urlopen
+
+
+class HTTPBoard(pingo.Board):
+    """
+    """
+
+    def __init__(self, server):
+        self.server = server
+        response = urlopen(server)
+        if response.code != 200:
+            raise Exception(u'HTTPBoard not found on server {}'.format(server))
+        response = json.load(response)
+        pins = json.loads(response['pins'])
+        gpio_pins = []
+        ground_pins = []
+        vcc_pins = []
+        pwm_pins = []
+        for pin, value in pins.items():
+            # TODO: serialize the pin (and/or the board) to do this in a better way
+            if 'GroundPin' in value:
+                ground_pins.append(pingo.GroundPin(self, pin))
+            elif 'VccPin' in value:
+                voltage = float(value[:-2].split(' ')[1])
+                vcc_pins.append(pingo.VccPin(self, pin, voltage))
+            elif 'PwmPin' in value:
+                gpio_id = value.split(' ')[1].split('@')[0]
+                pwm_pins.append(pingo.PwmPin(self, pin, gpio_id))
+            elif 'DigitalPin' in value:
+                gpio_id = value.split(' ')[1].split('@')[0]
+                gpio_pins.append(pingo.DigitalPin(self, pin, gpio_id))
+        self._add_pins(ground_pins + vcc_pins + gpio_pins + pwm_pins)
+
+    def _set_digital_mode(self, pin, mode):
+        mode = 'input' if pingo.IN else 'output'
+        url = '{server}mode/{mode}/{pin}'.format(server=self.server,
+                                                 mode=mode, pin=pin.location)
+        urlopen(url)
+
+    def _set_pin_state(self, pin, state):
+        mode = 'analog' if pin.is_analog else 'digital'
+        state = 1 if state == pingo.HIGH else 0
+        url = '{server}{mode}/{pin}/{state}'.format(server=self.server, mode=mode,
+                                                    pin=str(pin.location),
+                                                    state=str(state))
+        print(url)
+        response = urlopen(url)
+        if response.code != 200:
+            message = u'Pin {} could not be set to {}. HTTPBoard response: {}'
+            message.format(repr(pin), state, response.code)
+            raise Exception(message)
+
+    def _get_pin_state(self, pin):
+        mode = 'analog' if pin.is_analog else 'digital'
+        url = '{server}{mode}/{pin}'.format(server=self.server, mode=mode,
+                                            pin=pin.location)
+        response = urlopen(url)
+        if response.code != 200:
+            message = u'Pin {} could not be read: HTTPBoard response: {}'
+            message.format(repr(pin), response.code)
+            raise Exception(message)
+        return response['input']
diff --git a/pingo/iot/server.py b/pingo/iot/server.py
new file mode 100644
index 0000000..96a1584
--- /dev/null
+++ b/pingo/iot/server.py
@@ -0,0 +1,76 @@
+from bottle import Bottle
+import json
+import pingo
+import sys
+
+
+app = Bottle(__name__)
+board = pingo.detect.get_board()
+
+
+@app.route('/')
+def main():
+    pins = {key: repr(value) for key, value in board.pins}
+    return {
+        'board': repr(board),
+        'pins': json.dumps(pins)
+    }
+
+
+@app.route('/mode/<mode>/<pin>')
+def mode(mode, pin):
+    assert mode in ('input', 'output')
+    mode = pingo.IN if 'input' else pingo.OUT
+    pin = board.pins[pin]
+    pin.mode = mode
+
+
+@app.route('/analog')
+def analog_pins():
+    pins = {location: pin for location, pin in board.pins
+            if pin.is_analog}
+    return {'pins': str(pins)}
+
+
+@app.route('/analog/<pin>')
+def analog_input(pin):
+    pin = board.pins[pin]
+    pin.mode = pingo.IN
+    return {'input': pin.state}
+
+
+@app.route('/analog/<pin>/<signal:float>')
+def analog_output(pin, signal):
+    pin = board.pins[pin]
+    pin.mode = pingo.OUT
+    pin.value = signal
+    return {'output': signal}
+
+
+@app.route('/digital')
+def digital_pins():
+    pins = board.pins()
+    return {'pins': str(pins)}
+
+
+@app.route('/digital/<pin>')
+def digital_input(pin):
+    pin = board.pins[pin]
+    pin.mode = pingo.IN
+    return {'input': pin.state}
+
+
+@app.route('/digital/<pin>/<signal:int>')
+def digital_output(pin, signal):
+    pin = board.pins[pin]
+    pin.mode = pingo.OUT
+    pin.high() if signal else pin.low()
+    return {'output': signal}
+
+
+if __name__ == '__main__':
+    try:
+        kwargs = {'host': sys.argv[1]}
+    except IndexError:
+        kwargs = {}
+    app.run(debug=True, **kwargs)
diff --git a/pingo/parts/button.py b/pingo/parts/button.py
index ddc362c..d574efb 100644
--- a/pingo/parts/button.py
+++ b/pingo/parts/button.py
@@ -1,5 +1,6 @@
 import time
 import threading
+from pingo.board import State, Mode
 
 
 class Switch(object):
@@ -10,7 +11,7 @@ def __init__(self, pin):
         :param pin: A instance of DigitalPin
         """
         self.pin = pin
-        self.pin.mode = 'IN'
+        self.pin.mode = Mode.IN
         self.polling_task = None
         self._up_callback = lambda: None
         self._down_callback = lambda: None
@@ -56,10 +57,10 @@ def run(self):
         while self.active:
             current_state = self.switch.pin.state
             if current_state != last_state:
-                if current_state == 'HIGH':
+                if current_state == State.HIGH:
                     last_state = current_state
                     self.switch._up_callback()
-                elif current_state == 'LOW':
+                elif current_state == State.LOW:
                     last_state = current_state
                     self.switch._down_callback()
             time.sleep(0.05)
diff --git a/pingo/parts/led.py b/pingo/parts/led.py
index 3c66825..f877213 100644
--- a/pingo/parts/led.py
+++ b/pingo/parts/led.py
@@ -1,4 +1,4 @@
-import pingo
+from pingo import State, Mode
 
 import time
 import threading
@@ -7,27 +7,27 @@
 class Led(object):
     """A single LED"""
 
-    def __init__(self, pin, lit_state=pingo.HIGH):
-        """Set lit_state to pingo.LOW to turn on led by bringing
+    def __init__(self, pin, lit_state=State.HIGH):
+        """Set lit_state to State.LOW to turn on led by bringing
            cathode to low state.
 
-        :param lit_state: use pingo.HI for anode control, pingo.LOW
+        :param lit_state: use State.HIGH for anode control, State.LOW
                           for cathode control
         """
 
-        pin.mode = pingo.OUT
+        pin.mode = Mode.OUT
         self.pin = pin
         self.lit_state = lit_state
         self.blink_task = None
 
     def on(self):
-        if self.lit_state == pingo.HIGH:
+        if self.lit_state == State.HIGH:
             self.pin.high()
         else:
             self.pin.low()
 
     def off(self):
-        if self.lit_state == pingo.HIGH:
+        if self.lit_state == State.HIGH:
             self.pin.low()
         else:
             self.pin.high()
@@ -85,7 +85,7 @@ class RGBLed(object):
     pure_colors_map = dict(PURE_COLORS)
 
     def __init__(self, red_pin, green_pin, blue_pin,
-                 lit_state=pingo.LOW):
+                 lit_state=State.LOW):
         self._leds = [Led(red_pin, lit_state), Led(green_pin, lit_state),
                       Led(blue_pin, lit_state)]
 
@@ -123,6 +123,7 @@ def __init__(self, led, times, on_delay, off_delay):
         :param off_delay: delay while LED is off
         """
         self.led = led
+        self.led_pin_state_initial = self.led.pin.state
         self.active = True
         self.forever = times == 0
         self.times_remaining = times
@@ -143,7 +144,7 @@ def run(self):
             else:
                 time.sleep(self.off_delay)
         else:
-            self.led.off()
+            self.led.pin.state = self.led_pin_state_initial
             self.active = False
 
 
@@ -173,7 +174,7 @@ class SevenSegments(object):
 
     def __init__(self, pin_a, pin_b, pin_c, pin_d,
                  pin_e, pin_f, pin_g, pin_dp=None,
-                 lit_state=pingo.HIGH):
+                 lit_state=State.HIGH):
         self._leds = [Led(pin_a, lit_state), Led(pin_b, lit_state),
                       Led(pin_c, lit_state), Led(pin_d, lit_state),
                       Led(pin_e, lit_state), Led(pin_f, lit_state),
diff --git a/pingo/parts/serial/__init__.py b/pingo/parts/serial/__init__.py
index 8343f95..38fbe2e 100644
--- a/pingo/parts/serial/__init__.py
+++ b/pingo/parts/serial/__init__.py
@@ -1 +1 @@
-from lcd import LCD16x2  # noqa
+from .lcd import LCD16x2  # noqa
diff --git a/pingo/parts/spi/__init__.py b/pingo/parts/spi/__init__.py
index 847dda5..d869c3b 100644
--- a/pingo/parts/spi/__init__.py
+++ b/pingo/parts/spi/__init__.py
@@ -1 +1 @@
-from mcp3008 import Mcp3008  # noqa
+from .mcp3008 import Mcp3008  # noqa
diff --git a/pingo/parts/spi/mcp3008.py b/pingo/parts/spi/mcp3008.py
index f037255..8a30ddb 100644
--- a/pingo/parts/spi/mcp3008.py
+++ b/pingo/parts/spi/mcp3008.py
@@ -64,7 +64,7 @@ def test():
         res = ad_chip.read(1)
         volts = float(res) / 1023 * 3.3
         ticks = int(round(float(res) / 1023 * 40)) * '='
-        print display.format(count, res, volts, ticks)
+        print(display.format(count, res, volts, ticks))
         time.sleep(.2)
         count += 1
 
diff --git a/pingo/parts/test/test_switch.py b/pingo/parts/test/test_switch.py
index 085e433..c5e127f 100644
--- a/pingo/parts/test/test_switch.py
+++ b/pingo/parts/test/test_switch.py
@@ -2,12 +2,13 @@
 import unittest
 
 from pingo.parts import Switch
+from pingo.board import State, Mode
 
 
 class FakeDigitalPin(object):
     def __init__(self):
-        self.mode = 'IN'
-        self.state = 'LOW'
+        self.mode = Mode.IN
+        self.state = State.LOW
 
 
 class TestSwitch(unittest.TestCase):
@@ -23,11 +24,11 @@ def callback_down():
 
         self.my_switch.start()
         time.sleep(.1)
-        self.pin.state = 'HIGH'
+        self.pin.state = State.HIGH
         time.sleep(.1)
-        self.pin.state = 'LOW'
+        self.pin.state = State.LOW
         time.sleep(.1)
-        self.pin.state = 'HIGH'
+        self.pin.state = State.HIGH
         time.sleep(.1)
         self.my_switch.stop()
 
@@ -45,11 +46,11 @@ def callback_up():
 
         self.my_switch.start()
         time.sleep(.1)
-        self.pin.state = 'HIGH'
+        self.pin.state = State.HIGH
         time.sleep(.1)
-        self.pin.state = 'LOW'
+        self.pin.state = State.LOW
         time.sleep(.1)
-        self.pin.state = 'HIGH'
+        self.pin.state = State.HIGH
         time.sleep(.1)
 
         self.my_switch.stop()
diff --git a/pingo/pcduino/__init__.py b/pingo/pcduino/__init__.py
index 6a7c843..1198f63 100644
--- a/pingo/pcduino/__init__.py
+++ b/pingo/pcduino/__init__.py
@@ -1 +1 @@
-from pcduino import PcDuino  # noqa
+from .pcduino import PcDuino  # noqa
diff --git a/pingo/pcduino/pcduino.py b/pingo/pcduino/pcduino.py
index a24faa2..0c617e1 100644
--- a/pingo/pcduino/pcduino.py
+++ b/pingo/pcduino/pcduino.py
@@ -1,5 +1,6 @@
-from pingo.board import Board, DigitalPin, AnalogPin, IN, OUT, HIGH, LOW
+from pingo.board import Board, DigitalPin, AnalogPin
 from pingo.board import AnalogInputCapable
+from pingo.board import State, Mode
 
 
 class PcDuino(Board, AnalogInputCapable):
@@ -9,8 +10,8 @@ class PcDuino(Board, AnalogInputCapable):
     DIGITAL_PINS_PATH = '/sys/devices/virtual/misc/gpio/'
     ADC_PATH = '/proc/'
 
-    DIGITAL_PIN_MODES = {IN: '0', OUT: '1'}
-    DIGITAL_PIN_STATES = {HIGH: '1', LOW: '0'}
+    DIGITAL_PIN_MODES = {Mode.IN: '0', Mode.OUT: '1'}
+    DIGITAL_PIN_STATES = {State.HIGH: '1', State.LOW: '0'}
     LEN_DIGITAL_PINS = 14
     ANALOG_PIN_RESOLUTIONS = [6, 6, 12, 12, 12, 12]
 
@@ -40,7 +41,7 @@ def _get_pin_state(self, pin):
         sys_string = self.DIGITAL_PINS_PATH + 'pin/gpio%s' % pin.location
         with open(sys_string, 'r') as fp:
             state = fp.read().strip()
-            return HIGH if state == '1' else LOW
+            return State.HIGH if state == '1' else State.LOW
 
     def _get_pin_value(self, pin):
         sys_string = self.ADC_PATH + 'adc%s' % pin.location[1:]  # eg. A5
diff --git a/pingo/rpi/__init__.py b/pingo/rpi/__init__.py
index f6ec5ee..1169669 100644
--- a/pingo/rpi/__init__.py
+++ b/pingo/rpi/__init__.py
@@ -1,4 +1,4 @@
-from rpi import RaspberryPi  # noqa
-from rpi import RaspberryPiBPlus  # noqa
-from rpi import RaspberryPi2B  # noqa
-from grove import GrovePi  # noqa
+from .rpi import RaspberryPi  # noqa
+from .rpi import RaspberryPiBPlus  # noqa
+from .rpi import RaspberryPi2B  # noqa
+from .grove import GrovePi  # noqa
diff --git a/pingo/test/__init__.py b/pingo/test/__init__.py
index 4ec2b54..d90a41f 100644
--- a/pingo/test/__init__.py
+++ b/pingo/test/__init__.py
@@ -1,3 +1,3 @@
-import level0  # noqa
-import level1  # noqa
-import level2  # noqa
+import pingo.test.level0  # noqa
+import pingo.test.level1  # noqa
+import pingo.test.level2  # noqa
diff --git a/pingo/test/level0/__init__.py b/pingo/test/level0/__init__.py
index 245d9e7..72c7cac 100644
--- a/pingo/test/level0/__init__.py
+++ b/pingo/test/level0/__init__.py
@@ -1,2 +1,2 @@
-from cases import BoardBasics  # noqa
-from cases import BoardExceptions  # noqa
+from .cases import BoardBasics  # noqa
+from .cases import BoardExceptions  # noqa
diff --git a/pingo/test/level0/cases.py b/pingo/test/level0/cases.py
index 6850c0d..7253660 100644
--- a/pingo/test/level0/cases.py
+++ b/pingo/test/level0/cases.py
@@ -2,6 +2,7 @@
 import unittest
 
 import pingo
+from pingo.board import Mode, State
 
 '''
 In order to use this set of cases, it is necessary to set
@@ -28,7 +29,7 @@ def test_list_pins(self):
 
     def test_led(self):
         pin = self.board.pins[self.digital_output_pin_number]
-        pin.mode = pingo.OUT
+        pin.mode = Mode.OUT
         pin.high()
 
     def test_filter(self):
@@ -41,12 +42,12 @@ def test_filter(self):
     @unittest.skip("Not automatic enough.")
     def test_button(self):
         pin = self.board.pins[self.digital_input_pin_number]
-        pin.mode = pingo.IN
-        output = pingo.LOW
+        pin.mode = Mode.IN
+        output = State.LOW
         t0 = time.time()
         delay = 5
 
-        while output == pingo.LOW:
+        while output == State.LOW:
             output = pin.state
             if time.time() - t0 > delay:
                 break
@@ -58,18 +59,18 @@ def test_button(self):
     def test_jumpwire(self):
         ''' Wire this DigitalPin directly into VDD '''
         pin = self.board.pins[self.digital_input_pin_number]
-        pin.mode = pingo.IN
+        pin.mode = Mode.IN
         output = pin.state
 
-        assert output == pingo.HIGH
+        assert output == State.HIGH
 
     def test_toggle(self):
         pin = self.board.pins[self.digital_input_pin_number]
-        pin.mode = pingo.OUT
+        pin.mode = Mode.OUT
         pin.high()
         pin.toggle()
 
-        assert pin.state == pingo.LOW
+        assert pin.state == State.LOW
 
     def test_digital_pins(self):
         digital_pins = self.board.digital_pins
@@ -94,13 +95,13 @@ def test_disabled_pin(self):
 
     def test_wrong_pin_mode_in(self):
         pin = self.board.pins[self.digital_input_pin_number]
-        pin.mode = pingo.IN
+        pin.mode = Mode.IN
 
         with self.assertRaises(pingo.WrongPinMode):
             pin.high()
 
         with self.assertRaises(pingo.WrongPinMode):
-            pin.state = pingo.HIGH
+            pin.state = State.HIGH
 
 #    def test_wrong_pin_mode_out(self):
 #        pin = self.board.pins[digital_output_pin_number]
diff --git a/pingo/test/level1/__init__.py b/pingo/test/level1/__init__.py
index 8073b13..189b11c 100644
--- a/pingo/test/level1/__init__.py
+++ b/pingo/test/level1/__init__.py
@@ -1,2 +1,2 @@
-from cases import AnalogReadBasics  # noqa
-from cases import AnalogExceptions  # noqa
+from .cases import AnalogReadBasics  # noqa
+from .cases import AnalogExceptions  # noqa
diff --git a/pingo/test/level1/cases.py b/pingo/test/level1/cases.py
index 970bd79..06641bb 100644
--- a/pingo/test/level1/cases.py
+++ b/pingo/test/level1/cases.py
@@ -1,4 +1,5 @@
 import pingo
+from pingo.board import Mode
 
 '''
 In order to use this set of cases, it is necessary to set
@@ -18,7 +19,7 @@ class AnalogReadBasics(object):
 
     def test_200ohmRead(self):
         pin = self.board.pins[self.analog_input_pin_number]
-        pin.mode = pingo.ANALOG
+        pin.mode = Mode.ANALOG
         _input = pin.value
         # print "Value Read: ", _input
 
@@ -26,7 +27,7 @@ def test_200ohmRead(self):
 
     def test_pin_ratio(self):
         pin = self.board.pins[self.analog_input_pin_number]
-        pin.mode = pingo.ANALOG
+        pin.mode = Mode.ANALOG
         bits_resolution = (2 ** pin.bits) - 1
         _input = pin.ratio(0, bits_resolution, 0.0, 1.0)
         # print "Value Read: ", _input
@@ -40,4 +41,4 @@ class AnalogExceptions(object):
     def test_wrong_output_mode(self):
         pin = self.board.pins[self.analog_input_pin_number]
         with self.assertRaises(pingo.ModeNotSuported):
-            pin.mode = pingo.OUT
+            pin.mode = Mode.OUT
diff --git a/pingo/test/level2/__init__.py b/pingo/test/level2/__init__.py
index 4d955af..a82daca 100644
--- a/pingo/test/level2/__init__.py
+++ b/pingo/test/level2/__init__.py
@@ -1,2 +1,2 @@
-from cases import PwmBasics  # noqa
-from cases import PwmExceptions  # noqa
+from .cases import PwmBasics  # noqa
+from .cases import PwmExceptions  # noqa
diff --git a/pingo/test/level2/cases.py b/pingo/test/level2/cases.py
index 7e7564b..72f4907 100644
--- a/pingo/test/level2/cases.py
+++ b/pingo/test/level2/cases.py
@@ -1,4 +1,5 @@
 import pingo
+from pingo.board import Mode
 
 '''
 In order to use this set of cases, it is necessary to set
@@ -11,7 +12,7 @@ class PwmBasics(object):
 
     def test_dot50_duty_cycle(self):
         pin = self.board.pins[self.pwm_pin_number]
-        pin.mode = pingo.PWM
+        pin.mode = Mode.PWM
         pin.value = 0.50
 
         _duty_cycle = pin.value
@@ -21,7 +22,7 @@ def test_dot50_duty_cycle(self):
 
     def test_frequency(self):
         pin = self.board.pins[self.pwm_pin_number]
-        pin.mode = pingo.PWM
+        pin.mode = Mode.PWM
         pin.frequency = 440
 
         _frequency = pin.frequency
@@ -33,11 +34,11 @@ class PwmExceptions(object):
     def test_wrong_analog_mode(self):
         pin = self.board.pins[self.pwm_pin_number]
         with self.assertRaises(pingo.ModeNotSuported):
-            pin.mode = pingo.ANALOG
+            pin.mode = Mode.ANALOG
 
     def test_wrong_read_state(self):
         pin = self.board.pins[self.pwm_pin_number]
-        pin.mode = pingo.PWM
+        pin.mode = Mode.PWM
 
         with self.assertRaises(pingo.WrongPinMode):
             pin.state
diff --git a/pingo/test_utils.py b/pingo/test_utils.py
index 3057fec..c6dcfdb 100644
--- a/pingo/test_utils.py
+++ b/pingo/test_utils.py
@@ -1,12 +1,12 @@
 import unittest
 
-import util
+from pingo.util import StrKeyDict
 
 
 class StrKeyDictTest(unittest.TestCase):
 
     def setUp(self):
-        self.d = util.StrKeyDict(
+        self.d = StrKeyDict(
             [('2', 'two'), ('4', 'four')]
         )
 
diff --git a/pingo/udoo/__init__.py b/pingo/udoo/__init__.py
index 313eae0..c981717 100644
--- a/pingo/udoo/__init__.py
+++ b/pingo/udoo/__init__.py
@@ -1 +1 @@
-from udoo import Udoo  # noqa
+from .udoo import Udoo  # noqa
diff --git a/pingo/udoo/udoo.py b/pingo/udoo/udoo.py
index 1e887ad..f49482e 100644
--- a/pingo/udoo/udoo.py
+++ b/pingo/udoo/udoo.py
@@ -8,7 +8,8 @@
 
 import os
 
-from pingo.board import Board, DigitalPin, IN, OUT, HIGH, LOW
+from pingo.board import Board, DigitalPin
+from pingo.board import State, Mode
 
 # there are no gaps in the Arduino digital pin numbering
 # of the Arduino Due embedded in the Udoo
@@ -26,8 +27,8 @@
 DIGITAL_PIN_MASK = 'gpio%d'
 DIGITAL_PIN_STATE_FILENAME = 'value'
 DIGITAL_PIN_MODE_FILENAME = 'direction'
-DIGITAL_PIN_MODES = {IN: 'in', OUT: 'out'}
-DIGITAL_PIN_STATES = {HIGH: '1', LOW: '0'}
+DIGITAL_PIN_MODES = {Mode.IN: 'in', Mode.OUT: 'out'}
+DIGITAL_PIN_STATES = {State.HIGH: '1', State.LOW: '0'}
 
 
 class Udoo(Board):
@@ -76,6 +77,6 @@ def _set_pin_state(self, pin, state):
     def cleanup(self):
         for pin in (p for p in self.pins.values()
                     if isinstance(p, DigitalPin)):
-            if pin.mode == OUT:
+            if pin.mode == Mode.OUT:
                 pin.low()
-                pin.mode = IN
+                pin.mode = Mode.IN
diff --git a/pingo/util.py b/pingo/util.py
index 985296d..5cb83f3 100644
--- a/pingo/util.py
+++ b/pingo/util.py
@@ -1,8 +1,8 @@
 import collections
-import UserDict
+from .compat import (UserDict, iterkeys)
 
 
-class StrKeyDict(UserDict.UserDict):
+class StrKeyDict(UserDict):
     """StrKeyDict always converts non-string keys to `str`
 
     Tests for item retrieval using `d[key]` notation::
@@ -67,7 +67,7 @@ def __setitem__(self, key, item):
         self.data[self.normalize(key)] = item
 
     def __iter__(self):
-        return self.iterkeys()
+        return iterkeys(self)
 
     def update(self, iterable=None, **kwds):
         if iterable is not None:
diff --git a/requirements.txt b/requirements.txt
index 444529c..267ec2f 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -15,3 +15,4 @@ pytest-cov==1.6
 pytest-pep8==1.0.6
 wsgiref==0.1.2
 pyserial==2.7
+enum34
diff --git a/scripts/vimrc b/scripts/vimrc
index 7e3f8de..00bf943 100644
--- a/scripts/vimrc
+++ b/scripts/vimrc
@@ -20,10 +20,10 @@ hi TABs ctermbg=Red ctermfg=LightRed guibg=Red guifg=LightRed term=italic
 hi TrSp ctermbg=DarkGray ctermfg=Red guibg=DarkGray guifg=Red term=italic
 call matchadd("TABs", "\t")      " All TABs but the trailing ones
 call matchadd("TrSp", "\\s\\+$") " Trailing TABs and spaces
+autocmd BufWritePre * :%s/\s\+$//e " Removes trailing spaces when save buffer
 
 " Paste mouse selected text with Shift+Insert
 if has('gui_running')
   map <S-Insert> <MiddleMouse>
   map! <S-Insert> <MiddleMouse>
 endif
-
diff --git a/setup.py b/setup.py
index 021ea66..08a7057 100644
--- a/setup.py
+++ b/setup.py
@@ -27,7 +27,7 @@ def run_tests(self):
 
 
 install_requires = [
-    '',
+    'enum34',
 ]
 
 tests_require = [