Refactor and bug-fixes

README.md

@@ -28,24 +28,24 @@ from emu_power import Emu
 api = Emu(synchronous=True)
 api.start_serial("/dev/tty.usbmodem146101")
 
-# This will return an instance of InstantaneousUsage, or None on timeout.
-response = api.get_instantaneous_usage()
+# This will return an instance of InstantaneousDemand, or None on timeout.
+response = api.get_instantaneous_demand()
 ```
 
 #### Asynchronous
 ```
 from emu_power import Emu
-from emu_power.response_entities import InstantaneousUsage
+from emu_power.response_entities import InstantaneousDemand
 import time
 
 api = Emu()
 api.start_serial("/dev/tty.usbmodem146101")
 
 # This will return immediately. The response data will become available
 # when the device responds.
-api.get_instantaneous_usage()
+api.get_instantaneous_demand()
 time.sleep(5)
-response = api.get_data(InstantaneousUsage)
+response = api.get_data(InstantaneousDemand)
 ```
 Note: In real programs using asynchronous mode, it would probably make sense to make
 use of the schedule function of the EMU-2. This sets the frequency that certain events

emu_power/__init__.py

@@ -1,20 +1,29 @@
-import serial
+import itertools
+import platform
 import threading
-from xml.etree import ElementTree
 import time
-import itertools
+from xml.etree import ElementTree
+
+import serial
+
 from emu_power import response_entities
 
 
-class Emu:
+if platform.system() == 'Darwin':
+    _DEFAULT_DEVICE = '/dev/tty.usbmodem11'
+elif platform.system() == 'Linux':
+    _DEFAULT_DEVICE = '/dev/ttyACM0'
+else:
+    _DEFAULT_DEVICE = None
 
+
+class Emu:
     # Construct a new Emu object. Set synchronous to true to to attempt to
     # return results synchronously if possible. Timeout is the time period
     # in seconds until a request is considered failed. Poll factor indicates
     # the fraction of a second to check for a response. Set fresh_only to True
     # to only return fresh responses from get_data. Only useful in asynchronous mode.
     def __init__(self, debug=False, fresh_only=False, synchronous=False, timeout=10, poll_factor=2):
-
         # Internal communication
         self._channel_open = False
         self._serial_port = None
@@ -39,7 +48,6 @@ def __init__(self, debug=False, fresh_only=False, synchronous=False, timeout=10,
     # Get the most recent fresh response that has come in. This
     # should be used in asynchronous mode.
     def get_data(self, klass):
-
         res = self._data.get(klass.tag_name())
         if not self.fresh_only:
             return res
@@ -51,7 +59,9 @@ def get_data(self, klass):
         return res
 
     # Open communication channel
-    def start_serial(self, port_name):
+    def start_serial(self, port_name=_DEFAULT_DEVICE):
+        assert port_name, (
+            "Must specify a port name; cannot determine default for your OS")
 
         if self._channel_open:
             return True
@@ -68,7 +78,6 @@ def start_serial(self, port_name):
 
     # Close the communication channel
     def stop_serial(self):
-
         if not self._channel_open:
             return True
 
@@ -82,7 +91,6 @@ def stop_serial(self):
     # Main communication thread - handles all asynchronous messaging
     def _communication_thread(self):
         while True:
-
             if self._stop_thread:
                 self._stop_thread = False
                 return
@@ -120,7 +128,6 @@ def _communication_thread(self):
     # unless the synchronous attribute on the library is true, in which case
     # it will return data when available, or None if the timeout has elapsed.
     def issue_command(self, command, params=None, return_class=None):
-
         if not self._channel_open:
             raise ValueError("Serial port is not open")
 
@@ -198,7 +205,7 @@ def restart(self):
         return self.issue_command('restart')
 
     # Dangerous! Will decommission device!
-    def factory_reset(self):
+    def factory_reset_warning_dangerous(self):
         return self.issue_command('factory_reset')
 
     def get_connection_status(self):
@@ -266,7 +273,6 @@ def get_message(self, mac=None, refresh=True):
         return self.issue_command('get_message', opts, return_class=response_entities.MessageCluster)
 
     def confirm_message(self, mac=None, message_id=None):
-
         if message_id is None:
             raise ValueError('Message id is required')
 
@@ -283,7 +289,6 @@ def get_current_price(self, mac=None, refresh=True):
 
     # Price is in cents, w/ decimals (e.g. "24.373")
     def set_current_price(self, mac=None, price="0.0"):
-
         parts = price.split(".", 1)
         if len(parts) == 1:
             trailing = 2

emu_power/response_entities.py

@@ -1,3 +1,5 @@
+import ctypes
+import datetime
 from xml.etree import ElementTree
 
 
@@ -30,7 +32,17 @@ def find_text(self, tag):
         return node.text
 
     def find_hex(self, text):
-        return int(self.find_text(text) or "0x00", 16)
+        """Parse hex text into a signed int32."""
+        return ctypes.c_int(int(self.find_text(text) or "0x00", 16)).value
+
+    def find_time(self, text):
+        """Parse the hex value as seconds since jan 1, 2000."""
+        time_since_2000 = self.find_hex(text)
+        if not time_since_2000:
+            return None
+
+        delta = 946684800   # seconds between jan 1, 1970 and jan 1, 2000.
+        return datetime.datetime.fromtimestamp(time_since_2000 + delta)
 
     # The root element associated with this class
     @classmethod
@@ -134,7 +146,7 @@ def _parse(self):
 class MessageCluster(Entity):
     def _parse(self):
         self.meter_mac = self.find_text("MeterMacId")
-        self.timestamp = self.find_text("TimeStamp")
+        self.timestamp = self.find_time("TimeStamp")
         self.id = self.find_text("Id")
         self.text = self.find_text("Text")
         self.confirmation_required = self.find_text("ConfirmationRequired")
@@ -149,7 +161,7 @@ def _parse(self):
 class PriceCluster(Entity):
     def _parse(self):
         self.meter_mac = self.find_text("MeterMacId")
-        self.timestamp = self.find_text("TimeStamp")
+        self.timestamp = self.find_time("TimeStamp")
         self.price = self.find_text("Price")
         self.currency = self.find_text("Currency")      # ISO-4217
         self.trailing_digits = self.find_text("TrailingDigits")
@@ -165,7 +177,7 @@ def _parse(self):
 class InstantaneousDemand(Entity):
     def _parse(self):
         self.meter_mac = self.find_text("MeterMacId")
-        self.timestamp = self.find_text("TimeStamp")
+        self.timestamp = self.find_time("TimeStamp")
         self.demand = self.find_hex("Demand")
         self.multiplier = self.find_hex("Multiplier")
         self.divisor = self.find_hex("Divisor")
@@ -183,7 +195,7 @@ def _parse(self):
 class CurrentSummationDelivered(Entity):
     def _parse(self):
         self.meter_mac = self.find_text("MeterMacId")
-        self.timestamp = self.find_text("TimeStamp")
+        self.timestamp = self.find_time("TimeStamp")
         self.summation_delivered = self.find_hex("SummationDelivered")
         self.summation_received = self.find_hex("SummationReceived")
         self.multiplier = self.find_hex("Multiplier")
@@ -202,14 +214,14 @@ def _parse(self):
 class CurrentPeriodUsage(Entity):
     def _parse(self):
         self.meter_mac = self.find_text("MeterMacId")
-        self.timestamp = self.find_text("TimeStamp")
+        self.timestamp = self.find_time("TimeStamp")
         self.current_usage = self.find_hex("CurrentUsage")
         self.multiplier = self.find_hex("Multiplier")
         self.divisor = self.find_hex("Divisor")
         self.digits_right = self.find_hex("DigitsRight")
         self.digits_left = self.find_hex("DigitsLeft")
         self.suppress_leading_zero = self.find_text("SuppressLeadingZero")
-        self.start_date = self.find_text("StartDate")
+        self.start_date = self.find_time("StartDate")
 
         # Compute actual reading (protecting from divide-by-zero)
         if self.divisor != 0:
@@ -227,8 +239,8 @@ def _parse(self):
         self.digits_right = self.find_hex("DigitsRight")
         self.digits_left = self.find_hex("DigitsLeft")
         self.suppress_leading_zero = self.find_text("SuppressLeadingZero")
-        self.start_date = self.find_text("StartDate")
-        self.end_date = self.find_text("EndDate")
+        self.start_date = self.find_time("StartDate")
+        self.end_date = self.find_time("EndDate")
 
 
 # TODO: IntervalData may appear more than once