Add locking support when accessing the GPIO pins

energenie/__init__.py

@@ -1,5 +1,5 @@
 from __future__ import absolute_import
-from .energenie import switch_on, switch_off
+from .energenie import switch, switch_on, switch_off
 
 
-__version__ = '1.0.1'
+__version__ = '1.1.1'

energenie/energenie.py

@@ -1,58 +1,87 @@
 import RPi.GPIO as GPIO
 from time import sleep
+from fcntl import flock, LOCK_EX
 
-# The GPIO pins for the Energenie module
-BIT1 = 17
-BIT2 = 22
-BIT3 = 23
-BIT4 = 27
 
-ON_OFF_KEY = 24
+# Set default transmission duration of radio signal in seconds.
+# Setting to None or a value less than 0.25 will result in the code
+# using the minimum sane value of 0.25 seconds which is the shortest
+# possible time that one control frame can be broadcast in.
+#
+# Increasing this value may be beneficial if noise is anticipated
+# in the radio spectrum or a large distance between the transmitter
+# and sockets is expected because the transmitter will remain in a
+# constant loop broadcasting the same control frame over and over
+# again for the duration it is enabled. This can increase the chances
+# of sockets receiving a valid recognisable control frame, which has
+# not been corrupted, that can subsequently be acted upon.
+#
+DURATION = None
+
+
+# Define GPIO pins for the Energenie module.
+#
+D0 = 17
+D1 = 22
+D2 = 23
+D3 = 27
+MODSEL = 24
 ENABLE = 25
 
+# Assign all of the above into a master list. Place D3, D2, D1 and D0
+# first, in that order, for use with enumeration later on.
+#
+ALL = [D3, D2, D1, D0, MODSEL, ENABLE]
+
+
+# Codes for switching ON (True) and OFF (False) the sockets.
+#
+#   Group:    ALL       1       2       3       4
+#   D0-D3:   3210    3210    3210    3210    3210
+#
+CODES = {
+    True:  ['1011', '1111', '1110', '1101', '1100'],  # ON
+    False: ['0011', '0111', '0110', '0101', '0100'],  # OFF
+}
+
+
 GPIO.setmode(GPIO.BCM)
 GPIO.setwarnings(False)
 
-GPIO.setup(BIT1, GPIO.OUT)
-GPIO.setup(BIT2, GPIO.OUT)
-GPIO.setup(BIT3, GPIO.OUT)
-GPIO.setup(BIT4, GPIO.OUT)
-
-GPIO.setup(ON_OFF_KEY, GPIO.OUT)
-GPIO.setup(ENABLE, GPIO.OUT)
-
-GPIO.output(ON_OFF_KEY, False)
-GPIO.output(ENABLE, False)
-
-GPIO.output(BIT1, False)
-GPIO.output(BIT2, False)
-GPIO.output(BIT3, False)
-GPIO.output(BIT4, False)
-
-# Codes for switching on and off the sockets
-#       all     1       2       3       4
-ON = ['1011', '1111', '1110', '1101', '1100']
-OFF = ['0011', '0111', '0110', '0101', '0100']
-
-
-def change_plug_state(socket, on_or_off):
-    state = on_or_off[socket][3] == '1'
-    GPIO.output(BIT1, state)
-    state = on_or_off[socket][2] == '1'
-    GPIO.output(BIT2, state)
-    state = on_or_off[socket][1] == '1'
-    GPIO.output(BIT3, state)
-    state = on_or_off[socket][0] == '1'
-    GPIO.output(BIT4, state)
+
+def reset():
+    map(lambda p: GPIO.setup(p, GPIO.OUT), ALL)
+    map(lambda p: GPIO.output(p, False), ALL)
+    sleep(0.1)
+
+
+def broadcast(state, socket, duration):
+    duration = max(duration, 0.25)
+    lock = open('/run/GPIO.lock', 'a')
+    flock(lock, LOCK_EX)
+    reset()
+    try:
+        map(lambda (i, p): GPIO.output(p, CODES[state][socket][i] == '1'),
+            enumerate(ALL[:4])
+            )
+    except:
+        lock.close()
+        return
     sleep(0.1)
     GPIO.output(ENABLE, True)
-    sleep(0.25)
+    sleep(duration)
     GPIO.output(ENABLE, False)
+    reset()
+    lock.close()
+
+
+def switch(state, socket=0, duration=DURATION):
+    broadcast(bool(state), socket, duration)
 
 
-def switch_on(socket=0):
-    change_plug_state(socket, ON)
+def switch_on(socket=0, duration=DURATION):
+    switch(True, socket, duration)
 
 
-def switch_off(socket=0):
-    change_plug_state(socket, OFF)
+def switch_off(socket=0, duration=DURATION):
+    switch(False, socket, duration)