Make backlight configurable active high/low

luma/lcd/aux.py

@@ -13,7 +13,8 @@
 @lib.rpi_gpio
 class backlight(object):
     """
-    Controls a backlight, assumed to be on GPIO 18 (PWM_CLK0) by default.
+    Controls a backlight (active low), assumed to be on GPIO 18 (PWM_CLK0) by default.
+
 
     :param gpio: GPIO interface (must be compatible with `RPi.GPIO <https://pypi.python.org/pypi/RPi.GPIO>`_).
     :param gpio_LIGHT: the GPIO pin to use for the backlight.
@@ -22,13 +23,14 @@ class backlight(object):
     :type bcm_LIGHT: int
     :raises luma.core.error.UnsupportedPlatform: GPIO access not available.
     """
-    def __init__(self, gpio=None, gpio_LIGHT=18, bcm_LIGHT=None):
+    def __init__(self, gpio=None, gpio_LIGHT=18, bcm_LIGHT=None, active_low=True):
         if bcm_LIGHT is not None:
             deprecation('bcm_LIGHT argument is deprecated in favor of gpio_LIGHT and will be removed in 1.0.0')
             gpio_LIGHT = bcm_LIGHT
 
         self._gpio_LIGHT = gpio_LIGHT
         self._gpio = gpio or self.__rpi_gpio__()
+        self._enabled = not active_low
 
         try:
             self._gpio.setmode(self._gpio.BCM)
@@ -48,4 +50,4 @@ def enable(self, value):
         """
         assert(value in [True, False])
         self._gpio.output(self._gpio_LIGHT,
-                          self._gpio.LOW if value else self._gpio.HIGH)
+                          self._enabled if value else not self._enabled)