Added initial interfaces and some sensors implementing them

src/light/light.cxx

@@ -57,6 +57,17 @@ int Light::value()
     return (int)roundf(value);
 }
 
+float Light::getLuminance()
+{
+    float value;
+
+    if (light_get_lux(m_light, &value))
+        throw std::runtime_error(std::string(__FUNCTION__) +
+        ": light_get_normalized() failed.");
+
+    return value;
+}
+
 float Light::raw_value()
 {
     // This is a hack.  Deprecated.  Should be removed ASAP.

src/light/light.hpp

@@ -28,6 +28,7 @@
 #pragma once
 
 #include <string>
+#include <interfaces/iLight.hpp>
 
 #include "light.h"
 
@@ -58,7 +59,7 @@ namespace upm {
      * @image html light.jpg
      * @snippet light.cxx Interesting
      */
-    class Light {
+    class Light : virtual public iLight {
     public:
         /**
          * Analog light sensor constructor
@@ -91,6 +92,14 @@ namespace upm {
          */
         int value();
 
+        /**
+         * Gets an approximate light value in lux from the sensor
+         *
+         * @return Approximate light reading in lux
+         * @throws std::runtime_error on error
+         */
+        virtual float getLuminance();
+
         /**
          * Set ADC reference voltage
          *