Added iGas interface

Signed-off-by: Serban Waltter <serban.waltter@rinftech.com>
Signed-off-by: Mihai Tudor Panu <mihai.tudor.panu@intel.com>

src/mg811/CMakeLists.txt

@@ -2,4 +2,5 @@ set (libname "mg811")
 set (libdescription "CO2 Sensor")
 set (module_src ${libname}.cxx)
 set (module_hpp ${libname}.hpp)
+set (module_iface iGas.hpp)
 upm_module_init(mraa)

src/mg811/mg811.cxx

@@ -88,6 +88,20 @@ float MG811::ppm()
                       (m_reactionValue / (log400-log1000))+log400);
 }
 
+float MG811::getConcentration()
+{
+  static const float log400 = log10f(400);
+  static const float log1000 = log10f(1000);
+
+  float val = volts();
+
+  if ((val / dcGain) >= m_zeroPointValue)
+    return 0.0;
+  else
+    return powf(10.0, ((val/dcGain)-m_zeroPointValue) / 
+                      (m_reactionValue / (log400-log1000))+log400);
+}
+
 bool MG811::thresholdReached()
 {
   return (m_gpio.read() ? true : false);

src/mg811/mg811.hpp

@@ -28,6 +28,8 @@
 #include <mraa/aio.hpp>
 #include <mraa/gpio.hpp>
 
+#include <interfaces/iGas.hpp>
+
 namespace upm {
   /**
    * @brief MG811 CO2 Sensor
@@ -68,7 +70,7 @@ namespace upm {
    * @snippet mg811.cxx Interesting
    */
 
-  class MG811 {
+  class MG811: virtual public iGas {
   public:
 
     /**
@@ -83,7 +85,7 @@ namespace upm {
     /**
      * MG811 destructor
      */
-    ~MG811();
+    virtual ~MG811();
 
     /**
      * Return a cumputed reference voltage to be used in calibration.
@@ -118,6 +120,7 @@ namespace upm {
      * @return The computed CO2 concentration in ppm
      */
     float ppm();
+    float getConcentration();
 
     /**
      * Read the digital pin and return true if the set threshold has