Added iGas interface

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

src/groveo2/CMakeLists.txt

@@ -2,4 +2,5 @@ set (libname "groveo2")
 set (libdescription "Oxygen (O2) Concentration Sensor")
 set (module_src ${libname}.cxx)
 set (module_hpp ${libname}.hpp)
+set (module_iface iGas.hpp)
 upm_module_init(mraa)

src/groveo2/groveo2.cxx

@@ -54,3 +54,23 @@ float GroveO2::voltageValue()
 	sensorVoltage = (sensorVoltage/201.0) * 10000.0;
 	return sensorVoltage;
 }
+
+float GroveO2::getConcentration()
+{
+  float value;
+  /* Read normalized value */
+    value = mraa_aio_read_float(m_aio);
+    if (value < 0.0)
+        return -1;
+
+    /* Convert to %oxygen
+       Datasheet for grove o2 shows a linear response for the sensor.  Assuming
+       20.5% oxygen @ 25 celsius, with an gain = 1 + 12k/100 = 121, a
+       dynamic range of 0->25% oxygen, and opamp rails of 0->3.3v (the grove o2
+       sensor uses a high-accuracy 3.3v regulator),
+     */
+    value *= 25 * 5 / 3.3;
+
+  return value;
+}
+

src/groveo2/groveo2.hpp

@@ -25,6 +25,7 @@
 
 #include <string>
 #include <mraa/aio.h>
+#include <interfaces/iGas.hpp>
 
 namespace upm {
   /**
@@ -50,7 +51,7 @@ namespace upm {
    * @image html groveo2.jpg
    * @snippet groveo2.cxx Interesting
    */
-  class GroveO2 {
+  class GroveO2: virtual public iGas {
   public:
     /**
      * Grove O2 Oxygen Gas sensor constructor
@@ -69,6 +70,13 @@ namespace upm {
      */
     float voltageValue();
 
+    /**
+     * Measures O2 from the sensor
+     *
+     * @return Oxygen concentration as PPM
+     */
+    float getConcentration();
+
   private:
     mraa_aio_context m_aio;
   };