Added iGas interface

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

src/o2/CMakeLists.txt

@@ -5,4 +5,5 @@ upm_mixed_module_init (NAME o2
     CPP_HDR o2.hpp
     CPP_SRC o2.cxx
     FTI_SRC o2_fti.c
+    IFACE_HDR iGas.hpp
     REQUIRES mraa)

src/o2/o2.cxx

@@ -54,3 +54,22 @@ float O2::voltageValue()
 	sensorVoltage = (sensorVoltage/201.0) * 10000.0;
 	return sensorVoltage;
 }
+
+float O2::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/o2/o2.hpp

@@ -26,6 +26,8 @@
 #include <string>
 #include <mraa/aio.h>
 
+#include <interfaces/iGas.hpp>
+
 namespace upm {
   /**
    * @brief Oxygen Gas Sensor
@@ -50,7 +52,7 @@ namespace upm {
    * @image html o2.jpg
    * @snippet o2.cxx Interesting
    */
-  class O2 {
+  class O2: virtual public iGas {
   public:
     /**
      * Grove O2 Oxygen Gas sensor constructor
@@ -69,6 +71,13 @@ namespace upm {
      */
     float voltageValue();
 
+    /**
+     * Measures O2 from the sensor
+     *
+     * @return Oxygen concentration as PPM
+     */
+    float getConcentration();
+
   private:
     mraa_aio_context m_aio;
   };