Added getVolts() to iEMG interface and its sensors.

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

include/interfaces/iEmg.hpp

@@ -45,5 +45,12 @@ namespace upm
      * @return Muscle output as analog voltage
      */
     virtual int value() = 0;
+
+    /**
+     * Read scaled/offset voltage from the sensor
+     * 
+     * @return Measured volts
+     */
+    virtual float getVolts() = 0;
   };
 }

src/emg/emg.cxx

@@ -67,3 +67,21 @@ int EMG::value()
 	int val = mraa_aio_read(m_aio);
 	return val;
 }
+
+float EMG::getVolts()
+{
+	float val = mraa_aio_read_float(m_aio);
+	if (val < 0)
+		return val;
+
+	 /* Apply raw scale */
+    val *= this->m_scale;
+
+     /* Scale to aRef */
+    val *= this->m_aRef;
+
+    /* Apply the offset in volts */
+    val += this->m_offset;
+
+	return val;
+}

src/emg/emg.hpp

@@ -76,7 +76,15 @@ namespace upm {
      */
     virtual int value();
 
+    virtual float getVolts();
+
   private:
     mraa_aio_context m_aio;
+    /* Analog voltage reference */
+    float m_aRef = 5.0;
+    /* Scale */
+    float m_scale = 1.0;
+    /* Offset in sensor units */
+    float m_offset = 0.0;
   };
 }

src/groveemg/groveemg.cxx

@@ -67,3 +67,21 @@ int GroveEMG::value()
 	int val = mraa_aio_read(m_aio);
 	return val;
 }
+
+float GroveEMG::getVolts()
+{
+	float val = mraa_aio_read_float(m_aio);
+	if (val < 0)
+		return val;
+
+	 /* Apply raw scale */
+    val *= this->m_scale;
+
+     /* Scale to aRef */
+    val *= this->m_aRef;
+
+    /* Apply the offset in volts */
+    val += this->m_offset;
+
+	return val;
+}

src/groveemg/groveemg.hpp

@@ -77,7 +77,15 @@ namespace upm {
      */
     virtual int value();
 
+    virtual float getVolts();
+
   private:
     mraa_aio_context m_aio;
+    /* Analog voltage reference */
+    float m_aRef = 5.0;
+    /* Scale */
+    float m_scale = 1.0;
+    /* Offset in sensor units */
+    float m_offset = 0.0;
   };
 }