grove: sliding potentiometer

Signed-off-by: Mihai Tudor Panu <mihai.t.panu@intel.com>
Signed-off-by: Brendan Le Foll <brendan.le.foll@intel.com>

src/grove/grove.cxx

@@ -160,3 +160,36 @@ float GroveRotary::rel_rad()
 {
     return GroveRotary::rel_deg() * M_PI / 180.0;
 }
+
+//// GroveSlide ////
+
+GroveSlide::GroveSlide(unsigned int pin, float ref_voltage)
+{
+    mraa_init();
+    m_aio = mraa_aio_init(pin);
+    m_ref_voltage = ref_voltage;
+    m_name = "Slide Potentiometer";
+}
+
+GroveSlide::~GroveSlide()
+{
+    mraa_aio_close(m_aio);
+}
+
+float GroveSlide::raw_value()
+{
+    return (float) mraa_aio_read(m_aio);
+}
+
+float GroveSlide::voltage_value()
+{
+    // conversion to Volts
+    float a = GroveSlide::raw_value();
+    a = m_ref_voltage * a / 1023.0 ;
+    return a;
+}
+
+float GroveSlide::ref_voltage()
+{
+    return m_ref_voltage;
+}

src/grove/grove.h

@@ -200,4 +200,51 @@ class GroveRotary: public Grove {
         static const int m_max_angle = 300;
 };
 
+/**
+ * @brief C++ API for Grove Slide Potentiometer
+ *
+ * Very basic UPM module for Grove slide potentiometer on analog,
+ * returns either raw value or scaled voltage value.
+ *
+ * @ingroup grove analog
+ * @snippet groveslide.cxx Interesting
+ * @image html groveslide.jpeg
+ */
+class GroveSlide: public Grove {
+    public:
+        /**
+         * Grove analog slide potentiometer constructor
+         *
+         * @param pin number of analog pin to use
+         *
+         * @param ref_voltage the reference voltage the board is set to as float, e.g. 3.3 or 5.0 (default)
+         */
+        GroveSlide(unsigned int pin, float ref_voltage = 5.0);
+        /**
+         * GroveSlide Destructor
+         */
+        ~GroveSlide();
+        /**
+         * Get raw value from AIO pin
+         *
+         * @return the raw value from the ADC
+         */
+        float raw_value();
+        /**
+         * Get the voltage value from the pin
+         *
+         * @return the voltage reading based on the reference voltage
+         */
+        float voltage_value();
+        /**
+         * Get the board's reference voltage passed on object initialization
+         *
+         * @return the reference voltage the class was set for
+         */
+        float ref_voltage();
+    private:
+        mraa_aio_context m_aio;
+        float m_ref_voltage;
+};
+
 }