o2: Added O2 sensor C source

Added the C source for the O2 sensor with necessary changes to cmake,
examples, docs.

    * Renamed all files with groveo2 to o2
    * Replaced all instances of groveo2 with o2
    * Added C source for o2 sensor
    * Updated all cmake files
    * Added C example for o2 sensor

Signed-off-by: Noel Eck <noel.eck@intel.com>

src/o2/o2.h

@@ -0,0 +1,135 @@
+/*
+ * Author:
+ * Copyright (c) 2015 Intel Corporation.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining
+ * a copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+ * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+ * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+#pragma once
+
+#include "upm.h"
+#include "mraa/aio.h"
+
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * device context
+ */
+typedef struct _o2_context {
+    /* mraa aio pin context */
+    mraa_aio_context aio;
+    /* Analog voltage reference */
+    float m_aRef;
+    /* Scale */
+    float m_scale;
+    /* Offset in sensor units */
+    float m_offset;
+} *o2_context;
+
+/**
+ * Initialize analog sensor
+ * @param pin is Analog pin
+ * @return sensor context as void pointer
+ */
+o2_context o2_init(int16_t pin);
+
+/**
+ * Analog sensor destructor
+ * @param sensor context pointer deallocate memory
+ */
+void o2_close(o2_context dev);
+
+/**
+ * Set sensor adc vref.
+ * @param dev sensor context pointer
+ * @param aref Voltage reference routed to ADC ref pin
+ * @return Function result code
+ */
+upm_result_t o2_set_aref(const o2_context dev, float aref);
+
+/**
+ * Get sensor adc vref
+ * @param dev sensor context pointer
+ * @return Current adc vref
+ */
+float o2_get_aref(const o2_context dev);
+
+/**
+ * Set sensor offset.  This offset is applied to the return value:
+ *     counts = counts * scale + offset * scale
+ * @param dev sensor context pointer
+ * @param offset count offset value used
+ * @return Function result code
+ */
+upm_result_t o2_set_offset(const o2_context dev, float offset);
+
+/**
+ * Get sensor offset
+ * @param dev sensor context pointer
+ * @return Current sensor offset
+ */
+float o2_get_offset(const o2_context dev);
+
+/**
+ * Set sensor scale.  This scale is applied to the return value:
+ *     counts = counts * scale + offset * scale
+ * @param dev sensor context pointer
+ * @param scale count scale value used
+ * @return Function result code
+ */
+upm_result_t o2_set_scale(const o2_context dev, float scale);
+
+/**
+ * Get sensor scale
+ * @param dev sensor context pointer
+ * @return Current sensor scale
+ */
+float o2_get_scale(const o2_context dev);
+
+/**
+ * Read raw adc counts from sensor
+ * @param dev sensor context pointer
+ * @param *value Raw adc value
+ * @return Function result code
+ */
+upm_result_t o2_get_counts(const o2_context dev, int *value);
+
+/**
+ * Read voltage from sensor
+ * @param dev sensor context pointer
+ * @param *value Voltage (v)
+ * @return Function result code
+ */
+upm_result_t o2_get_raw_volts(const o2_context dev, float *value);
+
+/**
+ * Read value from sensor
+ * @param dev sensor context pointer
+ * @param *value O2 percentage
+ * @return Function result code
+ */
+upm_result_t o2_get_value(const o2_context dev, float *value);
+
+#ifdef __cplusplus
+}
+#endif