light: Added light sensor C source

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

    * Renamed all files with grovelight to light
    * Replaced all instances of grovelight with light
    * Added C source for light sensor
    * Updated all cmake files
    * Added C example for light sensor
    * Split out light sensor from grove library

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

src/light/light.c

@@ -0,0 +1,131 @@
+/*
+ * 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.
+ */
+
+#include <string.h>
+#include <stdlib.h>
+#include <math.h>
+
+#include "light.h"
+
+light_context light_init(int16_t pin)
+{
+    light_context dev = (light_context) malloc(sizeof(struct _light_context));
+
+    if (dev == NULL)
+      return NULL;
+
+    /* Init aio pin */
+    dev->aio = mraa_aio_init(pin);
+
+    if (dev->aio == NULL) {
+        free(dev);
+        return NULL;
+    }
+
+    /* Set the ADC ref, scale, and offset defaults */
+    dev->m_aRef = 5.0;
+    dev->m_scale = 1.0;
+    dev->m_offset = 0.0;
+
+    return dev;
+}
+
+void light_close(light_context dev)
+{
+    mraa_aio_close(dev->aio);
+    free(dev);
+}
+
+upm_result_t light_set_aref(const light_context dev, float aref)
+{
+    dev->m_aRef = aref;
+    return UPM_SUCCESS;
+}
+
+upm_result_t light_set_scale(const light_context dev, float scale)
+{
+    dev->m_scale = scale;
+    return UPM_SUCCESS;
+}
+
+upm_result_t light_set_offset(const light_context dev, float offset)
+{
+    dev->m_offset = offset;
+    return UPM_SUCCESS;
+}
+
+float light_get_aref(const light_context dev)
+{
+    return dev->m_aRef;
+}
+
+float light_get_scale(const light_context dev)
+{
+    return dev->m_scale;
+}
+
+float light_get_offset(const light_context dev)
+{
+    return dev->m_offset;
+}
+
+upm_result_t light_get_normalized(const light_context dev, float *value)
+{
+    *value = mraa_aio_read_float(dev->aio);
+    if (*value < 0)
+        return UPM_ERROR_OPERATION_FAILED;
+}
+
+upm_result_t light_get_raw_volts(const light_context dev, float *value)
+{
+    *value = mraa_aio_read_float(dev->aio);
+    if (*value < 0)
+        return UPM_ERROR_OPERATION_FAILED;
+
+    /* Scale by the ADC reference voltage */
+    *value *= dev->m_aRef;
+
+    return UPM_SUCCESS;
+}
+
+upm_result_t light_get_lux(const light_context dev, float *value)
+{
+    *value = mraa_aio_read(dev->aio);
+    if (*value < 0)
+        return UPM_ERROR_OPERATION_FAILED;
+
+    /* Get max adc value range 1023, 2047, 4095, etc... */
+    float max_adc = (1 << mraa_aio_get_bit(dev->aio)) - 1;
+
+    /* Convert the value to lux */
+    *value = 10000.0/pow(((max_adc - *value) * 10.0 / *value)*15.0,4.0/3.0);
+
+     /* Apply scale */
+    *value *= dev->m_scale;
+
+    /* Apply the offset in lux */
+    *value += dev->m_offset;
+
+    return UPM_SUCCESS;
+}