Moisture: Add C Src and Example

Changed from GroveMoisture.

Signed-off-by: Abhishek Malik <abhishek.malik@intel.com>

src/moisture/moisture.h

@@ -0,0 +1,74 @@
+/*
+ * Author: Jon Trulson <jtrulson@ics.com>
+ *         Abhishek Malik <abhishek.malik@intel.com>
+ * Copyright (c) 2016 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 <stdlib.h>
+#include <unistd.h>
+#include <string.h>
+
+#include "upm.h"
+#include "mraa/aio.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * device context
+ */
+typedef struct _moisture_context {
+    mraa_aio_context    aio;
+    uint16_t            analog_pin;
+} *moisture_context;
+
+/**
+ * Init function
+ *
+ * @param pin analog pin number
+ * @return void* pointer to the sensor struct
+ */
+moisture_context moisture_init(int pin);
+
+/**
+ * Close function
+ *
+ * @param dev pointer to the sensor structure
+ */
+void moisture_close(moisture_context dev);
+
+/**
+ * Get Moisture function.
+ *
+ * @param dev pointer to the sensor struct
+ * @param moisture pointer that will be used to store the
+ * output value from the sensor
+ */
+upm_result_t moisture_get_moisture(moisture_context dev,
+                                        int* moisture);
+
+#ifdef __cplusplus
+}
+#endif