mq303a: Initial implementation of the mq303a alcohol sensor

The module implements support for the mq303a alcohol sensor.  It was
tested on the Grove Alcohol Sensor.

Signed-off-by: Jon Trulson <jtrulson@ics.com>
Signed-off-by: Zion Orent <zorent@ics.com>
Signed-off-by: Sarah Knepper <sarah.knepper@intel.com>

src/mq303a/mq303a.h

@@ -0,0 +1,79 @@
+/*
+ * Author: Jon Trulson <jtrulson@ics.com>
+ * Copyright (c) 2014 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 <string>
+#include <mraa/aio.h>
+
+namespace upm {
+
+  /**
+   * @brief C++ API for the MQ303A Alcohol Sensor
+   *
+   * UPM module for the MQ303A Alcohol Sensor.
+   * This sensor needs to be warmed up before stable results are
+   * obtained.  The higher the value returned from value(),
+   * the higher the amount of alcohol that was detected.
+   *
+   * @ingroup analog gas alcohol
+   * @snippet mq303a.cxx Interesting
+   */
+  class MQ303A {
+  public:
+    /**
+     * MQ303A sensor constructor
+     *
+     * @param pin analog pin to use
+     * @param heaterPin digital pin mapped to analog pin to use
+     */
+    MQ303A(int pin, int heaterPin);
+
+    /**
+     * MQ303A Destructor
+     */
+    ~MQ303A();
+
+    /**
+     * Get the alcohol detected from the sensor.  
+     * The value read from the analog pin is inverted.  
+     * A higher returned value means a higher amount of alcohol was detected.
+     *
+     * @return the alcohol reading
+     */
+    int value();
+
+    /**
+     * Enable the heater.
+     *
+     * @param enable if true, enable the heater else disable
+     */
+    void heaterEnable(bool enable);
+
+  private:
+    mraa_aio_context m_aio;
+    mraa_gpio_context m_gpio;
+  };
+}
+
+