otp538u: Initial implementation

This module was tested on the Grove non-contact IR Temperature
Sensor.  The tables included are only valid for a distance of 9cm.

Signed-off-by: Jon Trulson <jtrulson@ics.com>
Signed-off-by: Zion Orent <zorent@ics.com>
Signed-off-by: John Van Drasek <john.r.van.drasek@intel.com>

src/otp538u/otp538u.h

@@ -0,0 +1,141 @@
+/*
+ * Author: Jon Trulson <jtrulson@ics.com>
+ * 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 <string>
+#include <mraa/aio.h>
+
+namespace upm {
+
+  /**
+   * @brief C++ API for the OTP538U IR Temperature Sensor
+   *
+   * UPM module for the OTP538U IR Temperature Sensor
+   *
+   * This module was tested with the Grove IR non-contact temperature
+   * sensor.
+   *
+   * The sensor provides 2 analog outputs - one for the thermistor
+   * that measures ambient temperature, and another for the thermopile
+   * that measures object temperature.
+   *
+   * Much of the code depends on analyzing the SeeedStudio examples
+   * and circuit design.  As a result, there are several 'magic'
+   * numbers that were derived from their circuit design.  By default,
+   * these values will be used.
+   *
+   * The tables used came from the datasheets "538U VT
+   * Table__20_200(v1.3).pdf" and "538RT_table.pdf".
+   *
+   * These tables assume the object to be measured is 9cm (3.54
+   * inches) from the sensor.
+   *
+   * @ingroup grove analog
+   * @defgroup otp538u libupm-otp538u
+   * @snippet otp538u.cxx Interesting
+   */
+  class OTP538U {
+  public:
+    /**
+     * OTP538U sensor constructor
+     *
+     * @param pinA analog pin to use for Ambient temperature
+     * @param pinO analog pin to use for Object temperature
+     * @param aref analog reference voltage, default 5.0
+     */
+    OTP538U(int pinA, int pinO, float aref = 5.0);
+
+    /**
+     * OTP538U Destructor
+     */
+    ~OTP538U();
+
+    /**
+     * Get the ambient temperature in C
+     *
+     * @return the ambient temperature
+     */
+    float ambientTemperature();
+
+    /**
+     * Get the object temperature in C
+     *
+     * @return the object's temperature
+     */
+    float objectTemperature();
+
+    /**
+     * Set the offset voltage
+     *
+     * The Seeedstudio wiki gives an example on calibrating the sensor
+     * and calculating the offset voltage to apply.  Currently, the
+     * default value is set, but you can use the function to set one
+     * of your own.
+     *
+     * @param vOffset the desired offset voltage
+     */
+    void setVoltageOffset(float vOffset) { m_offsetVoltage = vOffset; };
+
+    /**
+     * Set the output resistance value
+     *
+     * The Seeedstudio wiki example uses a value, 2000000 in one of
+     * the equations used to calculate a voltage.  The value is the
+     * resistance of a resistor they use in the output stage of their
+     * SIG2 output.  This was 'decoded' by looking at the eagle files
+     * containing their schematics for this device.
+     *
+     * @param outResistance value of output resistor, default 2M Ohm.
+     */
+    void setOutputResistence(int outResistance) { 
+      m_vResistance = outResistance; };
+
+    /**
+     * Set the voltage reference of the internal seedstudio voltage
+     * regulator on the sensor board.
+     *
+     * The Seeedstudio wiki example uses a value, 2.5 in one of the
+     * equations used to calculate the resistance of the ambient
+     * thermistor.  The value is the voltage of an internal voltage
+     * regulator used in the sensor board.  This was 'decoded' by
+     * looking at the eagle files containing their schematics for this
+     * device.
+     *
+     * @param vref internal sensor voltage reference, default 2.5
+     */
+    void setVRef(float vref) { m_vref = vref; };
+
+
+  private:
+    float m_vref;
+    float m_aref;
+    int m_vResistance;
+    float m_offsetVoltage;
+    int m_adcResolution;
+    mraa_aio_context m_aioA;
+    mraa_aio_context m_aioO;
+  };
+}
+
+