dfrec: Initial implementation

This module implements support for the DFRobot EC (Electrical
Conductivity) meter.  It relies on the use of the DS18B20 UPM C module
for temperature gathering.

It has a pretty complicated calibration procedure which is somewhat
documented on the DFRobot wiki.  Functions have been added to support
changing the various coefficients as desired.

Signed-off-by: Jon Trulson <jtrulson@ics.com>

src/dfrec/dfrec.cxx

@@ -0,0 +1,108 @@
+/*
+ * Author: Jon Trulson <jtrulson@ics.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.
+ */
+
+#include <iostream>
+#include <stdexcept>
+
+#include "dfrec.hpp"
+
+using namespace upm;
+using namespace std;
+
+DFREC::DFREC(unsigned int apin, unsigned int uart_ow,
+             unsigned int device_idx,
+             float a_ref) :
+  m_dfrec(dfrec_init(apin, uart_ow, device_idx, a_ref))
+{
+  if (!m_dfrec)
+    throw std::runtime_error(string(__FUNCTION__)
+                             + ": dfrec_init() failed");
+}
+
+DFREC::~DFREC()
+{
+  dfrec_close(m_dfrec);
+}
+void DFREC::update()
+{
+  upm_result_t rv = dfrec_update(m_dfrec);
+
+  // we only want to throw on "real" fatal errors
+  if (!(rv == UPM_ERROR_OUT_OF_RANGE || rv == UPM_SUCCESS))
+    {
+      throw std::runtime_error(string(__FUNCTION__)
+                               + ": dfrec_update() failed with UPM error "
+                               + std::to_string(int(rv)) );
+    }
+}
+
+void DFREC::setOffset(float offset)
+{
+  dfrec_set_offset(m_dfrec, offset);
+}
+
+void DFREC::setScale(float scale)
+{
+  dfrec_set_scale(m_dfrec, scale);
+}
+
+float DFREC::getEC()
+{
+  return dfrec_get_ec(m_dfrec);
+}
+
+float DFREC::getVolts()
+{
+  return dfrec_get_volts(m_dfrec);
+}
+
+float DFREC::getNormalized()
+{
+  return dfrec_get_normalized(m_dfrec);
+}
+
+float DFREC::getTemperature()
+{
+  return dfrec_get_temperature(m_dfrec);
+}
+
+void DFREC::setThresholdMinMax(float min, float max)
+{
+  dfrec_set_threshold_min_max(m_dfrec, min, max);
+}
+
+void DFREC::setThreshold1(float thres, float scale, float offset)
+{
+  dfrec_set_threshold_1(m_dfrec, thres, scale, offset);
+}
+
+void DFREC::setThreshold2(float thres, float scale, float offset)
+{
+  dfrec_set_threshold_2(m_dfrec, thres, scale, offset);
+}
+
+void DFREC::setThreshold3(float scale, float offset)
+{
+  dfrec_set_threshold_3(m_dfrec, scale, offset);
+}