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>

examples/c++/CMakeLists.txt

@@ -278,6 +278,7 @@ add_example (mma7361)
 add_example (bh1750)
 add_example (hka5)
 add_example (dfrorp)
+add_example (dfrec)
 
 # These are special cases where you specify example binary, source file and module(s)
 include_directories (${PROJECT_SOURCE_DIR}/src)

examples/c++/dfrec.cxx

@@ -0,0 +1,81 @@
+/*
+ * 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 <unistd.h>
+#include <iostream>
+#include <signal.h>
+
+#include "dfrec.hpp"
+
+using namespace std;
+
+bool shouldRun = true;
+
+void sig_handler(int signo)
+{
+  if (signo == SIGINT)
+    shouldRun = false;
+}
+
+int main()
+{
+  signal(SIGINT, sig_handler);
+
+//! [Interesting]
+
+  // Instantiate a DFRobot EC sensor on analog pin A0, with a ds18b20
+  // temperature sensor connected to UART 0, and a device index (for
+  // the ds1820b uart bus) of 0, and an analog reference voltage of
+  // 5.0.
+  upm::DFREC *sensor = new upm::DFREC(0, 0, 0, 5.0);
+
+  // Every 2 seconds, update and print values
+  while (shouldRun)
+    {
+      sensor->update();
+
+      cout << "EC = "
+           << sensor->getEC()
+           << " ms/cm"
+           << endl;
+
+      cout << "Volts = "
+           << sensor->getVolts()
+           << ", Temperature = "
+           << sensor->getTemperature()
+           << " C"
+           << endl;
+
+      cout << endl;
+
+      sleep(2);
+    }
+
+//! [Interesting]
+
+  cout << "Exiting" << endl;
+
+  delete sensor;
+  return 0;
+}