examples: C/C++ examples use transitive dependencies

Updated the examples to comprehend transitive dependencies.  This means
that each example target will no longer have a giant list of -I includes
(the examples at the end of the list had includes for all previous
examples, upwards of 200 -I's on the command line).

    * Created a CMakeLists.txt in the upm/examples directory, moved
      common functionality to this level.
    * C/C++ examples now look to the filename for their dependency
      target name, ie; gas-mq2.cxx adds a dependency to the 'gas' target
    * Updated a handful of C/C++ example names to reflect this
    * Example CMake flow - glob the list of files, add targets for any
      special case examples, then att targets for all the rest

Signed-off-by: Noel Eck <noel.eck@intel.com>

examples/c++/ads1x15-ads1115.cxx

@@ -0,0 +1,105 @@
+/*
+ * Author: Mihai Tudor Panu <mihai.tudor.panu@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.
+ */
+
+/* This example demonstrates how to use one of the ADS1115 ADCs on the
+ * DFRobot Joule Shield with devices that output a small differential
+ * voltage (e.g. geophones, piezoelectric bands or pads, thermocouples).
+ */
+
+#include <fstream>
+#include <string>
+#include <thread>
+#include <unistd.h>
+
+#include "ads1115.hpp"
+
+using namespace std;
+using namespace upm;
+
+bool running = true; // Controls main read/write loop
+
+// Thread function
+void stop()
+{
+    sleep(10);
+    running = false;
+}
+
+int main()
+{
+    long id = 0; // Sample number
+    string fileName = "./ads1115.data"; // Output filename
+    ofstream f;
+
+    // Initialize and configure the ADS1115 for the SM-24 Geophone
+    // There are two ADS1115 chips on the DFRobot Joule Shield on the same I2C bus
+    //     - 0x48 gives access to pins A0 - A3
+    //     - 0x49 gives access to pins A4 - A7
+    ADS1115 *ads1115 = new upm::ADS1115(0, 0x48);
+
+    // Put the ADC into differential mode for pins A0 and A1,
+    // the SM-24 Geophone is connected to these pins
+    ads1115->getSample(ADS1X15::DIFF_0_1);
+
+    // Set the gain based on expected VIN range to -/+ 2.048 V
+    // Can be adjusted based on application to as low as -/+ 0.256 V, see API
+    // documentation for details
+    ads1115->setGain(ADS1X15::GAIN_TWO);
+
+    // Set the sample rate to 860 samples per second (max) and turn on continuous
+    // sampling
+    ads1115->setSPS(ADS1115::SPS_860);
+    ads1115->setContinuous(true);
+
+    // Enable exceptions from the output stream
+    f.exceptions(ofstream::failbit | ofstream::badbit);
+    // Open the file
+    try{
+        f.open(fileName);
+
+        // Output formatting
+        f.setf(ios_base::fixed);
+        f.precision(7);
+
+        // Start the thread that will stop logging after 10 seconds
+        thread timer (stop);
+
+        // Read sensor data and write it to the output file every ms
+        while(running){
+            f << id++ << " " << ads1115->getLastSample() << endl;
+            usleep(1000);
+        }
+
+        // Clean-up and exit
+        timer.join();
+        f.close();
+        delete ads1115;
+    } catch (ios_base::failure &e) {
+        cout << "Failed to write to file: " << e.what() << endl;
+        return 1;
+    }
+    cout << "Wrote " << id << " samples to file: " << fileName << endl;
+    return 0;
+}
+