upmc: Updates for building C modules w/base UPM

Test commit for building C UPM modules.

    * Added C include directory
    * Added C utilities directory
    * Rename C++ upm.h -> upm.hpp to make room for C upm.h
    * Added upm_mixed_module_init function to src/CMakeLists.txt.  This
      function takes filesnames similar to upm_module_init and does a
      bit of processing before calling upm_module_init.
    * Added c example directory.  Changed c++ example names.
    * Added dfrph implemention for testing (C++ wraps C).  Added mraa
      to .pc requires for dfrph.  Tested against stand-alone project.
      Added dfrph c example.
    * Update implemention of pkg-config file generation.
    * Added two cmake cache variables: BUILDCPP and BUILDFTI
    * Removed src from swig_add_module calls, added libname to
      swig_link_libraries calls.  Shrinks swig'ed binaries by ~13%.
    * Added install target in upm/CMakeLists.txt to install C header,
      directory.  Is this where we want this?
    * C FTI header directory is include/fti

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

src/dfrph/dfrph.cxx

@@ -23,52 +23,54 @@
  */
 
 #include <iostream>
+#include <stdexcept>
 
 #include "dfrph.hpp"
 
-using namespace std;
 using namespace upm;
 
-DFRPH::DFRPH(int pin, float aref) :
-  m_aio(pin)
+DFRPH::DFRPH(int pin, float vref) : _dev(dfrph_init(pin))
 {
-  m_aRes = (1 << m_aio.getBit());
-  m_aref = aref;
-
-  m_offset = 0.0;
+    if (_dev == NULL)
+        throw std::invalid_argument(std::string(__FUNCTION__) +
+                ": dfrph_init() failed, invalid pin?");
 }
 
 DFRPH::~DFRPH()
 {
-}
-
-float DFRPH::volts()
-{
-  int val = m_aio.read();
-
-  return(val * (m_aref / m_aRes));
+    dfrph_close(_dev);
 }
 
 void DFRPH::setOffset(float offset)
 {
-  m_offset = offset;
+    dfrph_set_offset(_dev, offset);
+}
+
+void DFRPH::setScale(float scale)
+{
+    dfrph_set_scale(_dev, scale);
+}
+
+float DFRPH::volts()
+{
+    float volts = 0.0;
+    dfrph_get_raw_volts(_dev, &volts);
+    return volts;
 }
 
 float DFRPH::pH(unsigned int samples)
 {
-  if (!samples)
-    samples = 1;
+    float ph_avg = 0.0;
 
-  float sum = 0.0;
+    // Read at least 1 sample
+    if (samples == 0) samples = 1;
 
-  for (int i=0; i<samples; i++)
+    float ph = 0.0;
+    for (int i =0; i < samples; i++)
     {
-      sum += volts();
-      usleep(20000);
+        dfrph_get_ph(_dev, &ph);
+        ph_avg += ph;
     }
 
-  sum /= samples;
-
-  // 3.5 is a 'magic' DFRobot number. Seems to work though :)
-  return (3.5 * sum + m_offset);
+    return ph_avg/samples;
 }