bh1750: Initial implementation

This driver was developed with the DFRobot Light Sensor based on the
BH1750.  It has a sensitivity of .5 to 65535 Lux.  It supports
voltages from 3-5vdc and is connected via I2C.

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

examples/c/CMakeLists.txt

@@ -89,3 +89,4 @@ link_directories (${MRAA_LIBDIR})
 add_example (dfrph)
 add_example (vk2828u7)
 add_example (mma7361)
+add_example (bh1750)

examples/c/bh1750.c

@@ -0,0 +1,75 @@
+/*
+ * 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 <signal.h>
+
+#include "bh1750.h"
+
+bool shouldRun = true;
+
+void sig_handler(int signo)
+{
+  if (signo == SIGINT)
+    shouldRun = false;
+}
+
+int main()
+{
+  signal(SIGINT, sig_handler);
+
+//! [Interesting]
+
+  // Instantiate a BH1750 sensor on default I2C bus (0), using the
+  // default I2C address (0x23), and setting the mode to highest
+  // resolution, lowest power mode.
+  bh1750_context sensor = bh1750_init(BH1750_DEFAULT_I2C_BUS,
+                                      BH1750_DEFAULT_I2C_ADDR,
+                                      BH1750_OPMODE_H2_ONCE);
+
+  if (!sensor)
+    {
+      printf("bh1750_init() failed.\n");
+      return 1;
+    }
+
+  // Every second, sample the BH1750 and output the measured lux value
+
+  while (shouldRun)
+    {
+      float lux;
+
+      bh1750_get_lux(sensor, &lux);
+      printf("Detected Light Level (lux): %f\n", lux);
+      sleep(1);
+    }
+
+//! [Interesting]
+
+  printf("Exiting\n");
+
+  bh1750_close(sensor);
+
+  return 0;
+}