add BH1750 sensor example

examples/osd/arduino-bh1750/sketch.pde

@@ -0,0 +1,49 @@
+/*
+ * Sample arduino sketch using contiki features.
+ * We turn the LED off 
+ * We allow read the moisture sensor
+ * Unfortunately sleeping for long times in loop() isn't currently
+ * possible, something turns off the CPU (including PWM outputs) if a
+ * Proto-Thread is taking too long. We need to find out how to sleep in
+ * a Contiki-compatible way.
+ * Note that for a normal arduino sketch you won't have to include any
+ * of the contiki-specific files here, the sketch should just work.
+ */
+
+#include <Wire.h>
+#include "BH1750FVI.h"
+
+extern "C" {
+#include "arduino-process.h"
+#include "rest-engine.h"
+
+BH1750FVI lightMeter;
+
+extern resource_t res_bh1750, res_battery;
+uint16_t lux;
+
+#define LED_PIN 4
+}
+
+void setup (void)
+{
+    // switch off the led
+    pinMode(LED_PIN, OUTPUT);
+    digitalWrite(LED_PIN, HIGH);
+    // BH1750 sensor
+    lightMeter.begin();
+    // init coap resourcen
+    rest_init_engine ();
+    rest_activate_resource (&res_bh1750, "s/lux");
+    rest_activate_resource (&res_battery, "s/battery");
+}
+
+// at project-conf.h
+// LOOP_INTERVAL		(10 * CLOCK_SECOND)
+void loop (void)
+{
+	mcu_sleep_off();
+    lux = lightMeter.getLightLevel();
+  	mcu_sleep_on();    
+	printf("Lux: %d",lux);
+}