Merge pull request #15 from coelner/i2cPins

All free selection of I2c pins on ESP8266. This resolves #13.

BH1750.cpp

@@ -56,6 +56,20 @@ BH1750::BH1750(byte addr) {
 
 }
 
+/**
+ * Begin I2C and configure sensor
+ * @param SDA Date SCL Clock mode Measurment mode
+ */
+#if defined(ARDUINO_ARCH_ESP8266)
+void BH1750::begin(uint8_t SDA, uint8_t SCL, uint8_t mode) {
+
+  // allow config of pins
+  Wire.begin(SDA,SCL);
+
+  // Configure sensor in specified mode
+  configure(mode);
+}
+#endif
 
 /**
  * Begin I2C and configure sensor

BH1750.h

@@ -60,6 +60,10 @@ class BH1750 {
 
   public:
     BH1750 (byte addr = 0x23);
+    #if defined(ARDUINO_ARCH_ESP8266)
+    /* ==== On esp8266 it is possible to define I2C pins ==== */
+    void begin (uint8_t SDA, uint8_t SCL, uint8_t mode = BH1750_CONTINUOUS_HIGH_RES_MODE);
+    #endif
     void begin (uint8_t mode = BH1750_CONTINUOUS_HIGH_RES_MODE);
     void configure (uint8_t mode);
     uint16_t readLightLevel(void);

examples/BH1750test/BH1750test.ino

@@ -9,8 +9,8 @@
 
     VCC -> 5V (3V3 on Arduino Due, Zero, MKR1000, etc)
     GND -> GND
-    SCL -> SCL (A5 on Arduino Uno, Leonardo, etc or 21 on Mega and Due)
-    SDA -> SDA (A4 on Arduino Uno, Leonardo, etc or 20 on Mega and Due)
+    SCL -> SCL (A5 on Arduino Uno, Leonardo, etc or 21 on Mega and Due on esp8266 free selectable)
+    SDA -> SDA (A4 on Arduino Uno, Leonardo, etc or 20 on Mega and Due on esp8266 free selectable)
     ADD -> (not connected) or GND
 
   ADD pin uses to set sensor I2C address. If it has voltage greater or equal to
@@ -29,6 +29,7 @@ void setup(){
 
   Serial.begin(9600);
   lightMeter.begin();
+  //lightMeter.begin(begin(D4, D3)); //use this line on a esp8266
   Serial.println(F("BH1750 Test"));
 
 }