Merge pull request #1912 from Lauszus/issues440

Enable user to change the I2C clock frequency by calling setClock in the Wire library

Author: cmaglie

hardware/arduino/avr/libraries/Wire/Wire.cpp

@@ -75,6 +75,11 @@ void TwoWire::begin(int address)
   begin((uint8_t)address);
 }
 
+void TwoWire::setClock(uint32_t frequency)
+{
+  TWBR = ((F_CPU / frequency) - 16) / 2;
+}
+
 uint8_t TwoWire::requestFrom(uint8_t address, uint8_t quantity, uint8_t sendStop)
 {
   // clamp to buffer length

hardware/arduino/avr/libraries/Wire/Wire.h

@@ -49,6 +49,7 @@ class TwoWire : public Stream
     void begin();
     void begin(uint8_t);
     void begin(int);
+    void setClock(uint32_t);
     void beginTransmission(uint8_t);
     void beginTransmission(int);
     uint8_t endTransmission(void);
@@ -62,10 +63,10 @@ class TwoWire : public Stream
     virtual int available(void);
     virtual int read(void);
     virtual int peek(void);
-	virtual void flush(void);
+    virtual void flush(void);
     void onReceive( void (*)(int) );
     void onRequest( void (*)(void) );
-  
+
     inline size_t write(unsigned long n) { return write((uint8_t)n); }
     inline size_t write(long n) { return write((uint8_t)n); }
     inline size_t write(unsigned int n) { return write((uint8_t)n); }

hardware/arduino/avr/libraries/Wire/keywords.txt

@@ -11,6 +11,7 @@
 #######################################
 
 begin	KEYWORD2
+setClock	KEYWORD2
 beginTransmission	KEYWORD2
 endTransmission	KEYWORD2
 requestFrom	KEYWORD2