Implemented setClock for the Due as well

This allows users to change the I2C clock frequency

Author: Lauszus

hardware/arduino/sam/libraries/Wire/Wire.cpp

@@ -96,7 +96,7 @@ TwoWire::TwoWire(Twi *_twi, void(*_beginCb)(void)) :
 	twi(_twi), rxBufferIndex(0), rxBufferLength(0), txAddress(0),
 			txBufferLength(0), srvBufferIndex(0), srvBufferLength(0), status(
 					UNINITIALIZED), onBeginCallback(_beginCb) {
-	// Empty
+	setClock(100000); // Set clock frequency to 100000 Hz
 }
 
 void TwoWire::begin(void) {
@@ -106,7 +106,7 @@ void TwoWire::begin(void) {
 	// Disable PDC channel
 	twi->TWI_PTCR = UART_PTCR_RXTDIS | UART_PTCR_TXTDIS;
 
-	TWI_ConfigureMaster(twi, TWI_CLOCK, VARIANT_MCK);
+	TWI_ConfigureMaster(twi, twiClock, VARIANT_MCK);
 	status = MASTER_IDLE;
 }
 
@@ -127,6 +127,10 @@ void TwoWire::begin(int address) {
 	begin((uint8_t) address);
 }
 
+void TwoWire::setClock(uint32_t frequency) {
+	twiClock = frequency;
+}
+
 uint8_t TwoWire::requestFrom(uint8_t address, uint8_t quantity, uint8_t sendStop) {
 	if (quantity > BUFFER_LENGTH)
 		quantity = BUFFER_LENGTH;

hardware/arduino/sam/libraries/Wire/Wire.h

@@ -35,6 +35,7 @@ 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);
@@ -99,7 +100,7 @@ class TwoWire : public Stream {
 	TwoWireStatus status;
 
 	// TWI clock frequency
-	static const uint32_t TWI_CLOCK = 100000;
+	uint32_t twiClock;
 
 	// Timeouts (
 	static const uint32_t RECV_TIMEOUT = 100000;

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

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