configurable i2c bitrate on arduino nano

src/app/i2cbench/main.cc

@@ -25,8 +25,9 @@
 void loop(void)
 {
 #ifdef DRIVER_LM75
-	kout.printf_float(lm75.getTemp());
-	kout << endl;
+	//kout.printf_float(lm75.getTemp());
+	//kout << endl;
+	lm75.setOS(64);
 #endif
 #ifdef DRIVER_AM2320
 	am2320.read();

src/arch/arduino-nano/Makefile.inc

@@ -32,6 +32,10 @@ ifneq ($(findstring stdin,${arch_drivers}), )
 	TARGETS += src/arch/arduino-nano/driver/stdin.cc
 endif
 
+ifneq (${i2c_freq}, )
+	COMMON_FLAGS += -DF_I2C=${i2c_freq}
+endif
+
 OBJECTS = ${TARGETS:.cc=.o}
 
 .cc.o:

src/arch/arduino-nano/driver/i2c.cc

@@ -3,6 +3,10 @@
 #include <avr/io.h>
 #include <avr/interrupt.h>
 
+#ifndef F_I2C
+#define F_I2C 100000UL
+#endif
+
 inline void await_twint(unsigned char twcr_values)
 {
 	TWCR = twcr_values | _BV(TWINT) | _BV(TWIE);
@@ -99,7 +103,7 @@ static signed char i2c_receive(uint8_t len, uint8_t *data)
 signed char I2C::setup()
 {
 	TWSR = 0;
-	TWBR = ((F_CPU / 100000UL) - 16) / 2;
+	TWBR = ((F_CPU / F_I2C) - 16) / 2;
 
 	return 0;
 }