Update i2c.h

add timeout and errorcodes

i2c.h

@@ -10,13 +10,23 @@
 #define i2c_h
 
 /* TODO: setup i2c/twi */
-#define F_I2C			400000UL// clock i2c
+#define F_I2C			100000UL// clock i2c
 #define PSC_I2C			1		// prescaler i2c
 #define SET_TWBR		(F_CPU/F_I2C-16UL)/(PSC_I2C*2UL)
 
 #include <stdio.h>
 #include <avr/io.h>
 
+extern uint8_t I2C_ErrorCode;		// variable for communication error at twi
+									// ckeck it in your code
+									// 0 means no error
+									// define bits in I2C-ErrorCode:
+#define I2C_START		0			// bit 0: timeout start-condition
+#define I2C_SENDADRESS	1			// bit 0: timeout device-adress
+#define I2C_BYTE		2			// bit 0: timeout byte-transmission
+#define I2C_READACK		3			// bit 0: timeout read acknowledge
+#define I2C_READNACK	4			// bit 0: timeout read nacknowledge
+
 void i2c_init(void);				// init hw-i2c
 void i2c_start(uint8_t i2c_addr);	// send i2c_start_condition
 void i2c_stop(void);				// send i2c_stop_condition