diff --git a/firmware/Makefile b/firmware/Makefile
index 875c3a4..af8b59d 100644
--- a/firmware/Makefile
+++ b/firmware/Makefile
@@ -13,21 +13,29 @@ all:	master slave
 master:
 	cd masterchip; $(MAKE) $(MFLAGS)
 
+clean-master:
+	cd masterchip; $(MAKE) $(MFLAGS) clean
+
 flash-master:
 	cd masterchip; $(MAKE) $(MFLAGS) flash
 
 fuses-master:
 	cd masterchip; $(MAKE) $(MFLAGS) fuses
 
+
 slave:
 	cd slavechip; $(MAKE) $(MFLAGS)
 
+clean-slave:
+	cd slavechip; $(MAKE) $(MFLAGS) clean
+
 flash-slave:
 	cd slavechip; $(MAKE) $(MFLAGS) flash
 
 fuses-slave:
 	cd slavechip; $(MAKE) $(MFLAGS) fuses
 
+
 clean:
 	cd masterchip; $(MAKE) $(MFLAGS) clean
 	cd slavechip; $(MAKE) $(MFLAGS) clean
diff --git a/firmware/slavechip/i2c_simple.c b/firmware/slavechip/i2c_simple.c
index f946064..1965d49 100644
--- a/firmware/slavechip/i2c_simple.c
+++ b/firmware/slavechip/i2c_simple.c
@@ -1,23 +1,97 @@
-
 #include <stdint.h>
 
 #include "i2c_simple.h"
 
-
-
-void i2c_init(){
-    //TODO: implement
+void i2c_init()
+{
+	TWBR = 0;//bit rate
+	TWSR = 0;//Prescaler
+	
+	TWAR = 0x80;//our address 1000 000, don't listen to general call
+	TWAMR = 0;
+	
+	TWCR = TWEA | TWEN;/* TWINT clear -> we must do something; unset TWSTA manually!, TWSTO */
+	//TWDR - data
 }
 
-uint8_t i2c_read(uint8_t addr, uint8_t len, uint8_t *data){
-    return 0; //TODO: implement
+uint8_t i2c_read(uint8_t addr, uint8_t len, uint8_t *data)
+{
+	TWCR &= ~TWSTO;
+	TWCR |= TWINT | TWSTA;
+	while(~TWCR & TWINT) {;}/* get bus access */
+	/* no error possible */
+	
+	TWDR = addr | 1;
+	TWCR &= ~(TWSTA | TWSTO);
+	TWCR |= TWINT;
+	while(~TWCR & TWINT) {;}/* transmit address */
+	/* possible results: ACK, NAK, abitration lost */
+	if(TW_STATUS == TW_MR_SLA_NACK)
+	{
+		TWCR |= TWINT | TWSTO;
+		return 0;
+	}
+	else if(TW_STATUS == TW_MR_ARB_LOST) {return 0;}
+	
+	uint8_t done = 0;
+	while(done + 1 < len)
+	{
+		TWCR |= TWEA | TWINT;/* send ack after byte */
+		while(~TWCR & TWINT) {;}/* read data */
+		data[done] = TWDR;
+		done++;
+		TWCR |= TWINT;
+	}
+	
+	TWCR &= ~TWEA;
+	TWCR |= TWINT;/* send nak after byte */
+	while(~TWCR & TWINT) {;}/* read data */
+	data[done] = TWDR;
+	done++;
+	TWCR |= TWINT | TWSTO;
+	return done;
 }
 
-uint8_t i2c_write(uint8_t addr, uint8_t len, uint8_t *data){
-    return 0; //TODO: implement
+uint8_t i2c_write(uint8_t addr, uint8_t len, uint8_t *data)
+{
+	TWCR &= ~TWSTO;
+	TWCR |= TWINT | TWSTA;
+	while(~TWCR & TWINT) {;}/* get bus access */
+	/* no error possible */
+	
+	TWDR = addr;
+	TWCR &= ~(TWSTA | TWSTO);
+	TWCR |= TWINT;
+	while(~TWCR & TWINT) {;}/* transmit address */
+	/* possible results: ACK, NAK, abitration lost */
+	if(TW_STATUS == TW_MT_SLA_NACK)
+	{
+		TWCR |= TWINT | TWSTO;
+		return 0;
+	}
+	else if(TW_STATUS == TW_MT_ARB_LOST) {return 0;}
+	
+	uint8_t done = 0;
+	while(done < len)
+	{
+		TWDR = data[done];
+		TWCR |= TWINT;
+		while(~TWCR & TWINT) {;}/* write data */
+		/* possible results: ACK, NAK, abitration lost */
+		if(TW_STATUS == TW_MT_DATA_NACK)
+		{
+			TWCR |= TWINT | TWSTO;
+			return done;
+		}
+		else if(TW_STATUS == TW_MT_ARB_LOST) {return done;}
+		done++;
+	}
+	
+	TWCR |= TWINT | TWSTO;
+	return done;
 }
 
-uint8_t i2c_write_read(uint8_t addr, uint8_t writelen, uint8_t* writedata, uint8_t readlen, 
-        uint8_t* readdata){
-    return 0; //TODO: implement
+uint8_t i2c_write_read(uint8_t addr, uint8_t writelen, uint8_t *writedata, uint8_t readlen, uint8_t *readdata)
+{
+	return 0; //TODO: implement
 }
diff --git a/firmware/slavechip/i2c_simple.h b/firmware/slavechip/i2c_simple.h
index c7aee5f..2e76444 100644
--- a/firmware/slavechip/i2c_simple.h
+++ b/firmware/slavechip/i2c_simple.h
@@ -1,7 +1,5 @@
-
-
-
-
+#ifndef I2C_SIMPLE_H
+#define I2C_SIMPLE_H
 
 /* initializes i2c interface (master, 400kHz) */
 void i2c_init();
@@ -13,5 +11,6 @@ uint8_t i2c_read(uint8_t addr, uint8_t len, uint8_t *data);
 uint8_t i2c_write(uint8_t addr, uint8_t len, uint8_t *data);
 
 /* writes, followed by a repeated start and a read */
-uint8_t i2c_write_read(uint8_t addr, uint8_t writelen, uint8_t* writedata, uint8_t readlen, 
-        uint8_t* readdata);
+uint8_t i2c_write_read(uint8_t addr, uint8_t writelen, uint8_t *writedata, uint8_t readlen, uint8_t *readdata);
+
+#endif