#define F_CPU 8000000

#include <avr/io.h>
#include <stdlib.h>
#include <util/delay.h>

void I2Cinit(void)
{
	TWSR = 0;												//Kein Prescaler
	TWBR = 32;												//Macht ca. 100Hz
}

void I2Csend (int reg,int val)								// Single write
{
	TWCR = (1<<TWINT) | (1<<TWSTA) | (1<<TWEN);				// Sende START condition
	while(!(TWCR & (1<<TWINT)));							// wait until transmission completed
	if ((TWSR & 0xF8) != 0x08)								// Prescaler bits maskieren. Status code checken 0x08=START
	TWCR = (1<<TWINT)|(1<<TWEN)|(1<<TWSTO);					//
	
		TWDR = 0x52;										// Slave address ist 0x29
		TWCR = (1<<TWINT) | (1<<TWEN);						// 8-bit read is 0xC1, 8-bit write is 0xC0
		while(!(TWCR & (1<<TWINT)));						//
		if ((TWSR & 0xF8) != 0x18)							// 0x18=Schreiben+ACK
		TWCR = (1<<TWINT)|(1<<TWEN)|(1<<TWSTO);				//
	
			TWDR = reg;										// Übergebenes register in das geschrieben werden soll
			TWCR = (1<<TWINT) | (1<<TWEN);					// Senden
			while(!(TWCR & (1<<TWINT)));					//
			if ((TWSR & 0xF8) != 0x28)						// 0x28=Datenbyte übermittelt+ACK
			TWCR = (1<<TWINT)|(1<<TWEN)|(1<<TWSTO);			//
	
				TWDR = val;									// Übergebener Wert das geschrieben werden soll
				TWCR = (1<<TWINT) | (1<<TWEN);				//
				while(!(TWCR & (1<<TWINT)));				//
				if ((TWSR & 0xF8) != 0x28)					// 0x28=Datenbyte übermittelt+ACK
				TWCR = (1<<TWINT)|(1<<TWEN)|(1<<TWSTO);		//
	
	TWCR = (1<<TWINT)|(1<<TWEN)|(1<<TWSTO);					// STOP
	while(TWCR & (1<<TWSTO));								// wait until stop condition is executed and bus released
}

int I2Creceive (int reg)									// Single read
{
	TWCR = (1<<TWINT) | (1<<TWSTA) | (1<<TWEN);				// Sende START condition
	while(!(TWCR & (1<<TWINT)));							// wait until transmission completed
	if ((TWSR & 0xF8) != 0x08)								// Prescaler bits maskieren. Status code checken 0x08=START
	TWCR = (1<<TWINT)|(1<<TWEN)|(1<<TWSTO);
	
		TWDR = 0x52;										// Write (s.o.)
		TWCR = (1<<TWINT) | (1<<TWEN);						//
		while(!(TWCR & (1<<TWINT)));
		if ((TWSR & 0xF8) != 0x18)							// 0x18=Schreiben+ACK
		TWCR = (1<<TWINT)|(1<<TWEN)|(1<<TWSTO);				//
	
			TWDR = reg;										// Übergebenes Register aus dem gelesen werden soll
			TWCR = (1<<TWINT) | (1<<TWEN);					//
			while(!(TWCR & (1<<TWINT)));					//
			if ((TWSR & 0xF8) != 0x28)						// 0x28=Datenbyte übermittelt+ACK
			TWCR = (1<<TWINT)|(1<<TWEN)|(1<<TWSTO);			//
		
	TWCR = (1<<TWINT) | (1<<TWSTA) | (1<<TWEN);				// Repeated START condition
	while(!(TWCR & (1<<TWINT)));							//
	if ((TWSR & 0xF8) != 0x10)								// 0x10=repeated START
	TWCR = (1<<TWINT)|(1<<TWEN)|(1<<TWSTO);					//
	
		TWDR = 0x53;										// Read (s.o.)
		TWCR = (1<<TWINT) | (1<<TWEN);						//
		while(!(TWCR & (1<<TWINT)));						//
		if ((TWSR & 0xF8) != 0x40)							// 0x40=Lesen+ACK
		TWCR = (1<<TWINT)|(1<<TWEN)|(1<<TWSTO);				//
	
			TWCR = (1<<TWINT) | (1<<TWEN);					// Wert in TWDR einlesen.ACK senden
			while(!(TWCR & (1<<TWINT)));					//
			if ((TWSR & 0xF8) != 0x58)						// 0x58=Datenbyte erhalten kein ACK gesendet
			TWCR = (1<<TWINT)|(1<<TWEN)|(1<<TWSTO);			//
	
	TWCR = (1<<TWINT)|(1<<TWEN)|(1<<TWSTO);					// STOP
	while(TWCR & (1<<TWSTO));								// wait until stop condition is executed and bus released
	
	return TWDR;											// Ausgelesenen Wert zurückgeben 
}


int main(void){
	
	int i = 0;
	char test[7];
	
	lcdinit();
	I2Cinit();
	
	string("XYZ");
	
	
	
	while (1)
	{
		I2Csend(0x00,0xA0);
		i = I2Creceive(0x12);

		itoa(i,test,10);
		string(test);
		_delay_ms(100);
		cleardisplay();
	}
	
}