uint8_t twi_start(uint8_t twi_address, uint8_t r_w) 
{	
	TWCR = (1<<TWINT) | (1<<TWSTA) | (1<<TWEN); 		
	while (!(TWCR & (1<<TWINT)));
			
	if ((TWSR & 0xF8) != TW_START) 
	{
		return 1;
	} 
		
	TWDR = ((twi_address << 1) | r_w); 
	TWCR = (1<<TWINT) | (1<<TWEN); 
	
	while (!(TWCR & (1<<TWINT))); 
				
	uint8_t STATUS_CODE = (TWSR & 0xF8);
	if ((STATUS_CODE != TW_MT_SLA_ACK) && (STATUS_CODE!= TW_MR_SLA_ACK)) 
	{
		return 1; 
	}	
	else return 0; 
}