Probleme ATmega164P + PCA9554

#define ADDRESS 0x20

void Init_TWI (void)

{

  TWBR = 72; //set Bus speed 100kHz @16Mhz MCKL

}

void TWI_send_start (void)

{

  TWCR = (1<<TWINT) | (1<<TWSTA) | (1<<TWEN); //Send START condition

  while (!(TWCR & (1<<TWINT))); //Wait for TWINT Flag set.

}

void TWI_send_add_rw (unsigned char address, unsigned char rw)

{

  unsigned char addr_byte = 0;

  addr_byte = address << 1; //shift address one bit left

  addr_byte |= rw; //set RW-Bit, if necessary

  TWDR = addr_byte;

  TWCR = (1<<TWINT) | (1<<TWEN); //send content of TWDR

    while (!(TWCR & (1<<TWINT))); //wait, until address has been sent

}

unsigned char TWI_read_byte (void)

{

  TWCR = (1<<TWINT) | (1<<TWEA) | (1<<TWEN);

    while (!(TWCR & (1<<TWINT))); //wait, until byte has been received

  return TWDR;

}

void TWI_send_byte (unsigned char byte)

{

  TWDR = byte;

  TWCR = (1<<TWINT) | (1<<TWEN); //send content of TWDR

    while (!(TWCR & (1<<TWINT))); //wait, until byte has been sent

}

void TWI_send_stop (void)

{

  TWCR = (1<<TWINT) | (1<<TWSTO) | (1<<TWEN);  

  delay_ms(1); //wait a bit

}

int main(void) {

  Init_TWI();

while (1) {

  TWI_send_start ();

  TWI_send_add_rw (ADDRESS, 0);

  TWI_send_byte (0x1);

  TWI_send_byte (0x0);

  TWI_send_stop ();

  USART_transmit(input);

  delay_ms(2000);

}  //while

} //main