#define UART_RX_FLAG_NICHT_KOMPLETT		0
#define UART_RX_FLAG_KOMPLETT			1
#define UART_BAUDRATE					9600UL
#define UART_TX_BUFFER_SIZE				50
#define UART_ZEICHEN_BUFFER_LEER		'§'
#define AN								1
#define AUS								0

unsigned char	UART_TX_Buffer[UART_TX_BUFFER_SIZE];
uint16_t		UART_TX_Buffer_Register_Senden, UART_TX_Buffer_Register_Schreiben;
uint8_t			UART_Flag_senden_aktiv;

void initUART(void)
{
	uint16_t cnt = 0;

	for(cnt=0;cnt<UART_TX_BUFFER_SIZE;cnt++)	UART_TX_Buffer[cnt] = UART_ZEICHEN_BUFFER_LEER;

	UART_TX_Buffer_Register_Senden		= 0;
	UART_TX_Buffer_Register_Schreiben	= 0;
	UART_Flag_senden_aktiv				= AUS;

	if(UART_BAUDRATE==115200UL)	UBRR0 = 8;
	else						UBRR0 = ( 16000000UL/(UART_BAUDRATE*16) )-1;
	UCSR0A = (0<<RXC0)	  | (0<<TXC0)    | (0<<UDRE0)  | (0<<FE0)   | (0<<DOR0)  | (0<<UPE0)   | (0<<U2X0)   | (0<<MPCM0);
	UCSR0C = (0<<UMSEL01) | (0<<UMSEL00) | (0<<UPM01)  | (0<<UPM00) | (0<<USBS0) | (1<<UCSZ01) | (1<<UCSZ00) | (0<<UCPOL0);
	UCSR0B = (0<<RXCIE0)  | (0<<TXCIE0)  | (0<<UDRIE0) | (0<<RXEN0) | (1<<TXEN0) | (0<<UCSZ02) | (0<<RXB80)  | (0<<TXB80);
}

void USART_UDRE_vect(void)
{
	if( !(UART_TX_Buffer[UART_TX_Buffer_Register_Senden]==UART_ZEICHEN_BUFFER_LEER) )
	{
		UDR0 = UART_TX_Buffer[UART_TX_Buffer_Register_Senden];
		UART_TX_Buffer[UART_TX_Buffer_Register_Senden] = UART_ZEICHEN_BUFFER_LEER;

		if( (UART_TX_Buffer_Register_Senden+1) < UART_TX_BUFFER_SIZE )
			UART_TX_Buffer_Register_Senden++;
		else
			UART_TX_Buffer_Register_Senden = 0;
	}
	// Alle Zeichen gesendet, ISR abschalten
	else
	{
		UART_Flag_senden_aktiv = AUS;
		UCSR0B &= ~(1<<UDRIE0);
	}
}

void UART_send(unsigned char data)
{
	UART_TX_Buffer[UART_TX_Buffer_Register_Schreiben] = data;

	if( (UART_TX_Buffer_Register_Schreiben+1) < UART_TX_BUFFER_SIZE )
		UART_TX_Buffer_Register_Schreiben++;
	else
		UART_TX_Buffer_Register_Schreiben = 0;

	// starten, wenn Buffer noch nicht bereits abgearbeitet wird
    if(UART_Flag_senden_aktiv==AUS)
    {
	    UART_Flag_senden_aktiv = AN;
		UCSR0B |= (1<<UDRIE0);
    }
}