+#include <avr/io.h>
+#include <stdio.h>
+
+#include "usart.h"
+
+#define UBRR_VAL ((F_CPU+BAUD*8)/(BAUD*16)-1)
+#define BAUD_REAL (F_CPU/(16*(UBRR_VAL+1)))
+#define BAUD_ERROR ((BAUD_REAL*1000)/BAUD)
+
+#if ((BAUD_ERROR<990) || (BAUD_ERROR>1010))
+#error Systematischer Fehler der Baudrate grösser 1% und damit zu hoch!
+#endif
+
+int usart_put(char c, FILE *stream)
+{
+ if (c == '\n')
+ usart_put('\r', stream);
+
+ while(!(UCSRA & (1<<UDRE))) {}
+ UDR = c;
+ return 0;
+}
+
+static FILE usart_stdout = FDEV_SETUP_STREAM(usart_put, NULL, _FDEV_SETUP_WRITE);
+
+void usart_init()
+{
+ UCSRB |= (1<<TXEN);
+ UCSRC |= (1<<URSEL)|(1 << UCSZ1)|(1 << UCSZ0);
+
+ UBRRH = UBRR_VAL >> 8;
+ UBRRL = UBRR_VAL & 0xFF;
+
+ stdout = &usart_stdout;
+}