git.zerfleddert.de Git - rsbs2/blob - bmc/usart.c

   1 #include <avr/io.h>
   2 #include <stdio.h>
   3
   4 #include "usart.h"
   5
   6 #define UBRR_VAL ((F_CPU+BAUD*8)/(BAUD*16)-1)
   7 #define BAUD_REAL (F_CPU/(16*(UBRR_VAL+1)))
   8 #define BAUD_ERROR ((BAUD_REAL*1000)/BAUD)
   9
  10 #if ((BAUD_ERROR<990) || (BAUD_ERROR>1010))
  11 #error Systematischer Fehler der Baudrate grösser 1% und damit zu hoch!
  12 #endif
  13
  14 int usart_put(char c, FILE *stream)
  15 {
  16         if (c == '\n')
  17                 usart_put('\r', stream);
  18
  19         while(!(UCSRA & (1<<UDRE))) {}
  20         UDR = c;
  21         return 0;
  22 }
  23
  24 static FILE usart_stdout = FDEV_SETUP_STREAM(usart_put, NULL, _FDEV_SETUP_WRITE);
  25
  26 void usart_init()
  27 {
  28         UCSRB |= (1<<TXEN);
  29         UCSRC |= (1<<URSEL)|(1 << UCSZ1)|(1 << UCSZ0);
  30
  31         UBRRH = UBRR_VAL >> 8;
  32         UBRRL = UBRR_VAL & 0xFF;
  33
  34         stdout = &usart_stdout;
  35 }