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 #ifdef DEBUG
   7
   8 #define UBRR_VAL ((F_CPU+BAUD*8)/(BAUD*16)-1)
   9 #define BAUD_REAL (F_CPU/(16*(UBRR_VAL+1)))
  10 #define BAUD_ERROR ((BAUD_REAL*1000)/BAUD)
  11
  12 #if ((BAUD_ERROR<990) || (BAUD_ERROR>1010))
  13 #error Systematischer Fehler der Baudrate grösser 1% und damit zu hoch!
  14 #endif
  15
  16 int usart_put(char c, FILE *stream)
  17 {
  18         if (c == '\n')
  19                 usart_put('\r', stream);
  20
  21         while(!(UCSRA & (1<<UDRE))) {}
  22         UDR = c;
  23         return 0;
  24 }
  25
  26 static FILE usart_stdout = FDEV_SETUP_STREAM(usart_put, NULL, _FDEV_SETUP_WRITE);
  27 #endif
  28
  29 void usart_init()
  30 {
  31 #ifdef DEBUG
  32         UCSRB |= (1<<TXEN);
  33         UCSRC |= (1<<URSEL)|(1 << UCSZ1)|(1 << UCSZ0);
  34
  35         UBRRH = UBRR_VAL >> 8;
  36         UBRRL = UBRR_VAL & 0xFF;
  37
  38         stdout = &usart_stdout;
  39 #endif
  40 }