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fixed the USART

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This commit is contained in:
Daniel Knüttel 2019-01-17 19:39:05 +01:00
parent ac04dfc73f
commit ac2d26bd65
1 changed files with 18 additions and 7 deletions
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25
usart.c
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@ -3,6 +3,7 @@
#include "usart.h"
#include "conf.h"
#include "ringbuffer.h"
#include <avr/interrupt.h>
volatile ringbuffer_t usart_buffer;
@ -11,16 +12,26 @@ void
usart_init(void)
{
usart_buffer = ringbuffer_new(USART_BUFFER_SIZE);
UBRRH = (unsigned char)(UBRR_VALUE >> 8);
UBRRL = (unsigned char)UBRR_VALUE;
UCSRB = _BV(TXEN) | _BV(TXCIE);
UCSRC = _BV(USBS) | _BV(UCSZ0) | _BV(UCSZ1);
UBRR0H = (unsigned char)(UBRR_VALUE >> 8);
UBRR0L = (unsigned char)UBRR_VALUE;
UCSR0B = _BV(TXEN0) | _BV(TXCIE0);
UCSR0C = _BV(UCSZ00) | _BV(UCSZ01);
sei();
}
int
usart_putc(char c)
{
return ringbuffer_put_char(usart_buffer, c);
int result = ringbuffer_put_char(usart_buffer, c);
// If the buffer is already emtpy there is no
// need to wait for the interrupt.
// Also it is likely that the interrupt will never happen.
// (For instance because this is the first byte sent)
if(UCSR0A & _BV(UDRE0))
{
UDR0 = ringbuffer_get_char(usart_buffer);
}
return result;
}
@ -29,7 +40,7 @@ ISR(USART_TX_vect)
{
if(ringbuffer_nonempty(usart_buffer))
{
while(!(UCSRA & UDRE));
UDR = ringbuffer_get_char(usart_buffer);
UDR0 = ringbuffer_get_char(usart_buffer);
UCSR0A |= _BV(TXC0);
}
}