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/*
* ----------------------------------------------------------------------------
* "THE BEER-WARE LICENSE" (Revision 42):
* <joerg@FreeBSD.ORG> wrote this file. As long as you retain this notice you
* can do whatever you want with this stuff. If we meet some day, and you think
* this stuff is worth it, you can buy me a beer in return. Joerg Wunsch
* ----------------------------------------------------------------------------
*
* Stdio demo, UART implementation
*
* $Id: uart.c,v 1.1 2005/12/28 21:38:59 joerg_wunsch Exp $
*/
#include "defines.h"
#include <stdint.h>
#include <stdio.h>
#include <avr/io.h>
#include "uart.h"
/*
* Initialize the UART to 9600 Bd, tx/rx, 8N1.
*/
void
uart_init(void)
{
#if F_CPU < 2000000UL && defined(U2X)
UCSRA = _BV(U2X); /* improve baud rate error by using 2x clk */
UBRRL = (F_CPU / (8UL * UART_BAUD)) - 1;
#else
UBRRL = (F_CPU / (16UL * UART_BAUD)) - 1;
#endif
UCSRB = _BV(TXEN) | _BV(RXEN); /* tx/rx enable */
}
/*
* Send character c down the UART Tx, wait until tx holding register
* is empty.
*/
int
uart_putchar(char c, FILE *stream)
{
if (c == '\a')
{
fputs("*ring*\n", stderr);
return 0;
}
if (c == '\n')
uart_putchar('\r', stream);
loop_until_bit_is_set(UCSRA, UDRE);
UDR = c;
return 0;
}
/*
* Receive a character from the UART Rx.
*
* This features a simple line-editor that allows to delete and
* re-edit the characters entered, until either CR or NL is entered.
* Printable characters entered will be echoed using uart_putchar().
*
* Editing characters:
*
* . \b (BS) or \177 (DEL) delete the previous character
* . ^u kills the entire input buffer
* . ^w deletes the previous word
* . ^r sends a CR, and then reprints the buffer
* . \t will be replaced by a single space
*
* All other control characters will be ignored.
*
* The internal line buffer is RX_BUFSIZE (80) characters long, which
* includes the terminating \n (but no terminating \0). If the buffer
* is full (i. e., at RX_BUFSIZE-1 characters in order to keep space for
* the trailing \n), any further input attempts will send a \a to
* uart_putchar() (BEL character), although line editing is still
* allowed.
*
* Input errors while talking to the UART will cause an immediate
* return of -1 (error indication). Notably, this will be caused by a
* framing error (e. g. serial line "break" condition), by an input
* overrun, and by a parity error (if parity was enabled and automatic
* parity recognition is supported by hardware).
*
* Successive calls to uart_getchar() will be satisfied from the
* internal buffer until that buffer is emptied again.
*/
int
uart_getchar(FILE *stream)
{
uint8_t c;
char *cp, *cp2;
static char b[RX_BUFSIZE];
static char *rxp;
if (rxp == 0)
for (cp = b;;)
{
loop_until_bit_is_set(UCSRA, RXC);
if (UCSRA & _BV(FE))
return _FDEV_EOF;
if (UCSRA & _BV(DOR))
return _FDEV_ERR;
c = UDR;
/* behaviour similar to Unix stty ICRNL */
if (c == '\r')
c = '\n';
if (c == '\n')
{
*cp = c;
uart_putchar(c, stream);
rxp = b;
break;
}
else if (c == '\t')
c = ' ';
if ((c >= (uint8_t)' ' && c <= (uint8_t)'\x7e') ||
c >= (uint8_t)'\xa0')
{
if (cp == b + RX_BUFSIZE - 1)
uart_putchar('\a', stream);
else
{
*cp++ = c;
uart_putchar(c, stream);
}
continue;
}
switch (c)
{
case 'c' & 0x1f:
return -1;
case '\b':
case '\x7f':
if (cp > b)
{
uart_putchar('\b', stream);
uart_putchar(' ', stream);
uart_putchar('\b', stream);
cp--;
}
break;
case 'r' & 0x1f:
uart_putchar('\r', stream);
for (cp2 = b; cp2 < cp; cp2++)
uart_putchar(*cp2, stream);
break;
case 'u' & 0x1f:
while (cp > b)
{
uart_putchar('\b', stream);
uart_putchar(' ', stream);
uart_putchar('\b', stream);
cp--;
}
break;
case 'w' & 0x1f:
while (cp > b && cp[-1] != ' ')
{
uart_putchar('\b', stream);
uart_putchar(' ', stream);
uart_putchar('\b', stream);
cp--;
}
break;
}
}
c = *rxp++;
if (c == '\n')
rxp = 0;
return c;
}
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