avr_uart.c

Henriks AVR Boot Loader for AVR ATMEGA88 with xmodem and autoboot

/*
avr_uart.h

provide functions to set up uart

Copyright Henrik Bj鰎kman www.eit.se/hb 2007

This file is free software; you can redistribute it and/or modify it
under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
General Public License for more details.

If you do modify it please make a note about it in the history 
section below.

History

2005-02-16
Modified for atmega8 and renamed. 
Henrik Bj鰎kman

2007-03-15
Modified for atmega88.
Henrik Bj鰎kman

*/


/* -------------------------------------------------------------------------
 * BUGS
 * ------------------------------------------------------------------------- */
/*
// port_or is not defined in iomacro.h (which gets included in io.h) while
// __port_or has a definition. This seems to be a bug in iomacro.h
#define port_or __port_or
// ditto
#define port_and __port_and
*/

/* -------------------------------------------------------------------------
 * includes
 * ------------------------------------------------------------------------- */
#include <avr/io.h>
#include <avr/pgmspace.h>
#include <avr/wdt.h>
#include "avr_cfg.h"
#include "avr_uart.h"

/* compatibilty macros for old style */
/* for new design instead of "sbi(DDRC,PC5);" use "DDRC|= _BV(PC5);" */
#ifndef cbi
#define cbi(sfr, bit) (_SFR_BYTE(sfr) &= ~_BV(bit))
#endif

#ifndef sbi
#define sbi(sfr, bit) (_SFR_BYTE(sfr) |= _BV(bit))
#endif

#ifndef outp
#define outp(value,sfr) (_SFR_BYTE(sfr) = value)
#endif

#ifndef inp
#define inp(sfr) (_SFR_BYTE(sfr))
#endif



/* -------------------------------------------------------------------------
 * local variables and defines
 * ------------------------------------------------------------------------- */




#ifdef __AVR_ATmega8__
#define UART_OUTBUF_EMPTY() (!( UCSRA & (1<<UDRE)))
#define UART_INBUF_EMPTY() (!(UCSRA & (1<<RXC)))
#elif defined __AVR_ATmega88__
#define UART_OUTBUF_EMPTY() (!( UCSR0A & (1<<UDRE0)))
#define UART_INBUF_EMPTY() (!(UCSR0A & (1<<RXC0)))
#else
#error
#endif



void uart_init(void)
{
  //ubrr_value = 103;
  unsigned int ubrr_value = (AVR_FOSC/(16L*BAUDRATE))-1; // AVR_FOSC is larger than a 16 bit int so be carefull here;

#ifdef __AVR_ATmega8__

  /* Set baud rate */
  UBRRH = (unsigned char)(ubrr_value>>8);
  UBRRL = (unsigned char)ubrr_value;

  /* Enable receiver and transmitter */
  UCSRB = (1<<RXEN)|(1<<TXEN);

  /* Set frame format: 8data, 2stop bit */
  UCSRC = (1<<URSEL)|(1<<USBS)|(3<<UCSZ0);

  /* enable RX interrupt */
  //UCSRB |= (1<<RXCIE);


#elif defined __AVR_ATmega88__

  /* Set baud rate */
  UBRR0H = (unsigned char)(ubrr_value>>8);
  UBRR0L = (unsigned char)ubrr_value;

  /* Enable receiver and transmitter */
  UCSR0B = (1<<RXEN0)|(1<<TXEN0);

  /* Set frame format: 8data, 2stop bit */
  UCSR0C = (1<<USBS0)|(3<<UCSZ00);

  // URSEL not needed in atmega88?

  /* enable RX interrup */
  //UCSR0B |= (1<<RXCIE0);

#else
#error
#endif
}



/* send if not using interrupt */
void uart_putchar( unsigned char data )
{
  /* Wait for empty transmit buffer */
  while ( UART_OUTBUF_EMPTY() )
  {
    ;
  }

  /* Put data into buffer, sends the data */
#ifdef __AVR_ATmega8__
  UDR = data;
#elif defined __AVR_ATmega88__
  UDR0 = data;
#else
#error
#endif
}



/* receive if not using interrupt */
/* wait until a character is available */
unsigned char uart_waitchar( void )
{
  /* Wait for data to be received */
  while ( UART_INBUF_EMPTY() )
  {
#ifdef ENABLE_WDT
    wdt_reset();
#endif
  }

  /* Get and return received data from buffer */
#ifdef __AVR_ATmega8__
  return UDR;
#elif defined __AVR_ATmega88__
  return UDR0;
#else
#error
#endif
}

/* receive if not using interrupt */
/* return -1 if no character was available */
int uart_getchar(void)
{
  /* Wait for data to be received */
  if (UART_INBUF_EMPTY())
  {
#ifdef ENABLE_WDT
    wdt_reset();
#endif
	return -1;
  }

  /* Get and return received data from buffer */
#ifdef __AVR_ATmega8__
  return UDR;
#elif defined __AVR_ATmega88__
  return UDR0;
#else
#error
#endif
}



void uart_print_P(const char *addr)
{
  char c; 
  while ((c = pgm_read_byte(addr++))) 
  {
    uart_putchar(c);
  }
}