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/*************************************************************************

Title:    Interrupt UART library with receive/transmit circular buffers

Author:   Peter Fleury <pfleury@gmx.ch>   http://jump.to/fleury

File:     $Id: uart.c,v 1.6.2.2 2009/11/29 08:56:12 Peter Exp $

Software: AVR-GCC 4.1, AVR Libc 1.4.6 or higher

Hardware: any AVR with built-in UART,

License:  GNU General Public License

DESCRIPTION:

    An interrupt is generated when the UART has finished transmitting or

    receiving a byte. The interrupt handling routines use circular buffers

    for buffering received and transmitted data.

    The UART_RX_BUFFER_SIZE and UART_TX_BUFFER_SIZE variables define

    the buffer size in bytes. Note that these variables must be a

    power of 2.

USAGE:

    Refere to the header file uart.h for a description of the routines.

    See also example test_uart.c.

NOTES:

    Based on Atmel Application Note AVR306

LICENSE:

    Copyright (C) 2006 Peter Fleury

    This program 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

    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.

*************************************************************************/

#include <avr/io.h>

#include <avr/interrupt.h>

#include <avr/pgmspace.h>

#include "uart1.h"

/*

 *  constants and macros

 */

//#define __AVR_ATmega644P__

/* size of RX/TX buffers */

#define UART_RX_BUFFER_MASK ( UART_RX_BUFFER_SIZE - 1)

#define UART_TX_BUFFER_MASK ( UART_TX_BUFFER_SIZE - 1)

#if ( UART_RX_BUFFER_SIZE & UART_RX_BUFFER_MASK )

#error RX buffer size is not a power of 2

#endif

#if ( UART_TX_BUFFER_SIZE & UART_TX_BUFFER_MASK )

#error TX buffer size is not a power of 2

#endif

 /* ATmega with two USART */

 #define ATMEGA_USART1

 #define UART1_RECEIVE_INTERRUPT   SIG_USART1_RECV

 #define UART1_TRANSMIT_INTERRUPT  SIG_USART1_DATA

 #define UART1_STATUS   UCSR1A

 #define UART1_CONTROL  UCSR1B

 #define UART1_DATA     UDR1

 #define UART1_UDRIE    UDRIE1

/*

 *  module global variables

 */

static volatile unsigned char UART1_TxBuf[UART_TX_BUFFER_SIZE];

static volatile unsigned char UART1_RxBuf[UART_RX_BUFFER_SIZE];

static volatile unsigned char UART1_TxHead;

static volatile unsigned char UART1_TxTail;

static volatile unsigned char UART1_RxHead;

static volatile unsigned char UART1_RxTail;

static volatile unsigned char UART1_LastRxError;

/*

 * these functions are only for ATmegas with two USART

 */

SIGNAL(UART1_RECEIVE_INTERRUPT)

/*************************************************************************

Function: UART1 Receive Complete interrupt

Purpose:  called when the UART1 has received a character

**************************************************************************/

{

    unsigned char tmphead;

    unsigned char data;

    unsigned char usr;

    unsigned char lastRxError;

    /* read UART status register and UART data register */

    usr  = UART1_STATUS;

    data = UART1_DATA;

    /* */

    lastRxError = (usr & (_BV(FE1)|_BV(DOR1)) );

    /* calculate buffer index */

    tmphead = ( UART1_RxHead + 1) & UART_RX_BUFFER_MASK;

    if ( tmphead == UART1_RxTail ) {

        /* error: receive buffer overflow */

        lastRxError = UART_BUFFER_OVERFLOW >> 8;

    }else{

        /* store new index */

        UART1_RxHead = tmphead;

        /* store received data in buffer */

        UART1_RxBuf[tmphead] = data;

    }

    UART1_LastRxError = lastRxError;  

}

SIGNAL(UART1_TRANSMIT_INTERRUPT)

/*************************************************************************

Function: UART1 Data Register Empty interrupt

Purpose:  called when the UART1 is ready to transmit the next byte

**************************************************************************/

{

    unsigned char tmptail;

    if ( UART1_TxHead != UART1_TxTail) {

        /* calculate and store new buffer index */

        tmptail = (UART1_TxTail + 1) & UART_TX_BUFFER_MASK;

        UART1_TxTail = tmptail;

        /* get one byte from buffer and write it to UART */

        UART1_DATA = UART1_TxBuf[tmptail];  /* start transmission */

    }else{

        /* tx buffer empty, disable UDRE interrupt */

        UART1_CONTROL &= ~_BV(UART1_UDRIE);

    }

}

/*************************************************************************

Function: uart1_init()

Purpose:  initialize UART1 and set baudrate

Input:    baudrate using macro UART_BAUD_SELECT()

Returns:  none

**************************************************************************/

void uart1_init(unsigned int baudrate)

{

    UART1_TxHead = 0;

    UART1_TxTail = 0;

    UART1_RxHead = 0;

    UART1_RxTail = 0;

    /* Set baud rate */

    if ( baudrate & 0x8000 )

    {

        UART1_STATUS = (1<<U2X1);  //Enable 2x speed 

      baudrate &= ~0x8000;

    }

    UBRR1H = (unsigned char)(baudrate>>8);

    UBRR1L = (unsigned char) baudrate;

    /* Enable USART receiver and transmitter and receive complete interrupt */

    UART1_CONTROL = _BV(RXCIE1)|(1<<RXEN1)|(1<<TXEN1);

    /* Set frame format: asynchronous, 8data, no parity, 1stop bit */  

    #ifdef URSEL1

    UCSR1C = (1<<URSEL1)|(3<<UCSZ10);

    #else

    UCSR1C = (3<<UCSZ10);

    #endif 

}/* uart_init */

/*************************************************************************

Function: uart1_getc()

Purpose:  return byte from ringbuffer  

Returns:  lower byte:  received byte from ringbuffer

          higher byte: last receive error

**************************************************************************/

unsigned int uart1_getc(void)

{    

    unsigned char tmptail;

    unsigned char data;

    if ( UART1_RxHead == UART1_RxTail ) {

        return UART_NO_DATA;   /* no data available */

    }

    /* calculate /store buffer index */

    tmptail = (UART1_RxTail + 1) & UART_RX_BUFFER_MASK;

    UART1_RxTail = tmptail;

    /* get data from receive buffer */

    data = UART1_RxBuf[tmptail];

    return (UART1_LastRxError << 8) + data;

}/* uart1_getc */

/*************************************************************************

Function: uart1_putc()

Purpose:  write byte to ringbuffer for transmitting via UART

Input:    byte to be transmitted

Returns:  none          

**************************************************************************/

void uart1_putc(unsigned char data)

{

    unsigned char tmphead;

    tmphead  = (UART1_TxHead + 1) & UART_TX_BUFFER_MASK;

    while ( tmphead == UART1_TxTail ){

        ;/* wait for free space in buffer */

    }

    UART1_TxBuf[tmphead] = data;

    UART1_TxHead = tmphead;

    /* enable UDRE interrupt */

    UART1_CONTROL    |= _BV(UART1_UDRIE);

}/* uart1_putc */

/*************************************************************************

Function: uart1_puts()

Purpose:  transmit string to UART1

Input:    string to be transmitted

Returns:  none          

**************************************************************************/

void uart1_puts(const char *s )

{

    while (*s)

      uart1_putc(*s++);

}/* uart1_puts */

/*************************************************************************

Function: uart1_puts_p()

Purpose:  transmit string from program memory to UART1

Input:    program memory string to be transmitted

Returns:  none

**************************************************************************/

void uart1_puts_p(const char *progmem_s )

{

    register char c;

    while ( (c = pgm_read_byte(progmem_s++)) )

      uart1_putc(c);

}/* uart1_puts_p */