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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"

#include "main.h"

//

//  constants and macros

//

// 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_STATUS   UCSR1A

#define UART1_CONTROL  UCSR1B

#define UART1_DATA     UDR1

#define UART1_UDRIE    UDRIE1

//

//  module global variables

//

#if defined( ATMEGA_USART1 )

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;

#endif

//

// these functions are only for ATmegas with two USART

//

#if defined( ATMEGA_USART1 )

//--------------------------------------------------------------

// Function: UART1 Receive Complete interrupt

// Purpose:  called when the UART1 has received a character

//--------------------------------------------------------------

ISR(USART1_RX_vect)

{

        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;

}

//--------------------------------------------------------------

// Function: UART1 Data Register Empty interrupt

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

//--------------------------------------------------------------

ISR(USART1_UDRE_vect)

{

        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

}

//--------------------------------------------------------------

// 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;

}

//--------------------------------------------------------------

// Function: uart1_putc()

// Purpose:  write byte to ringbuffer for transmitting via UART

// Input:    byte to be transmitted

// Returns:  1 on succes, 0 if remote not ready

//--------------------------------------------------------------

int 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);

        return (UART1_LastRxError << 8) + data;

}

//--------------------------------------------------------------

// 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++);

}

//--------------------------------------------------------------

// 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);

}

//--------------------------------------------------------------

// Function: uart1_available()

// Purpose:  Determine the number of bytes waiting in the receive buffer

// Input:    None

// Returns:  Integer number of bytes in the receive buffer

//--------------------------------------------------------------

int uart1_available(void)

{

        return (UART_RX_BUFFER_MASK + UART1_RxHead - UART1_RxTail) % UART_RX_BUFFER_MASK;

}

//--------------------------------------------------------------

// Function: uart1_flush()

// Purpose:  Flush bytes waiting the receive buffer.  Acutally ignores them.

// Input:    None

// Returns:  None

//--------------------------------------------------------------

void uart1_flush(void)

{

        UART1_RxHead = UART1_RxTail;

}

#endif