uart/uart.cpp

/*************************************************************************
Title:    Interrupt UART library with receive/transmit circular buffers
Author:   Peter Fleury <pfleury@gmx.ch>   http://tinyurl.com/peterfleury
File:     $Id: uart.c,v 1.15.2.4 2015/09/05 18:33:32 peter Exp $
Software: AVR-GCC 4.x
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) 2015 Peter Fleury, GNU General Public License Version 3

    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 "uart.h"
#include <avr/interrupt.h>
#include <avr/io.h>
#include <avr/pgmspace.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

#if defined(__AVR_AT90S2313__) || defined(__AVR_AT90S4414__) || defined(__AVR_AT90S8515__) || \
    defined(__AVR_AT90S4434__) || defined(__AVR_AT90S8535__) || defined(__AVR_ATmega103__)
/* old AVR classic or ATmega103 with one UART */
#define UART0_RECEIVE_INTERRUPT UART_RX_vect
#define UART0_TRANSMIT_INTERRUPT UART_UDRE_vect
#define UART0_STATUS USR
#define UART0_CONTROL UCR
#define UART0_DATA UDR
#define UART0_UDRIE UDRIE
#define UART0_UBRRL UBRR
#define UART0_BIT_U2X U2X
#define UART0_BIT_RXCIE RXCIE
#define UART0_BIT_RXEN RXEN
#define UART0_BIT_TXEN TXEN
#elif defined(__AVR_AT90S2333__) || defined(__AVR_AT90S4433__)
/* old AVR classic with one UART */
#define UART0_RECEIVE_INTERRUPT UART_RX_vect
#define UART0_TRANSMIT_INTERRUPT UART_UDRE_vect
#define UART0_STATUS UCSRA
#define UART0_CONTROL UCSRB
#define UART0_DATA UDR
#define UART0_UDRIE UDRIE
#define UART0_UBRRL UBRR
#define UART0_BIT_U2X U2X
#define UART0_BIT_RXCIE RXCIE
#define UART0_BIT_RXEN RXEN
#define UART0_BIT_TXEN TXEN
#elif defined(__AVR_AT90PWM216__) || defined(__AVR_AT90PWM316__)
/* AT90PWN216/316 with one USART */
#define UART0_RECEIVE_INTERRUPT USART_RX_vect
#define UART0_TRANSMIT_INTERRUPT USART_UDRE_vect
#define UART0_STATUS UCSRA
#define UART0_CONTROL UCSRB
#define UART0_CONTROLC UCSRC
#define UART0_DATA UDR
#define UART0_UDRIE UDRIE
#define UART0_UBRRL UBRRL
#define UART0_UBRRH UBRRH
#define UART0_BIT_U2X U2X
#define UART0_BIT_RXCIE RXCIE
#define UART0_BIT_RXEN RXEN
#define UART0_BIT_TXEN TXEN
#define UART0_BIT_UCSZ0 UCSZ0
#define UART0_BIT_UCSZ1 UCSZ1
#elif defined(__AVR_ATmega8__) || defined(__AVR_ATmega8A__) || defined(__AVR_ATmega16__) || \
    defined(__AVR_ATmega16A__) || defined(__AVR_ATmega32__) || defined(__AVR_ATmega32A__) || \
    defined(__AVR_ATmega323__)
/* ATmega with one USART */
#define UART0_RECEIVE_INTERRUPT USART_RXC_vect
#define UART0_TRANSMIT_INTERRUPT USART_UDRE_vect
#define UART0_STATUS UCSRA
#define UART0_CONTROL UCSRB
#define UART0_CONTROLC UCSRC
#define UART0_DATA UDR
#define UART0_UDRIE UDRIE
#define UART0_UBRRL UBRRL
#define UART0_UBRRH UBRRH
#define UART0_BIT_U2X U2X
#define UART0_BIT_RXCIE RXCIE
#define UART0_BIT_RXEN RXEN
#define UART0_BIT_TXEN TXEN
#define UART0_BIT_UCSZ0 UCSZ0
#define UART0_BIT_UCSZ1 UCSZ1
#define UART0_BIT_URSEL URSEL
#elif defined(__AVR_ATmega8515__) || defined(__AVR_ATmega8535__)
#define UART0_RECEIVE_INTERRUPT USART_RX_vect
#define UART0_TRANSMIT_INTERRUPT USART_UDRE_vect
#define UART0_STATUS UCSRA
#define UART0_CONTROL UCSRB
#define UART0_CONTROLC UCSRC
#define UART0_DATA UDR
#define UART0_UDRIE UDRIE
#define UART0_UBRRL UBRRL
#define UART0_UBRRH UBRRH
#define UART0_BIT_U2X U2X
#define UART0_BIT_RXCIE RXCIE
#define UART0_BIT_RXEN RXEN
#define UART0_BIT_TXEN TXEN
#define UART0_BIT_UCSZ0 UCSZ0
#define UART0_BIT_UCSZ1 UCSZ1
#define UART0_BIT_URSEL URSEL
#elif defined(__AVR_ATmega163__)
/* ATmega163 with one UART */
#define UART0_RECEIVE_INTERRUPT UART_RX_vect
#define UART0_TRANSMIT_INTERRUPT UART_UDRE_vect
#define UART0_STATUS UCSRA
#define UART0_CONTROL UCSRB
#define UART0_DATA UDR
#define UART0_UDRIE UDRIE
#define UART0_UBRRL UBRR
#define UART0_UBRRH UBRRHI
#define UART0_BIT_U2X U2X
#define UART0_BIT_RXCIE RXCIE
#define UART0_BIT_RXEN RXEN
#define UART0_BIT_TXEN TXEN
#elif defined(__AVR_ATmega162__)
/* ATmega with two USART */
#define ATMEGA_USART1
#define UART0_RECEIVE_INTERRUPT USART0_RXC_vect
#define UART1_RECEIVE_INTERRUPT USART1_RXC_vect
#define UART0_TRANSMIT_INTERRUPT USART0_UDRE_vect
#define UART1_TRANSMIT_INTERRUPT USART1_UDRE_vect
#define UART0_STATUS UCSR0A
#define UART0_CONTROL UCSR0B
#define UART0_CONTROLC UCSR0C
#define UART0_DATA UDR0
#define UART0_UDRIE UDRIE0
#define UART0_UBRRL UBRR0L
#define UART0_UBRRH UBRR0H
#define UART0_BIT_URSEL URSEL0
#define UART0_BIT_U2X U2X0
#define UART0_BIT_RXCIE RXCIE0
#define UART0_BIT_RXEN RXEN0
#define UART0_BIT_TXEN TXEN0
#define UART0_BIT_UCSZ0 UCSZ00
#define UART0_BIT_UCSZ1 UCSZ01
#define UART1_STATUS UCSR1A
#define UART1_CONTROL UCSR1B
#define UART1_CONTROLC UCSR1C
#define UART1_DATA UDR1
#define UART1_UDRIE UDRIE1
#define UART1_UBRRL UBRR1L
#define UART1_UBRRH UBRR1H
#define UART1_BIT_URSEL URSEL1
#define UART1_BIT_U2X U2X1
#define UART1_BIT_RXCIE RXCIE1
#define UART1_BIT_RXEN RXEN1
#define UART1_BIT_TXEN TXEN1
#define UART1_BIT_UCSZ0 UCSZ10
#define UART1_BIT_UCSZ1 UCSZ11
#elif defined(__AVR_ATmega161__)
/* ATmega with UART */
#error "AVR ATmega161 currently not supported by this libaray !"
#elif defined(__AVR_ATmega169__)
/* ATmega with one USART */
#define UART0_RECEIVE_INTERRUPT USART0_RX_vect
#define UART0_TRANSMIT_INTERRUPT USART0_UDRE_vect
#define UART0_STATUS UCSRA
#define UART0_CONTROL UCSRB
#define UART0_CONTROLC UCSRC
#define UART0_DATA UDR
#define UART0_UDRIE UDRIE
#define UART0_UBRRL UBRRL
#define UART0_UBRRH UBRRH
#define UART0_BIT_U2X U2X
#define UART0_BIT_RXCIE RXCIE
#define UART0_BIT_RXEN RXEN
#define UART0_BIT_TXEN TXEN
#define UART0_BIT_UCSZ0 UCSZ0
#define UART0_BIT_UCSZ1 UCSZ1
#elif defined(__AVR_ATmega48__) || defined(__AVR_ATmega48A__) || defined(__AVR_ATmega48P__) || \
    defined(__AVR_ATmega48PA__) || defined(__AVR_ATmega48PB__) || defined(__AVR_ATmega88__) || \
    defined(__AVR_ATmega88A__) || defined(__AVR_ATmega88P__) || defined(__AVR_ATmega88PA__) || \
    defined(__AVR_ATmega88PB__) || defined(__AVR_ATmega168__) || defined(__AVR_ATmega168A__) || \
    defined(__AVR_ATmega168P__) || defined(__AVR_ATmega168PA__) || defined(__AVR_ATmega168PB__) || \
    defined(__AVR_ATmega328__) || defined(__AVR_ATmega328P__) || defined(__AVR_ATmega3250__) || \
    defined(__AVR_ATmega3290__) || defined(__AVR_ATmega6450__) || defined(__AVR_ATmega6490__)
/* ATmega with one USART */
#define UART0_RECEIVE_INTERRUPT USART_RX_vect
#define UART0_TRANSMIT_INTERRUPT USART_UDRE_vect
#define UART0_STATUS UCSR0A
#define UART0_CONTROL UCSR0B
#define UART0_CONTROLC UCSR0C
#define UART0_DATA UDR0
#define UART0_UDRIE UDRIE0
#define UART0_UBRRL UBRR0L
#define UART0_UBRRH UBRR0H
#define UART0_BIT_U2X U2X0
#define UART0_BIT_RXCIE RXCIE0
#define UART0_BIT_RXEN RXEN0
#define UART0_BIT_TXEN TXEN0
#define UART0_BIT_UCSZ0 UCSZ00
#define UART0_BIT_UCSZ1 UCSZ01
#elif defined(__AVR_ATtiny2313__) || defined(__AVR_ATtiny2313A__) || defined(__AVR_ATtiny4313__)
/* ATtiny with one USART */
#define UART0_RECEIVE_INTERRUPT USART_RX_vect
#define UART0_TRANSMIT_INTERRUPT USART_UDRE_vect
#define UART0_STATUS UCSRA
#define UART0_CONTROL UCSRB
#define UART0_CONTROLC UCSRC
#define UART0_DATA UDR
#define UART0_UDRIE UDRIE
#define UART0_UBRRL UBRRL
#define UART0_UBRRH UBRRH
#define UART0_BIT_U2X U2X
#define UART0_BIT_RXCIE RXCIE
#define UART0_BIT_RXEN RXEN
#define UART0_BIT_TXEN TXEN
#define UART0_BIT_UCSZ0 UCSZ0
#define UART0_BIT_UCSZ1 UCSZ1
#elif defined(__AVR_ATmega329__) || defined(__AVR_ATmega649__) || defined(__AVR_ATmega3290__) || \
    defined(__AVR_ATmega6490__) || defined(__AVR_ATmega169A__) || defined(__AVR_ATmega169PA__) || \
    defined(__AVR_ATmega329A__) || defined(__AVR_ATmega329PA__) || defined(__AVR_ATmega3290A__) || \
    defined(__AVR_ATmega3290PA__) || defined(__AVR_ATmega649A__) || defined(__AVR_ATmega649P__) || \
    defined(__AVR_ATmega6490A__) || defined(__AVR_ATmega6490P__) || defined(__AVR_ATmega165__) || \
    defined(__AVR_ATmega325__) || defined(__AVR_ATmega645__) || defined(__AVR_ATmega3250__) || \
    defined(__AVR_ATmega6450__) || defined(__AVR_ATmega165A__) || defined(__AVR_ATmega165PA__) || \
    defined(__AVR_ATmega325A__) || defined(__AVR_ATmega325PA__) || defined(__AVR_ATmega3250A__) || \
    defined(__AVR_ATmega3250PA__) || defined(__AVR_ATmega645A__) || defined(__AVR_ATmega645PA__) || \
    defined(__AVR_ATmega6450A__) || defined(__AVR_ATmega6450PA__) || defined(__AVR_ATmega644__)
/* ATmega with one USART */
#define UART0_RECEIVE_INTERRUPT USART0_RX_vect
#define UART0_TRANSMIT_INTERRUPT USART0_UDRE_vect
#define UART0_STATUS UCSR0A
#define UART0_CONTROL UCSR0B
#define UART0_CONTROLC UCSR0C
#define UART0_DATA UDR0
#define UART0_UDRIE UDRIE0
#define UART0_UBRRL UBRR0L
#define UART0_UBRRH UBRR0H
#define UART0_BIT_U2X U2X0
#define UART0_BIT_RXCIE RXCIE0
#define UART0_BIT_RXEN RXEN0
#define UART0_BIT_TXEN TXEN0
#define UART0_BIT_UCSZ0 UCSZ00
#define UART0_BIT_UCSZ1 UCSZ01
#elif defined(__AVR_ATmega64__) || defined(__AVR_ATmega128__) || defined(__AVR_ATmega128A__) || \
    defined(__AVR_ATmega640__) || defined(__AVR_ATmega1280__) || defined(__AVR_ATmega1281__) || \
    defined(__AVR_ATmega2560__) || defined(__AVR_ATmega2561__) || defined(__AVR_ATmega164P__) || \
    defined(__AVR_ATmega324P__) || defined(__AVR_ATmega644P__) || defined(__AVR_ATmega164A__) || \
    defined(__AVR_ATmega164PA__) || defined(__AVR_ATmega324A__) || defined(__AVR_ATmega324PA__) || \
    defined(__AVR_ATmega644A__) || defined(__AVR_ATmega644PA__) || defined(__AVR_ATmega1284__) || \
    defined(__AVR_ATmega1284P__) || defined(__AVR_ATtiny1634__)
/* ATmega with two USART */
#define ATMEGA_USART1
#define UART0_RECEIVE_INTERRUPT USART0_RX_vect
#define UART1_RECEIVE_INTERRUPT USART1_RX_vect
#define UART0_TRANSMIT_INTERRUPT USART0_UDRE_vect
#define UART1_TRANSMIT_INTERRUPT USART1_UDRE_vect
#define UART0_STATUS UCSR0A
#define UART0_CONTROL UCSR0B
#define UART0_CONTROLC UCSR0C
#define UART0_DATA UDR0
#define UART0_UDRIE UDRIE0
#define UART0_UBRRL UBRR0L
#define UART0_UBRRH UBRR0H
#define UART0_BIT_U2X U2X0
#define UART0_BIT_RXCIE RXCIE0
#define UART0_BIT_RXEN RXEN0
#define UART0_BIT_TXEN TXEN0
#define UART0_BIT_UCSZ0 UCSZ00
#define UART0_BIT_UCSZ1 UCSZ01
#define UART1_STATUS UCSR1A
#define UART1_CONTROL UCSR1B
#define UART1_CONTROLC UCSR1C
#define UART1_DATA UDR1
#define UART1_UDRIE UDRIE1
#define UART1_UBRRL UBRR1L
#define UART1_UBRRH UBRR1H
#define UART1_BIT_U2X U2X1
#define UART1_BIT_RXCIE RXCIE1
#define UART1_BIT_RXEN RXEN1
#define UART1_BIT_TXEN TXEN1
#define UART1_BIT_UCSZ0 UCSZ10
#define UART1_BIT_UCSZ1 UCSZ11
#elif defined(__AVR_ATmega8U2__) || defined(__AVR_ATmega16U2__) || defined(__AVR_ATmega32U2__) || \
    defined(__AVR_ATmega16U4__) || defined(__AVR_ATmega32U4__) || defined(__AVR_AT90USB82__) || \
    defined(__AVR_AT90USB162__) || defined(__AVR_AT90USB646__) || defined(__AVR_AT90USB1286__) || \
    defined(__AVR_AT90USB647__) || defined(__AVR_AT90USB1287__)
#define UART0_RECEIVE_INTERRUPT USART1_RX_vect
#define UART0_TRANSMIT_INTERRUPT USART1_UDRE_vect
#define UART0_STATUS UCSR1A
#define UART0_CONTROL UCSR1B
#define UART0_CONTROLC UCSR1C
#define UART0_DATA UDR1
#define UART0_UDRIE UDRIE1
#define UART0_UBRRL UBRR1L
#define UART0_UBRRH UBRR1H
#define UART0_BIT_U2X U2X1
#define UART0_BIT_RXCIE RXCIE1
#define UART0_BIT_RXEN RXEN1
#define UART0_BIT_TXEN TXEN1
#define UART0_BIT_UCSZ0 UCSZ10
#define UART0_BIT_UCSZ1 UCSZ11
#else
#error "no UART definition for MCU available"
#endif

/*
 *  module global variables
 */
static volatile unsigned char UART_TxBuf[UART_TX_BUFFER_SIZE];
static volatile unsigned char UART_RxBuf[UART_RX_BUFFER_SIZE];
static volatile unsigned char UART_TxHead;
static volatile unsigned char UART_TxTail;
static volatile unsigned char UART_RxHead;
static volatile unsigned char UART_RxTail;
static volatile unsigned char UART_LastRxError;

#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

ISR(UART0_RECEIVE_INTERRUPT)
/*************************************************************************
Function: UART Receive Complete interrupt
Purpose:  called when the UART 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 = UART0_STATUS;
	data = UART0_DATA;

	/* get FEn (Frame Error) DORn (Data OverRun) UPEn (USART Parity Error) bits */
#if defined(FE) && defined(DOR) && defined(UPE)
	lastRxError = usr & (_BV(FE) | _BV(DOR) | _BV(UPE));
#elif defined(FE0) && defined(DOR0) && defined(UPE0)
	lastRxError = usr & (_BV(FE0) | _BV(DOR0) | _BV(UPE0));
#elif defined(FE1) && defined(DOR1) && defined(UPE1)
	lastRxError = usr & (_BV(FE1) | _BV(DOR1) | _BV(UPE1));
#elif defined(FE) && defined(DOR)
	lastRxError = usr & (_BV(FE) | _BV(DOR));
#endif

	/* calculate buffer index */
	tmphead = (UART_RxHead + 1) & UART_RX_BUFFER_MASK;

	if (tmphead == UART_RxTail) {
		/* error: receive buffer overflow */
		lastRxError = UART_BUFFER_OVERFLOW >> 8;
	} else {
		/* store new index */
		UART_RxHead = tmphead;
		/* store received data in buffer */
		UART_RxBuf[tmphead] = data;
	}
	UART_LastRxError |= lastRxError;
}

ISR(UART0_TRANSMIT_INTERRUPT)
/*************************************************************************
Function: UART Data Register Empty interrupt
Purpose:  called when the UART is ready to transmit the next byte
**************************************************************************/
{
	unsigned char tmptail;

	if (UART_TxHead != UART_TxTail) {
		/* calculate and store new buffer index */
		tmptail = (UART_TxTail + 1) & UART_TX_BUFFER_MASK;
		UART_TxTail = tmptail;
		/* get one byte from buffer and write it to UART */
		UART0_DATA = UART_TxBuf[tmptail]; /* start transmission */
	} else {
		/* tx buffer empty, disable UDRE interrupt */
		UART0_CONTROL &= ~_BV(UART0_UDRIE);
	}
}

/*************************************************************************
Function: uart_init()
Purpose:  initialize UART and set baudrate
Input:    baudrate using macro UART_BAUD_SELECT()
Returns:  none
**************************************************************************/
void uart_init(unsigned int baudrate)
{
	UART_TxHead = 0;
	UART_TxTail = 0;
	UART_RxHead = 0;
	UART_RxTail = 0;

#ifdef UART_TEST
#ifndef UART0_BIT_U2X
#warning "UART0_BIT_U2X not defined"
#endif
#ifndef UART0_UBRRH
#warning "UART0_UBRRH not defined"
#endif
#ifndef UART0_CONTROLC
#warning "UART0_CONTROLC not defined"
#endif
#if defined(URSEL) || defined(URSEL0)
#ifndef UART0_BIT_URSEL
#warning "UART0_BIT_URSEL not defined"
#endif
#endif
#endif

	/* Set baud rate */
	if (baudrate & 0x8000) {
#if UART0_BIT_U2X
		UART0_STATUS = (1 << UART0_BIT_U2X); // Enable 2x speed
#endif
	}
#if defined(UART0_UBRRH)
	UART0_UBRRH = (unsigned char)((baudrate >> 8) & 0x80);
#endif
	UART0_UBRRL = (unsigned char)(baudrate & 0x00FF);

	/* Enable USART receiver and transmitter and receive complete interrupt */
	UART0_CONTROL = _BV(UART0_BIT_RXCIE) | (1 << UART0_BIT_RXEN) | (1 << UART0_BIT_TXEN);

/* Set frame format: asynchronous, 8data, no parity, 1stop bit */
#ifdef UART0_CONTROLC
#ifdef UART0_BIT_URSEL
	UART0_CONTROLC = (1 << UART0_BIT_URSEL) | (1 << UART0_BIT_UCSZ1) | (1 << UART0_BIT_UCSZ0);
#else
	UART0_CONTROLC = (1 << UART0_BIT_UCSZ1) | (1 << UART0_BIT_UCSZ0);
#endif
#endif

} /* uart_init */

/*************************************************************************
Function: uart_getc()
Purpose:  return byte from ringbuffer
Returns:  lower byte:  received byte from ringbuffer
          higher byte: last receive error
**************************************************************************/
unsigned int uart_getc(void)
{
	unsigned char tmptail;
	unsigned char data;
	unsigned char lastRxError;

	if (UART_RxHead == UART_RxTail) {
		return UART_NO_DATA; /* no data available */
	}

	/* calculate buffer index */
	tmptail = (UART_RxTail + 1) & UART_RX_BUFFER_MASK;

	/* get data from receive buffer */
	data = UART_RxBuf[tmptail];
	lastRxError = UART_LastRxError;

	/* store buffer index */
	UART_RxTail = tmptail;

	UART_LastRxError = 0;
	return (lastRxError << 8) + data;

} /* uart_getc */

/*************************************************************************
Function: uart_putc()
Purpose:  write byte to ringbuffer for transmitting via UART
Input:    byte to be transmitted
Returns:  none
**************************************************************************/
void uart_putc(unsigned char data)
{
	unsigned char tmphead;

	tmphead = (UART_TxHead + 1) & UART_TX_BUFFER_MASK;

	while (tmphead == UART_TxTail) {
		; /* wait for free space in buffer */
	}

	UART_TxBuf[tmphead] = data;
	UART_TxHead = tmphead;

	/* enable UDRE interrupt */
	UART0_CONTROL |= _BV(UART0_UDRIE);

} /* uart_putc */

/*************************************************************************
Function: uart_puts()
Purpose:  transmit string to UART
Input:    string to be transmitted
Returns:  none
**************************************************************************/
void uart_puts(const char *s)
{
	while (*s)
		uart_putc(*s++);

} /* uart_puts */

/*************************************************************************
Function: uart_puts_p()
Purpose:  transmit string from program memory to UART
Input:    program memory string to be transmitted
Returns:  none
**************************************************************************/
void uart_puts_p(const char *progmem_s)
{
	register char c;

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

} /* uart_puts_p */

/*
 * these functions are only for ATmegas with two USART
 */
#if defined(ATMEGA_USART1)

ISR(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;

	/* get FEn (Frame Error) DORn (Data OverRun) UPEn (USART Parity Error) bits */
	lastRxError = usr & (_BV(FE1) | _BV(DOR1) | _BV(UPE1));

	/* 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;
}

ISR(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;

#ifdef UART_TEST
#ifndef UART1_BIT_U2X
#warning "UART1_BIT_U2X not defined"
#endif
#ifndef UART1_UBRRH
#warning "UART1_UBRRH not defined"
#endif
#ifndef UART1_CONTROLC
#warning "UART1_CONTROLC not defined"
#endif
#if defined(URSEL) || defined(URSEL1)
#ifndef UART1_BIT_URSEL
#warning "UART1_BIT_URSEL not defined"
#endif
#endif
#endif

	/* Set baud rate */
	if (baudrate & 0x8000) {
#if UART1_BIT_U2X
		UART1_STATUS = (1 << UART1_BIT_U2X); // Enable 2x speed
#endif
	}
	UART1_UBRRH = (unsigned char)((baudrate >> 8) & 0x80);
	UART1_UBRRL = (unsigned char)baudrate;

	/* Enable USART receiver and transmitter and receive complete interrupt */
	UART1_CONTROL = _BV(UART1_BIT_RXCIE) | (1 << UART1_BIT_RXEN) | (1 << UART1_BIT_TXEN);

/* Set frame format: asynchronous, 8data, no parity, 1stop bit */
#ifdef UART1_BIT_URSEL
	UART1_CONTROLC = (1 << UART1_BIT_URSEL) | (1 << UART1_BIT_UCSZ1) | (1 << UART1_BIT_UCSZ0);
#else
	UART1_CONTROLC = (1 << UART1_BIT_UCSZ1) | (1 << UART1_BIT_UCSZ0);
#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 int data;
	unsigned char lastRxError;

	if (UART1_RxHead == UART1_RxTail) {
		return UART_NO_DATA; /* no data available */
	}

	/* calculate buffer index */
	tmptail = (UART1_RxTail + 1) & UART_RX_BUFFER_MASK;

	/* get data from receive buffer */
	data = UART1_RxBuf[tmptail];
	lastRxError = UART1_LastRxError;

	/* store buffer index */
	UART1_RxTail = tmptail;

	UART1_LastRxError = 0;
	return (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 */

#endif