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

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
 */