source: avrstuff/libs/usart/usart.c@ c956fd4

/* AVR USART acces functions - stolen from Extreme Electronics */

#include <avr/io.h>
#include <inttypes.h>

#ifndef BAUD
        #error You must define BAUD to use libuart.
#endif

// FIXME there are two USARTs in this case and we should be able to drive either

// Compatibility for devices with single USART only
#ifdef __AVR_ATmega8__
#define UBRR0H UBRRH
#define UBRR0L UBRRL
#define UCSR0A UCSRA
#define UCSR0C UCSRC
#define UCSR0B UCSRB
#define UDR0   UDR
#define UDRE0  UDRE
#define RXC0   RXC
#endif

#ifdef __AVR_AT90USB1287__
#define UBRR0H UBRR1H
#define UBRR0L UBRR1L
#define UCSR0A UCSR1A
#define UCSR0C UCSR1C
#define UCSR0B UCSR1B
#define UDR0   UDR1
#define UDRE0  UDRE1
#define RXC0   RXC1

#define RXEN   RXEN1
#define TXEN   TXEN1
#define U2X    U2X1
#endif

void USARTInit()
{
        //Set Baud rate
        #include <util/setbaud.h>
        UBRR0H = UBRRH_VALUE;
        UBRR0L = UBRRL_VALUE;
        #if USE_2X
                UCSR0A |= (1 << U2X);
        #else
                UCSR0A &= ~(1 << U2X);
        #endif

        /*Set Frame Format
          >> Asynchronous mode
          >> No Parity
          >> 1 StopBit
          >> char size 8
          */
#if defined(__AVR_ATtiny2313__)
        UCSRC = (1 << UCSZ1) | (1 << UCSZ0);
#elif defined __AVR_ATmega128__
        UCSR0C = (2 << UCSZ0) | (2 << UPM0) ; /* 7 bits + even parity.
                                                                                        TODO make this configurable. */
#elif defined(__AVR_AT90USB1287__)
        UCSR1C = (1 << UCSZ11) | (1 << UCSZ10);
#else
        UCSR0C = (1 << URSEL) | (3 << UCSZ0);
#endif

        //Enable The receiver and transmitter
        UCSR0B = (1 << RXEN) | (1 << TXEN);
}


void USARTWriteChar(char data)
{
        //Wait untill the transmitter is ready
        while(!(UCSR0A & (1<<UDRE0)))
        {
                //Do nothing
        }

        //Now write the data to USART buffer

        UDR0=data;
}


char USARTReadChar()
{
        //Wait untill a data is available
        while(!(UCSR0A & (1<<RXC0)))
        {
                //Do nothing
        }

        //Now USART has got data from host
        //and is available is buffer

        return UDR0;
}


void USARTWriteHex(unsigned char i)
{
        unsigned char k = i>>4;
        if (k <=9) k+='0';
        else k+=('A'-10);

        USARTWriteChar(k);

        k = i&0xF;
        if (k <=9) k+='0';
        else k+=('A'-10);

        USARTWriteChar(k);
}