#include <stdio.h>#include <avr/io.h>#include <avr/sfr_defs.h>#include "uart.h"/* some mcus have multiple uarts */#ifdef UDR0#define UBRRH UBRR0H#define UBRRL UBRR0L#define UDR UDR0#define UCSRA UCSR0A#define UDRE UDRE0#define RXC RXC0#define UCSRB UCSR0B#define RXEN RXEN0#define TXEN TXEN0#define UCSRC UCSR0C#define URSEL #define UCSZ0 UCSZ00#define UCSZ1 UCSZ01#define UCSRC_SELECT 0#else#define UCSRC_SELECT (1 << URSEL)#endif#define BAUD 9600UL#define UBRRVAL (F_CPU/(BAUD*16)-1)static int _uart_putc(char c, FILE* stream);static int _uart_getc(FILE* stream);static FILE stdio = FDEV_SETUP_STREAM(_uart_putc, _uart_getc, _FDEV_SETUP_RW);void uart_init(){    /* set baud rate */    UBRRH = UBRRVAL >> 8;    UBRRL = UBRRVAL & 0xff;    /* set frame format: 8 bit, no parity, 1 bit */    UCSRC = UCSRC_SELECT | (1 << UCSZ1) | (1 << UCSZ0);    /* enable serial receiver and transmitter */    UCSRB = (1 << RXEN) | (1 << TXEN);}void uart_connect_stdio(){    stdin = stdout = stderr = &stdio;}void uart_putc(uint8_t c){    if(c == '\n')        uart_putc('\r');    /* wait until transmit buffer is empty */    loop_until_bit_is_set(UCSRA, UDRE);    /* send next byte */    UDR = c;}int _uart_putc(char c, FILE* stream){    uart_putc(c);    return 0;}void uart_putc_hex(uint8_t b){    /* upper nibble */    if((b >> 4) < 0x0a)        uart_putc((b >> 4) + '0');    else        uart_putc((b >> 4) - 0x0a + 'a');    /* lower nibble */    if((b & 0x0f) < 0x0a)        uart_putc((b & 0x0f) + '0');    else        uart_putc((b & 0x0f) - 0x0a + 'a');}uint8_t uart_getc(){    /* wait until receive buffer is full */    loop_until_bit_is_set(UCSRA, RXC);    uint8_t b = UDR;    if(b == '\r')        b = '\n';    return b;}int _uart_getc(FILE* stream){    return uart_getc();}