arduino_stdout_retarget.ino

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

void usart_putchar(char data);
int usart_putchar_printf(char var, FILE *stream);

static FILE mystdout; /* FDEV_SETUP_STREAM(usart_putchar_printf, NULL, _FDEV_SETUP_WRITE); */

void usart_putchar(char data)
{
    // Wait for empty transmit buffer
    while ( !( UCSR0A & (1 << UDRE0)) ) ;
    // Put data into buffer, sends the data
    UDR0 = (unsigned char)data;
}


// this function is called by printf as a stream handler
int usart_putchar_printf(char var, FILE *stream)
{
    // translate \n to \r for br@y++ terminal
    if (var == '\n') usart_putchar('\r');
    usart_putchar(var);
    return 0;
}

void retarget_stdio(void)
{
    // setup our stdio stream

    mystdout.put = usart_putchar_printf;
    mystdout.get = NULL;
    mystdout.flags = _FDEV_SETUP_WRITE;
    mystdout.udata = 0;

    stdout = &mystdout;
}


void setup(void)
{
    Serial.begin(19200);
    retarget_stdio();
    
    puts("*** START ***");
}

void loop(void)
{
    static uint32_t count = 0;
    static float realnum = 0.23;
    printf("count = %04u\r\n", count++);
    printf("real number = %7.2f\r\n\r\n", realnum);
    realnum += 1.47;

    delay(1000);
}