make printf work (arduino)

fix-printf.c

// from https://forum.arduino.cc/index.php?topic=149785.msg1125620#msg1125620

#include "fix-printf.h"

#include <stdlib.h>

#if ARDUINO >= 100
#include "Arduino.h"
#else
#include "WProgram.h"
#endif



// Function that printf and related will use to print
static int serial_putchar(char c, FILE *f)
{
	(void)(f);
	Serial.write(c);
	return 1;
}

// Function that scanf and related will use to read
static int serial_getchar(FILE *)
{
	// Wait until character is avilable
	while(Serial.available() <= 0) {}

	return Serial.read();
}


extern "C" {
	#include <stdio.h>
	void stdio_init()
	{
		static FILE serial_stdinout = { .buf = NULL, .unget = 0, .flags = _FDEV_SETUP_RW, .size = 0, .len = 0, .put = serial_putchar, .get = serial_getchar, .udata = 0 };

		// Set up stdout and stdin
		stdout = &serial_stdinout;
		stdin  = &serial_stdinout;
		stderr = &serial_stdinout;
	}
}