// code by SASANO Takayoshi, CC BY-SA

#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <string.h>
#include <termios.h>
#include <fcntl.h>
#include <unistd.h>

static	void	tx_test(int fd)
{
	uint8_t	buf;

	while (1) {
		buf = rand();
		write(fd, &buf, sizeof(buf));
	}

	/* NOTREACHED */
}

static	int	setup_serial(int fd)
{
	struct termios	t;

	memset(&t, 0, sizeof(t));

	cfsetospeed(&t, 9600);
	cfsetispeed(&t, 9600);

	t.c_cflag = CREAD | CLOCAL | CS8;

	t.c_iflag = INPCK;
	t.c_oflag = 0;
	t.c_lflag = 0;

	t.c_cc[VTIME] = 0;
	t.c_cc[VMIN] = 1;

	tcflush(fd, TCIFLUSH);
	if (tcsetattr(fd, TCSANOW, &t) < 0) goto fail;

	return 0;
fail:
	return -1;
}

int	main(int argc, char *argv[])
{
	int	fd;

	if (argc < 2) {
		printf("%s [device]\n", argv[0]);
		goto fin0;
	}

	fd = open(argv[1], O_RDWR | O_NOCTTY | O_NDELAY);
	if (fd < 0) {
		printf("device open error\n");
		goto fin0;
	}

	if (setup_serial(fd) < 0) {
		printf("serial parameter error\n");
		goto fin1;
	}

	tx_test(fd);

fin1:
	close(fd);
fin0:
	return 0;
}