#include<stdio.h>
#include<errno.h>
#include<termios.h>
#include<unistd.h>
#include<sys/stat.h>
#include<fcntl.h>

int tty_set(int tty)
{
	struct termios tty_opts;
	int foo;
	
	foo=tcgetattr(tty,&tty_opts);
	if(foo<0) return -1;
	
	foo=cfsetispeed(&tty_opts,B9600);
	if(foo<0) return -2;
	
	foo=cfsetospeed(&tty_opts,B9600);
	if(foo<0) return -3;
	
	//3
	// 8N1
	tty_opts.c_cflag &= ~PARENB;
	tty_opts.c_cflag &= ~CSTOPB;
	tty_opts.c_cflag &= ~CSIZE;
	tty_opts.c_cflag |= CS8;
	// no flow control
	tty_opts.c_cflag &= ~CRTSCTS;

	tty_opts.c_cflag |= CREAD | CLOCAL;  // turn on READ & ignore ctrl lines
	tty_opts.c_iflag &= ~(IXON | IXOFF | IXANY); // turn off s/w flow ctrl

	tty_opts.c_lflag &= ~(ICANON | ECHO | ECHOE | ISIG); // make raw
	tty_opts.c_oflag &= ~OPOST; // make raw

	// see: http://unixwiz.net/techtips/termios-vmin-vtime.html
	tty_opts.c_cc[VMIN]  = 0;
	tty_opts.c_cc[VTIME] = 0;
	//end3

	foo=tcsetattr(tty,TCSANOW, &tty_opts);
	if(foo<0) return -4;
	
	return 0;
}

int tty_test_connection(int tty)
{
	int foo;
	char buf[4]={'p',0,0,0};
	
	foo=write(tty,buf,1);
	if(foo<0){
		perror("write");
		return foo;
	}
	if(foo==0){
		puts("nothing written");
		return foo;
	}
L0:
	foo=read(tty,buf,2); //mc should return 2 bytes p and \0
	if(foo<0){
		perror("read");
		return foo;
	}
	if(foo<2){
		puts("less then 2 bytes was red");
		return foo;
	}

	buf[foo]='\0';
	printf("ping was: %s\n",buf);
	return foo;
}

int main(int ac,char *av[])
{
	int tty_dev;
	int foo;
	
	tty_dev=0;
	tty_dev = open("/dev/ttyUSB0", O_RDWR | O_NOCTTY | O_NDELAY);
	if(tty_dev < 0){
		perror("open");
		return -1;
	}
	puts("open: ok");
	
	foo=tty_set(tty_dev);
	if(foo<0){
		perror("tty_set");
		close(tty_dev);
		return -1;
	}
	puts("tty_set: ok");
	
	
	foo=tty_test_connection(tty_dev);
	if(foo<0){
		perror("tty_test_connection");
		printf("foo: %d\n",foo);
		return -1;
	}
	printf("tty_test_connection: %d characters red\n",foo);
	close(tty_dev);
	return 0;
}

int tty_test_connection(int tty)
{
	int foo;
	char buf[4]={'p',0,0,0};
	
	struct pollfd descriptor;
	memset(&descriptor,0,sizeof(struct pollfd));
	
	foo=write(tty,buf,1);
	if(foo<0){
		perror("write");
		return foo;
	}
	if(foo==0){
		puts("nothing written");
		return foo;
	}

L0:
	descriptor.fd=tty;
	descriptor.events = POLLIN;
	foo=poll(&descriptor,1,2000);
	if(foo<0){
		perror("poll");
		return foo;
	}
	if(foo==0){
		puts("poll timeout");
		goto L0;
	}
	if(descriptor.revents && POLLIN == POLLIN){
		foo=read(tty,buf,4);
		if(foo<0){
			perror("read");
			return foo;
		}
	} else {
		puts("no POLLIN in revents");
		return 0;
	}
	
	buf[foo]='\0';
	printf("ping was: %s\n",buf);
	return foo;
}