#include <stdio.h>	
#include <string.h>	
#include <unistd.h>	
#include <fcntl.h>	
#include <termios.h>	
#include <errno.h>	
#include <sys/select.h>	
#include <stdlib.h>	//
#include <sys/types.h>	//

#define BAUDRATE B9600	//Baud rate set to 9600 bit/sec
#define SERIALDEVICE "/dev/ttyS0"	//Serial port to be used for communication

int main(int argc, char *argv[]){
	int sfd, ret, i;
	struct termios oldtio, newtio;
	char buf[256];
	char buf1[256];
	fd_set	readfds;	//file descripto set
	int maxfd;		//maximum file descriptor used
	long disable;

	//open serial port to be non-blocking
	sfd = open(SERIALDEVICE, O_RDWR );//| O_NOCTTY | O_NONBLOCK);//change later pg(241)
	if( sfd < 0 ){
		perror(SERIALDEVICE);
		exit(1);	
	}
	//current maximum file descriptor
	maxfd = sfd + 1;

	//struct newtio for new serial  port setting
	bzero(&newtio,sizeof(newtio));
	
	//struct oldtio for holding the original port setting
	bzero(&oldtio,sizeof(oldtio));

	//save current options for the port 
	tcgetattr(sfd,&oldtio);

	/*---set the baudrate---*/
	//set the input speed
	cfsetispeed(&newtio, BAUDRATE);
	//set the output speed
	cfsetospeed(&newtio, BAUDRATE);

	/*---new port setting---*/
	//enable receiver and set local mode
	newtio.c_cflag |= (CLOCAL | CREAD);
	

/*Setting Raw Terminal I/O*/
	//select 8 data bits, no parity and 1 stop bit
	newtio.c_cflag &= ~PARENB;
	newtio.c_cflag &= ~CSTOPB;	
	newtio.c_cflag &= ~CSIZE;	//Mask the character size bits
	newtio.c_cflag |= CS8;		//select 8 data bits	

 
	//Clear ISTRIP to get all eight bits also clear clear parity checking
	//clear IEXTEN to turn off extended character processing
	//no flow contro clear IXON
	//clear BRKINT 
	newtio.c_iflag &= ~(INLCR | ICRNL | ISTRIP | INPCK | IXON | BRKINT);
	
	//clear OPOST to turn off output processing
	newtio.c_oflag &= ~OPOST;

	//clear ECHO and set MIN and TIME.
	//clear ISIG	
	newtio.c_lflag &=~(ICANON | ECHO | IEXTEN | ISIG);


	for (i = 0; i < NCCS; i++)		//NCCS
		newtio.c_cc[i] = (cc_t)disable;		//what is this?
		newtio.c_cc[VMIN] = 1;
		newtio.c_cc[VTIME] = 0;
	


	tcflush(sfd, TCIFLUSH);
	ret = tcsetattr(sfd, TCSANOW, &newtio);
	if (ret < 0){
		perror("Failure to set new port options\n");
		exit(1);
	}

	/*---loop for reading from the port---*/

	FD_ZERO(&readfds);
	while(1){
		FD_SET(sfd, &readfds);
		FD_SET(0, &readfds);
		ret = select(maxfd, &readfds, NULL, NULL, NULL);	
		if (ret < 0){
			perror("select failure\n");
			exit(1);		
		}	
		//check for calling file descriptor
		if ( FD_ISSET(sfd, &readfds)){
			//handle input from the serial port
			bzero(buf1,sizeof(buf1));
			ret = read(sfd, buf1, sizeof(buf1));
			if(ret < 0){
				perror("failure to read serial port\n");
				exit(1);			
			}
			printf("Contents from serial input : %s\n", buf1);

		}else{
			//read input from keyboard
			bzero(buf,sizeof(buf));
			fgets(buf, sizeof(buf), stdin);
			if (strncmp("quit", buf, 4)==0 ){
				//prepare to close serial port
				printf("now closing serial port\n");
				//restore old port setting before closing port
				tcsetattr(sfd, TCSANOW, &oldtio);
				close(sfd);
				  return 0;		
		}else{//may be try writting the serial port
	
		
		}	
	
		}
	}




	
  }