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

int config_serial(char * device, unsigned int baudrate){
    struct termios options;
    int fd;
    
    fd = open(device, O_RDWR | O_NOCTTY | O_NDELAY );
    if (fd < 0)
    {
        /*
        * Could not open the port.
        */
      
        perror("config_serial: Não pode abrir a serial - ");
        return -1;
    }

    fcntl(fd, F_SETFL, 0);

    /*
    * Get the current options for the port...
    */
    tcgetattr(fd, &options);
    
    /* sets the terminal to something like the "raw" mode */
    cfmakeraw(&options);
    
    /*
    * Set the baudrate...
    */
    cfsetispeed(&options, baudrate);
    cfsetospeed(&options, baudrate);

    /*
    * Enable the receiver and set local mode...
    */
    options.c_cflag |= (CLOCAL | CREAD);
    
    /*
     * No parit, 1 stop bit, size 8
     */
    options.c_cflag &= ~PARENB;
    options.c_cflag &= ~CSTOPB;
    options.c_cflag &= ~CSIZE;
    options.c_cflag |= CS8;

    
    /*
     * Clear old settings
     */
    options.c_cflag &= ~CRTSCTS;
    options.c_iflag &= ~(IXON | IXOFF | IXANY);
    
    /* non-caninical mode */
    options.c_lflag &= ~ICANON; 

    /*
    * Set the new options for the port...
    */
    tcsetattr(fd, TCSANOW, &options);
    
    /* configura a tty para escritas e leituras não bloqueantes */
    //fcntl(fd, F_SETFL, fcntl(fd, F_GETFL) | O_NONBLOCK);
    
    return fd;
}


int main(int argc, char** argv){
	int fd;
	char a;
	
	if(argc<2){
		printf("Usage: ./serial <char>");
		return 0;
	}
	
	fd = config_serial("/dev/ttyAMA0", B9600);
	if(fd<0){
		return 0;
	}
	
	a = argv[1][0];
	
	write(fd, &a, 1); 
	
	read(fd, &a, 1);
	
	printf("%c\n", a);
	
	close(fd);
		
	return 0;
}