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

#define BAUDRATE B9600
#define MODEMDEVICE "/dev/ttyUSB0"
#define _POSIX_SOURCE 1 /* POSIX compliant source */

int main()
{
    int fd, res;
    struct termios oldtio, newtio;
    char buf[255];

    // Open the serial port
    fd = open(MODEMDEVICE, O_RDWR | O_NOCTTY);
    if (fd < 0)
    {
        perror(MODEMDEVICE);
        exit(1);
    }

    // Save current port settings
    tcgetattr(fd, &oldtio);

    // Set new port settings
    memset(&newtio, 0, sizeof(newtio));
    newtio.c_cflag = BAUDRATE | CS8 | CLOCAL | CREAD;
    newtio.c_iflag = IGNPAR;
    newtio.c_oflag = 0;

    // Set input mode to non-canonical
    newtio.c_lflag = 0;

    // Set timeouts to 0.1 seconds
    newtio.c_cc[VTIME] = 1;
    newtio.c_cc[VMIN] = 0;

    // Apply new settings
    tcflush(fd, TCIFLUSH);
    tcsetattr(fd, TCSANOW, &newtio);

    // Send data
    char data[] = "Hey, it's Eden\n";
    write(fd, data, strlen(data));

    // Read response
    while (1)
    {
        res = read(fd, buf, sizeof(buf));
        if (res > 0)
        {
            buf[res] = 0;
            printf("Received response: %s", buf);
            break;
        }
    }

    // Restore old port settings and close serial port
    tcsetattr(fd, TCSANOW, &oldtio);
    close(fd);

    return 0;
}