ts3_remote_ham/ptt_daemon.c

#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <termios.h>
#include <fcntl.h>
#include <sys/ioctl.h>

int main(int argc, char **argv)
{  

  if (argc < 2) {
    fprintf(stderr, "Usage: ./ptt_daemon <device> <1 or 0 (RTS high or low)>\n");
    exit(1);
  }

  int fd = open(argv[1], O_RDWR | O_NDELAY);
  if (fd < 0) {
    exit(1);
  }

  int rtsEnable;
  sscanf(argv[2], "%d", &rtsEnable);

  int flags;
  ioctl(fd, TIOCMGET, &flags);

  // The below flags can be replaced by TIOCM_DTR to use the DTR line instead, See $ man "TIOCMSET(2const)"
  if (rtsEnable != 0) {
    flags |= TIOCM_RTS; // brings the RTS line high
  } else {
    flags &= ~TIOCM_RTS;
	}

  ioctl(fd, TIOCMSET, &flags);

  close(fd);

}