/*
 * heatbeats.c -- sends heartbeats (pulses) over a serial port with RTS and DTR
 * This Program needs to be restarted (= killed and new started) within MAXUPTIME Seconds; otherwise the watchdogs resets!
 * 2001
 */

#include <stdio.h>
#include <sys/io.h>        /* or asm/io.h; for inb, ioperm, iopl  ... */
#include <stdlib.h>        /* atoi */
#include <unistd.h>     // getuid()
#include <errno.h>      // EPERM
#include <time.h>	// time 

#define MAXUPTIME 1000000 // default 1 Ms : 1 1/2 Weeks

int main(int argc, char **argv)
{
  const int udelay = 2000000;	// 2 s delay
  const unsigned int sbase=0x2f8; // 0x2f8 usually for the second serial port, 0x3f8 for first,  0x3E8 for third, 0x2E8 for fouth
  unsigned char s0=0, s1=1, sregister=0;	// status register values of the serial port
  int starttime=0;		// starttime

  if (geteuid()!=0)
  {
    printf("\a\n\nError: $EUID==%d!=0 (you are not a superuser).\n\n",getuid());
    exit (-EPERM);
  }
  starttime = time(NULL);
  iopl(3); /* unlimited I/O access permission, nessesary above the 0x3ff limit e. g. at 0x9800=38912 */
  nice(19); /* be nice ;-) */
  sregister = inb(sbase+4);
  s0 = sregister & 0xfc; // clear RTS and DTR
  s1 = sregister | 0x03; // set RTS and DTR
  while ( time(NULL) - starttime < MAXUPTIME ) // while system is running and uptimelimit is not reached
  {
    outb(s0,sbase+4);	// first part of the heartbeat
    usleep(udelay);	// sleep
    outb(s1,sbase+4);	// second part of the heartbeat
    usleep(udelay);	// sleep
  }
  iopl(0); /* no I/O permission */
  exit(-1); /* never happen within uptime */
}