Low-tech door monitoring with ICQ

Submitted by zany on Wed, 2009-02-18 16:38

Do you want to monitor some door? Get notified when it opens/closes? This is low-tech solution for the trusty old parallel port.

Just solder a Reed-switch and protective resistor to a DB-25 connector. Then run this simple program as daemon to monitor the switch.
(This project is about 10 years old. You might consider fancy things like DBUS today...)

I my case the program runs scripts which controls the status of a running ICQ client. The door in question is the front door of our club room. Yeah!

  1. #include <stdio.h>
  2. #include <unistd.h> /* needed for ioperm() */
  3. #include <asm/io.h> /* for outb() and inb() */
  4. #include <fcntl.h>
  5.  
  6. #define DATA 0x378
  7. #define STATUS DATA+1
  8. #define CONTROL DATA+2
  9.  
  10. #define LP_PE 0x04 /* shifted */
  11.  
  12. int runscript(char *cmd)
  13. {
  14.     int ret;
  15.  
  16.     if((ret=fork())==-1) { perror("Fork Failed"); return 1; }
  17.  
  18.     if(ret==0) // child 
  19.     {
  20.         char *args[] = { NULL };
  21.         execve(cmd, args, NULL);
  22.         perror("Exec Failed"); return 1;
  23.     }
  24.  
  25.     wait(&ret);  // wait for child
  26.     return 0;
  27. }
  28.  
  29. int main(void)
  30. {       
  31.     int v, v0;
  32.  
  33.     if (ioperm(DATA,3,1))
  34.     {
  35.         printf("Sorry, you were not able to gain access to the ports\n");
  36.         printf("You must be root to run this program\n");
  37.         exit(1);
  38.     }
  39.  
  40.     for (;;) {
  41.  
  42.         v = ((inb(STATUS)^0x80) >> 3);
  43.  
  44.         if (v != v0)
  45.             if ((v & LP_PE) != 0)
  46.             {
  47.                 //printf("Status: opening\n");
  48.                 runscript("/root/bin/opendoor");
  49.             }
  50.             else
  51.             {
  52.                 //printf("Status: closing\n");
  53.                 runscript("/root/bin/closedoor");
  54.             }
  55.         v0 = v;
  56.  
  57.         sleep(1);
  58.         //usleep(100000);
  59.  
  60.     }
  61.  
  62.     return 0;
  63. }

The script should run some commands (also consider dropping the privileges) but must not stay in the foreground (i.e. needs to terminate). Simple example:

  1. #!/bin/sh
  2. exec su someuser -l -c /usr/local/bin/opendoor-user

Where opendoor-user would set the status in licq, micq, pidgin, ...

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