fmscan.c

   1 /* scan.c - v4l radio band scanner using signal strength
   2
   3    Copyright (C) 1999  Russell Kroll <rkroll@exploits.org>
   4
   5    This program is free software; you can redistribute it and/or modify
   6    it under the terms of the GNU General Public License as published by
   7    the Free Software Foundation; either version 2 of the License, or
   8    (at your option) any later version.
   9
  10    This program is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13    GNU General Public License for more details.
  14
  15    You should have received a copy of the GNU General Public License
  16    along with this program; if not, write to the Free Software
  17    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  18  */
  19
  20 #include <math.h>
  21 #include <stdio.h>
  22 #include <fcntl.h>
  23 #include <stdlib.h>
  24 #include <unistd.h>
  25 #include <string.h>
  26 #include <asm/types.h>
  27 #include <sys/ioctl.h>
  28 #include <linux/videodev.h>
  29
  30 void help (char *prog)
  31 {
  32         printf ("usage: %s [-h] [-s <freq>] [-e <freq>] [-i <freq>]\n\n", prog);
  33
  34         printf ("-h        - display this help\n");
  35         printf ("-s <freq> - set start of scanning range to <freq>\n");
  36         printf ("-e <freq> - set end of scanning range to <freq>\n");
  37         printf ("-i <freq> - set increment value between channels to <freq>\n");
  38         printf ("<freq>    - a value in the format nnn.nn (MHz)\n");
  39
  40         exit (1);
  41 }
  42
  43 int main(int argc, char **argv)
  44 {
  45         int     fd, ret, i, tries = 25;
  46         struct  video_tuner vt;
  47         float   perc, begval, incval, endval;
  48         long    lowf, highf, freq, totsig, incr, fact;
  49         char    *progname;
  50
  51         progname = argv[0];     /* getopt munges argv[] later */
  52
  53         fd = open ("/dev/radio0", O_RDONLY);
  54         if (fd == -1) {
  55                 perror ("Unable to open /dev/radio0");
  56                 exit (1);
  57         }
  58
  59         /* USA defaults */
  60         begval = 87.9;          /* start at 87.9 MHz */
  61         incval = 0.20;          /* increment 0.2 MHz */
  62         endval = 107.9;         /* stop at 107.9 MHz */
  63
  64         while ((i = getopt(argc, argv, "+e:hi:s:")) != EOF) {
  65                 switch (i) {
  66                         case 'e':
  67                                 endval = atof (optarg);
  68                                 break;
  69                         case 'i':
  70                                 incval = atof (optarg);
  71                                 break;
  72                         case 's':
  73                                 begval = atof (optarg);
  74                                 break;
  75                         case 'h':
  76                         default:
  77                                 help(progname);
  78                                 break;
  79                 }
  80         }
  81
  82         vt.tuner = 0;
  83         ret = ioctl(fd, VIDIOCGTUNER, &vt);     /* get initial info */
  84
  85         if ((vt.flags & VIDEO_TUNER_LOW) == 0)
  86                 fact = 16;
  87         else
  88                 fact = 16000;
  89
  90         /* cope with bizarre things from atof() like 95.099998 */
  91         lowf = fact * (ceil(rint(begval * 10)) / 10);
  92         highf = fact * (ceil(rint(endval * 10)) / 10);
  93
  94         incr = fact * incval;
  95
  96         printf ("Scanning range: %2.1f - %2.1f MHz (%2.1f MHz increments)...\n",
  97                 begval, endval, incval);
  98
  99         for (freq = lowf; freq <= highf; freq += incr) {
 100                 ioctl (fd, VIDIOCSFREQ, &freq);         /* tune */
 101
 102                 printf ("%2.1f: checking\r", (freq / (double) fact));
 103
 104                 fflush (stdout);
 105                 usleep (400000);                /* let it lock on */
 106
 107                 totsig = 0;
 108                 for (i = 0; i < tries; i++) {
 109                         vt.tuner = 0;
 110                         ret = ioctl(fd, VIDIOCGTUNER, &vt);     /* get info */
 111                         totsig += vt.signal;
 112                         fflush(stdout);
 113                         usleep (15000);
 114                 }
 115
 116                 /* clean up the display */
 117                 printf ("                  \r");
 118
 119                 perc = (totsig / (65535.0 * tries));
 120
 121                 if (perc > .5)
 122                         printf ("%2.1f: %3.1f%%          \n",
 123                                 (freq / (double) fact), perc * 100.0);
 124         }
 125
 126         close (fd);
 127
 128         return (0);
 129 }