scripts/rcf at master · jzu/scripts · GitHub

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
#!/usr/bin/perl -w

# RCF.pl - jzu@free.fr 2010 - WTFPL
# Computes the third value of a first-order RC filter, given two of them
# Example: 0.000001 Farad (1u) and 1000 Ohm (1k) give about 159 (Hz)

use strict;


my %h = ("-12" => "p",  # pico
         "-9"  => "n",  # nano
         "-6"  => "u",  # micro
         "-3"  => "m",  # milli
         "0"   => "",   #
         "3"   => "k",  # kilo
         "6"   => "M"   # mega
        );


# Function expansion
# Takes a number + optional 10^3 multiplier (Mkmunp)
# Issues a float

sub expansion($) {

  my $value = shift;
  my $unit;

  ($value =~ m/[0-9]$/) and
    return $value;

  $unit = $value;
  $unit =~ s/.*(.)$/$1/;
  chop $value;

  ($unit eq 'M') and $value *= 1000000;
  ($unit eq 'k') and $value *= 1000;
  ($unit eq 'm') and $value /= 1000;
  ($unit eq 'u') and $value /= 1000000;
  ($unit eq 'n') and $value /= 1000000000;
  ($unit eq 'p') and $value /= 1000000000000;

  return $value;
}


# Function fmt
# Takes a float on input
# Issues a rounded number (2 significant digits) + multiplier (Mkmunp)

sub fmt ($) {

  my $value = shift;

  my ($sci, $rnd, $norm, $i, $j);

  # First, determine the magnitude of the number

  for ($i = 6; $i > -13; $i--) {
    if (int ($value / (10**$i)) > 0) {
      $sci = sprintf ("%.1f*10**$i", $value / (10**$i));
      last;
    }
  }
  $rnd = eval $sci;

  # Then, round the number accordingly, and prepare for 10^3 multipliers

  for ($j = 6; $j > -13; $j -= 3) {
    if (int ($rnd / (10**$j)) > 0) {
      if ($i % 3 == 0) {
        $norm = sprintf ("%.1f%s", $rnd/(10**$j), $h{$j});
      }
      else {
        $norm = sprintf ("%.0f%s", $rnd/(10**$j), $h{$j});
      }
    return $norm;
    }
  }
}


# Main code : F=1/(2PiRC), R=1/(2PiFC), C=1/(2PiRF)

if ((defined $ARGV [0]) and
    (defined $ARGV [1]) and
    ($ARGV [0] =~ /^(\d+\.?\d*|\.\d+)[Mkmunp]?$/) and
    ($ARGV [1] =~ /^(\d+\.?\d*|\.\d+)[Mkmunp]?$/)) {

  my $result = 1 / (6.283 * expansion ($ARGV [0]) * expansion ($ARGV [1]));

  print $result . " (" .  fmt ($result) . ")\n";

  exit 0;
}

print STDERR "Usage: rcf num[Mkmunp] num[Mkmunp] \n";