ee

#!/usr/bin/perl

use strict;

# chip => { #_of_args => [[qw/Inputs Outputs/], sub { calculation }]}
my %expr = (
  parallel_res => { '*' => [[qw/R/], sub { my $tmp = 0; map { $tmp += (1/$_) } @_; 1/$tmp } ]},
  #series_res   => { '*' => [[qw/R/], sub { my $tmp = 0; map { $tmp += (1/$_) } @_; return 1/$tmp } ]},
  bat_j => {
    2 => [ [qw/V Ah J/],
      sub { $_[1] * $_[0] * 3600 } ]},
  bat_wh => {
    2 => [ [qw/V Ah Wh/],
      sub { $_[1] * $_[0] } ]},
  cap_wh => {
    2 => [ [qw/V Farad Wh/],
      sub { 1/2 * $_[1] * $_[0] ** 2 / 3600 } ]},
  cap_j => {
    2 => [ [qw/V Farad J/],
      sub { 1/2 * $_[1] * $_[0] ** 2 } ]},
  voltage_div => {
    3 => [ [qw/Vin R1 R2 Vout/],
      sub { $_[0] * ($_[2] / ($_[1] + $_[2])) } ]},
  lm317 => {
    2 => [ [qw/R1 R2 Voltage/],
      sub { 1.25 * ($_[1] / $_[0] + 1) }],
    1 => [ [qw/Voltage R1 R2/],
      sub { (240, ($_[0] / 1.25 - 1) * 240) }],
  },
  esr => {
    2 => [ [ qw/SignalV VDiff ESR/], sub { (($_[1] * 50) / ($_[0] - $_[1])) } ],
    3 => [ [ qw/SignalV VDiff InlineRes ESR/], sub { (($_[1] * $_[2]) / ($_[0] - $_[1])) } ],
  },
  _uf => { 1 => [ [qw/uF nF pF/], sub { ($_[0] * 1e3, $_[0] * 1e6) } ] },
  _nf => { 1 => [ [qw/nF uF pF/], sub { ($_[0] / 1e3, $_[0] * 1e3) } ] },
  _pf => { 1 => [ [qw/pF uF nF/], sub { ($_[0] / 1e6, $_[0] / 1e3) } ] },
);

# get function, conversion, args
my ($fn, $conv, @args) = handle_args(@ARGV);

sub handle_args
{
  my $conv = lc shift;
  my ($end) = ($conv =~ /([a-z]+)$/i);
  if ($expr{"_$end"})
  {
    $conv =~ s/^(.*)$end/_$end/;
    unshift(@_, $1);
  }

  my @args;
  foreach my $arg (@_)
  {
    push @args, ($arg =~ /^(.*)x(\d+)$/ ? ($1) x $2 : $arg);
  }

  my $fn = $expr{$conv}{@args} || $expr{$conv}{'*'};
  return ($fn, $conv, @args);
}

usage() if !$fn;
my ($txt, $sub) = @{$fn};
push @args, &$sub(@args);
foreach my $i (0 .. $#args)
{
  # conversion or calculate
  print ($conv =~ /^_/ ? "$args[$i]$txt->[$i]\n" : $txt->[$i] . ": $args[$i]\n");
}
exit;

sub usage
{

  die "usage: $0 <arg> [opts]

XuF                 # converts 'X'uF to nF/pF
bat_wh V            # get watt-hours from battery
bat_j V Ah          # get joules from battery
cap_wh V Farad      # get watt-hours of capacitor
cap_j V Farad       # get joules from capacitor
voltage_div V R1 R2 # get voltage from voltage divider (R2 to gnd)
parallel_res R1 R2  # get total resistance of parallel resistors
series_res R1 R2    # get total resistance of series resistors
lm317 V             # calculate R1 and R2 to produce voltage
lm317 R1 R2         # voltage created from R1 and R2
esr V VDiff [Res]   # calculate ESR of cap given V signal and VDiff when AC coupled (Res=50)
";

}
=cut

# LM217/LM317 adjustable voltage regulator
if ($arg eq 'lm317' && @ARGV == 1)
{
  my $v = shift;
  my $r1 = 240;
  my $r2 = ($v / 1.25 - 1) * $r1;
  print "R1: $r1\nR2: $r2\nVoltage: ${v}V\n";
}
elsif ($arg eq 'lm317' && @ARGV == 2)
{
  my ($r1, $r2) = @ARGV;
  my $v = 1.25 * ($r2 / $r1 + 1);
  print "R1: $r1\nR2: $r2\nVoltage: ${v}V\n";
}
elsif ($arg =~ /^(\d+|\d*\.\d+|\d+\.\d*)(u|n|p)?f$/i)
{
  my ($num, $unp) = ($1, lc($2));
  my $uf;
  $uf = $num/1e3 if $unp eq "n";
  $uf = $num/1e6 if $unp eq "p";
  my $nf = $uf * 1000;
  my $pf = $nf * 1000;
  print "${uf}uF\n";
  print "${nf}nF\n";
  print "${pf}pF\n";
}
else
{
  usage();
}