#!/bin/perl

use strict;
use warnings;

my $strToSend = "\xfe\x04\x01";
my $CRC16 = GetCRC16($strToSend. "\x00\x00"); # ergibt "BED2"
print "Checksum 1: ". sprintf("%X", $CRC16). "\n";


my $strReceived = "\xfe\x04\x01\xbe\xd2";
$CRC16 = GetCRC16($strReceived); # ergibt 0
print "Checksum 2: ". sprintf("%X", $CRC16). "\n";

sub GetCRC16 {
    my $s = shift;
    
    my $CRCreg = 0xffff00;
    
    for (my $cp=0; $cp<length($s); $cp++) {
    $CRCreg |= ord( substr($s,$cp,1) );
    
    for (my $bp=0; $bp<8; $bp++) {
        $CRCreg <<= 1;
        if ($CRCreg & 0x1000000) { 
        $CRCreg ^= 0x100200; # hier ist das Polynom 0x1002 enthalten
        }
        $CRCreg &= 0xffffff;
    }
    }
    return $CRCreg >> 8;
} 

1;