#!/usr/bin/perl
use strict;
use warnings;
use Win32::SerialPort;

my $kSTX = "\x02";
my $kETX = "\x03";

my $obj = bless { port => Win32::SerialPort->new('COM1'), idle => 1 };

$obj->configurePort();

while (1) {
    my $crc = $obj->readSerialPort();

    next if !defined $crc;

    print $obj->{buffer};
} continue {
    sleep 1;
}

sub configurePort {
    my ($self) = @_;

    $self->{port}->...;
}

sub writeSerialPort {
    my ( $self, $outStr ) = @_;

    $self->{port}->write($outStr) || die "Serial port write failed: $!\n";
}

sub readSerialPort {
    my ($self) = @_;

    while ( my $byte = $self->{port}->input() ) {
        next if $self->{idle} && $byte eq $kSTX;

        if ( $byte eq $kSTX ) {
            $self->{buffer} = '';
            $self->{idle}   = undef;
            next;
        }

        if ( $byte ne $kETX && 80 > length $self->{buffer} ) {
            $self->{buffer} .= $byte;
            next;
        }

        # Got end of record
        my $crc = 0;

        $crc += ord($_) for split '', $self->{buffer};
        $crc &= 0xFF;
        $self->{idle} = 1;
        return $crc;
    }

    return;
}