use Fcntl qw/:DEFAULT/;
use IO::Termios ();
use IO::Stty ();

sysopen my $fh, '/dev/ttyUSB0', O_RDWR or die "sysopen: $!";
my $handle = IO::Termios->new($fh) or die "IO::Termios->new: $!";
$handle->set_mode('300,7,e,1');
IO::Stty::stty($handle, qw/ raw -parodd cs7 -cstopb parenb -ixoff -crtscts -hupcl -ixon -opost -onlcr -isig -icanon -iexten -echo -echoe -echoctl -echoke/);

my $raw = "\x2F\x3F\x21\x0D\x0A";
$handle->syswrite($raw) == length($raw) or die "syswrite";
my $raw = "\x06\x30\x30\x30\x0D\x0A";
$handle->syswrite($raw) == length($raw) or die "syswrite";

for (1..300) {
    my $toread = 1;
    $handle->sysread(my $in, $toread)
        == $toread or die "sysread";
    print $in;
}

$handle->close;

##</code><code>##

/?!
000
/LOG4LK13BD202015