use strict;
use Device::SerialPort;
my $port = Device::SerialPort->new("/dev/ttyUSB0");

$port->baudrate(9600); # Configure this to match your device
$port->databits(8);
$port->parity("none");
$port->stopbits(1);
$port->read_const_time(1000);

while (1) {
    $port->write("P");
    my ($count, $data) = $port->read(1);
    if ($count == 1) {
        my $value = unpack("C", $data) - 45;
        print "temp = $value\n";
    }
    else {
        print "timeout\n";
    }

    $port->write("U");
    ($count, $data) = $port->read(2);
    if ($count == 2) {
        my $value = unpack("n", $data);
        print "dist = $value\n";
    }
    else {
        print "timeout\n";
    }
}