#!/usr/bin/perl
#
# Usage: fetch_temperature [outfile]
#
# Nice data fetch script for arduino temperature sensor
#
# If you call it without arguments, it prints the current temperature to the
# console.
#
# If you pass a filename as argument, it adds the current date, time and temperature
# to the end of the file

use strict;
use warnings;

# Set up the serial port
use Device::SerialPort;
my $port = Device::SerialPort->new("/dev/ttyUSB0");

# Some simple error catch mechanism
if(!$port) {
	my $port = Device::SerialPort->new("/dev/ttyUSB1");
}

# If no connection could be made, quit
if(!$port) {
			print "No device found!!\n";
			exit 1;
}

# Initialize communication
# # 38400, 81N on the USB ftdi driver
$port->baudrate(38400);
$port->databits(8);
$port->parity("none");
$port->stopbits(1);

# Some initialization
my $filename = "";
$filename = shift;

# Create nice timestamp YYYY-MM-DD HH:MM:SS for file output
my ($sec,$min,$hour,$mday,$mon,$year,$wday,$yday,$isdst)=localtime(time);
my $timestamp = sprintf "%4d-%02d-%02d %02d:%02d:%02d",
$year+1900,$mon+1,$mday,$hour,$min,$sec;

my $temp = "";

my $starttime = time(); 
my $written = 0;

# Loop while there is no data available
while (!$temp) {
	
	# If we didn't send anything yet, send signal (a simple '1') to the arduino
	if(!$written) {	
		$port->write(1);
		$written = 1;
	}

	# Poll to see if any data is coming in
	$temp = $port->lookfor();

	# If there was too much time spent, quit the loop and set error message as result
	if(time() > $starttime + 5) {
		$temp = "Sensor not yet ready!";
	}
}

# If a filename has been passed as argument, write the result into this file
if($filename) {
# Write down temp into file with current timestamp
open FILE, ">>$filename" or die "could not open $filename: $!\n";
print FILE "$timestamp $temp\n";
close FILE;
}
# else print the result to the console
else {
	print "$temp\n";
}

# goodbye