Perl and anything else

Finally starting to get somewhere with the weather station stats

This post is really just a record of what I've done to get to the point of graphing and displaying the weather info from my weather station.

The weather stations reciever and display panel is hooked up via USB to the mediacentre, my MythTV box that never gets turned off.

I've finally written a working script captures the data and writes to the RRD database, however all of this sits on the mediacentre.  My web stuff sits on my linux server in a cupboard.

To get access to the database for the web page to come, I've had to think about the implimentation somewhat and have come up with the following:

On the mediacentre I have created an rrd directory under /var/local

Under that I'm going to create a directory structure based on the RRD databases I may have, so for the weather station, I now have weather, below that logs, which is where all the text based logs will be stored for later processing should I need some historical data, or just want to do something different.

I have exported /var/local/rrd and mounted it via nfs on the Linux server.

All I need to do now is write the code to generate the web page.

Steps to installing all requirements on a debian based distro

The perl script I'm going to use to read the weather stations data logger ( reciever ), uses the Device::USB module.

To get to the point of installing this module on a "clean" system somethings need to be installed.

To build the required binaries, we'll need to install the build-essential package, we'll also need the libusb-dev package:

<code>

apt-get install build-essential

apt-get install libusb-dev

</code>

To build the Device::USB module there are dependancies that need to be met, once local::lib has been installed it's just a matter of using the cpan client to install:

Inline::MakeMaker

and

Device::USB

That should be it.

Just a note with the udev rules.  The example I followed was using deprecated terms for the device event and attributes.

My udev rule for the weatherstion is:

<code>

SUBSYSTEMS=="usb", ATTRS{idVendor}=="1941", ATTRS{idProduct}=="8021", GROUP="weather-station", MODE="0660"

</code>

One other thing, when setting these things up using "screen", exit all the way out and re-login.  This actually fixed the problem of the script not being able to connect to the usb device.

That's it for now, the laptop is about to run out of battery and I can run the script to read the data back. Next up we'll look at what is coming out of the updated script.

First steps to capturing weather data from the reciever.

Having finally got my weather station home, I ended up googling around to find out what, if anything was out there that would allow me to hook up the receiver via USB to a linux computer to start capturing all the data.

It was good to see that it wasn't going to be impossible, I found solutions in C and Python and much to my surprise, Perl!

Of course the perl option is going to be the one I'll go with first.  I've grabbed the latest version of the data logger from here.

I had found this page some time around october/november 2010 and just as I was starting to get back into getting the data capturing sorted out again the web site went offline.  Thankfully it's back for this attempt at getting the data.

To capture the data 24/7 I need a computer that obviously doesn't get turned off.  Given the cost of electricity these days it's a hard argument to make to turn on a dedicated computer just to capture the data.

However, in this house, there is one computer that meets this requirement, the MythTV backend.

To do what I need I'll need to install a number of perl modules not likely to be included in the mythbuntu distribution ( which runs the MythTV box ).

To facilitate this, I'm using the excellent local::lib.  I'll boot strap the environmet following the instructions in the pod.

After my last attempt at capturing the data, I found that you need a udev rule to allow permission to the USB device with out running as root.  Again googling brought me tothis page. 

So a new udev rule is in order.

That's it for now.  A quick update iwth what I'm doing with some links.

 

Lets get started with the weatherstation

As I said in my blog reboot entry, this is where I'm going to cover things I'm doing personally rather than dedicated to Padre, the Perl IDE.

I'm still a perlwannabe at heart, so the blog names still fits.  :)

The story of the weather station starts many, many years ago.  As with all things I like to have a reason to do something so that I actually get around to do it.  I think this is normal so personally never hold myself accountable for not getting much done.. no reason, no reason to get it done.  :)

Anyway, at the time I figured that learning C would be a good thing, but knowing that once you get past the "hello world" example, you generally end up with the classic "CD database" to push you to the next level.

Neither of these are compelling enough to learn C, however, making your <insert device> work with linux is certainly one reason to learn a programming language, especially one that is as low level as C.

I think there's an inherant desire in most males to know things about their environment, and weather is certainly a big part of it.  I mentioned this one time while on a project that I thought it would be cool to have a weather station, interface the rs232 (serial) port to a linux server and dump the sensor data into a database.  Of course that would mean a web page with charts and all sorts of cool reasons to hack things.

Way back then, I wasn't earning alot and household income, with two young kids, wasn't something that would allow such an extravagence.

So I shelved the idea, with it every now and then popping up on "slow" days.

Over the years, as with all things technologywise, hardware gets cheaper, interfaces change and if you're lucky you have a little more cash to spend on yourself.

Given that one of the guys I was working with at the time I first mentioned my desire to have weather station paid out over $1000 for a rather nice Davis weather station ( I'm pretty sure it was ), I flicked through the jaycar catalogue and found their $150 "digitec" weather station was on special, for something like $99.

OMG!  $99 for a weather station.. and it was wireless!!! and even better USB!!!!

So I figured for $99 I'd just go with what I got and google my way around finding something that allowed me to hook it up to a linux computer.  Even more enticing was that during a long break between contracts, I discovered the Arduino and somehow discovered that one of the projects in a book just on the market covered creating a board that listened into the transmissions from weatherstations and allowed you to grab the data. 

It was like a perfect storm of reasoning that I felt that the $99 was worth the risk.  So I got myself my first ever weather station.

It turns out the digitech weather station is a rebranded Fine Offset WH-1080.  Once I knew this, googling for this to find code etc was simple.

But that's for another day.

The weather station sat on the floor for ages as I agonised over where to put.  Should I put it on the TV antenna mast high above the house (making it interesting come time to change the batteries) or someplace more accessable, while accepting that wind direction and speed may be effected.

In the end I just stuck it to the swing chair out the back of the yard just to put it outside and see if the base station ( the LCD screen ) could pick up the signal.

Turns out that it could.  So it stayed on the swing chair for months. 

I never got around to doing anything more than that, until recently.

We had a big tidy up of the back yard and due to the age and effects of the sun, the swing chair was dismantled and taken to the tip.  This of course meant that the weather station had to move.

While we were at the tip, we stopped at the recycling depot to search of a few things to do with building a chicken run (still not done.. sigh) and I caught a few "J" masts poking out of a big bin.  Awesome.. just what I needed to put the weather station on.

So I grabbed it.  $10. 

With my brand new drill in hand I screwed the new J mast to the side of the shed.

I figured that the wind speed and direction sensors would be high enough up to avoid too much turbulance and the idea was to keep the tempreture sensor low hopefully keeping it shade for as much of the day as possible.

And here it is!

 

 

You can see one of the poles for the chook yard in the shot too.

 

Another shot, showing the tempreture sensor in the shade.

 

 

And another photo.

I think the tempreture sensor is going to be effected by the reflected heat from the roof of the shed.  I'll have to get myself another thermometer to test the temp in the shade to see how much it's being effected.

Anyway, that's the story of the weather station so far.  The fact that it's attached to something that I screwed to an inanimate object myself really is pretty awesome in my world.  For some stupid reason I always figure it's too hard and I'd never get it right and so never start on anything.

I'm quite chuffed so far.