Setting up a Weather WebCam on Linux

Weather webcams are always popular and it is easy and free to set one up yourself.  This article will show how to setup a simple USB webcam to produce still images and serve them on a local apache webserver.

Continue reading “Setting up a Weather WebCam on Linux”

Formatting xml in emacs

I had this problem of debugging some xml but when reading the output of some log4j it was almost impossible to read so I needed some way of prettifying the xml quickly.

For this example I have the following xml:

<?xml version="1.0"?><xml><iq xmlns="jabber:component:accept" from="test1@temp.retep.org/client" id="iq_257" to="service.retep.org" type="get"><query xmlns="some:namespace"/></iq></xml>

So how do we pretify this in emacs?

Well the first thing to do is to write an extension function & place it into your ~/.emacs file. Placing it here means that when you open emacs the extension is available:

(defun xml-format ()
  (interactive)
  (save-excursion
    (shell-command-on-region (mark) (point) "xmllint --format -" (buffer-name) t)
  )
)

Now this works by passing the buffer to the xmllint utility and replaces it with the output – in this case nicely formatted xml.

Now we need to install xmllint:

pi@lindesfarne: ~$ sudo apt-get install libxml2-utils

Ok so now open emacs and open the xml. To format first select the xml you want to format then Press Escape then x followed by xml-format & press return. You should then get the xml nicely formatted:

<?xml version="1.0"?>
<xml>
  <iq xmlns="jabber:component:accept" from="test1@temp.retep.org/client" id="iq_257" to="service.retep.org" type="get">
    <query xmlns="some:namespace"/>
  </iq>
</xml>

Installing a USB Weather Station on a Raspberry PI part 2

In the first article I covered how to install a weather station on a Raspberry PI. In the second part I’ll cover how to get it to upload data on an hourly basis to a website using FTP.

Getting the station to run hourly

First we need to get the station to run hourly. To do this I created a script called weatherupload which I placed under /usr/local/bin

pi@kell: ~$ sudo vi /usr/local/bin/weatherupload

Enter the following:

#!/bin/bash
cd /usr/local/weather
python Hourly.py -vvv data

Once saved make it executable and then edit the main crontab:

pi@kell: ~$ sudo chmod +x /usr/local/bin/weatherupload
pi@kell: ~$ sudo vi /etc/crontab

At the end of the file you need to add the following:

0 * * * * root /usr/local/bin/weatherupload

Save it and now every hour it will now run.

Note: I’ve placed it there and not under /etc/cron.hourly because

  1. cron.hourly runs once an hour, but not necessarily at the top of the hour. I a later article when I add twitter you want the tweet to be close to 0m rather than at a random time.
  2. I’ve found in the past that using crontab -e doesn’t always work, even for root but in the core crontab it just works

Uploading to a website

First to generate the graphs pywws uses gnuplot so we need to install it:

pi@kell: ~/sudo apt-get install gnuplot

Next we need to add some details to the stations weather.ini file. At the top theres a section called paths. Make sure those point to the relevant templates and graph_templates directories in your pywws install.
Next under the hourly section you should see a pair of lines:

plot = []
text = []

You need to add the plots and pages that need to be generated:

plot = ['7days.png.xml', '24hrs.png.xml', 'rose_24hrs.png.xml', 'rose_7days_nights.png.xml']
text = ['current.html', '24hrs.html', '6hrs.html', '7days.html', 'feed_hourly.xml', 'allmonths.html']

Finally theres the ftp section which needs configuring with the remote ftp server (your web host will give you these):

[ftp]
secure = False
site = ftp.example.com
local site = False
user = myaccount@example.com
directory = /weather/
password = mypassword

That’s about it. Now when you run the hourly script it will generate some simple pages & images to your website.

You can see an example of this over at maidstoneweather.com – although the uploaded templates only form part of that site.

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