mirror of
https://github.com/weewx/weewx.git
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1568 lines
75 KiB
HTML
1568 lines
75 KiB
HTML
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<title>The Weewx weather system</title>
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</head>
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<body>
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<h1 class="title">The <span class="code">weewx</span> weather system<br />
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Version 1.3</h1>
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<h1>Table of Contents</h1>
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<ol>
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<li>
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<p class="indent"><a href="#Copyright">Copyright</a></p>
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</li>
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<li>
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<p class="indent"><a href="#About_weewx">About <span class="code">weewx</span></a></p>
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</li>
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<li>
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<p class="indent"><a href="#Downloading_weewx">Downloading
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<span class="code">weewx</span></a></p>
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</li>
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<li>
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<p class="indent"><a href="#Prerequisites">Prerequisites</a></p>
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</li>
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<li>
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<p class="indent"><a href="#Installing_weewx">Installing <span class="code">
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weewx</span></a></p>
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</li>
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<li>
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<p class="indent"><a href="#Configuring_weewx">Configuring
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<span class="code">weewx</span></a></p>
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</li>
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<li>
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<p class="indent"><a href="#Running_weewx">Running <span class="code">weewx</span></a></p>
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</li>
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<li>
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<p class="indent"><a href="#Compatibility_with_wview">Compatibility with
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<span class="code">wview</span></a></p>
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</li>
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<li>
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<p class="indent"><a href="#HTML_Generation">HTML Generation</a></p>
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</li>
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<li>
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<p class="indent"><a href="#Monitoring_weewx">Monitoring <span class="code">
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weewx</span></a></p>
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</li>
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<li>
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<p class="indent"><a href="#Architectural_notes">Architectural Notes</a></p>
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</li>
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<li>
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<p class="indent"><a href="#Table_of_Tested_Versions">Table of Tested Versions</a></p>
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</li>
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</ol>
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<h1>1. <a name="Copyright">Copyright</a></h1>
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<p>(c) 2009 by Tom Keffer <<a href="mailto:tkeffer@gmail.com">tkeffer@gmail.com</a>></p>
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<p>This program is free software: you can redistribute it and/or modify it under
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the terms of the GNU General Public License as published by the Free Software Foundation,
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either version 3 of the License, or (at your option) any later version. </p>
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<p>This program is distributed in the hope that it will be useful, but WITHOUT ANY
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WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A
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PARTICULAR PURPOSE. See the GNU General Public License for more details. </p>
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<p>You should have received a copy of the GNU General Public License along with
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this program. If not, see <http://www.gnu.org/licenses/>
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<a href="http://www.gnu.org/licenses/">http://www.gnu.org/licenses</a>.</p>
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<h1>2. <a name="About_weewx">About <span class="code">weewx</span></a></h1>
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<p>I wrote <span class="code">weewx</span> over the winter of 2008-2009 for two
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reasons: it was a wet and miserable winter here in Oregon with not much else to
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do, so there was no good reason not to, and because I wanted a simple, easy-to-understand
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server to run my Davis VantagePro2 weather station on a Linux box. I had been using
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<a href="http://www.wviewweather.com/">wview</a>, which is a very high-performance,
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stable, and feature rich system authored by Michael Teel with lots of users. Written
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in C, it's an amazingly efficient system that can run on very underpowered boxes.
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In exchange, it's huge (55,000+ lines of code), tightly integrated in with its companion
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library, radlib (another 24,000+ lines), and complex. But, if you're looking to
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be in good company and you want to run on inexpensive, featherweight machines such
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as the <a href="http://en.wikipedia.org/wiki/NSLU2">Linksys NSLU2</a>, you can't
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beat it.</p>
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<p>Having made a career in C++ and Java, I was also interested in some more modern
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languages, so I thought I'd try either Python or Ruby (although, truth be told,
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the roots of Python are nearly as old as C++!). I picked Python because its libraries
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are more mature and there are many more choices for third party libraries.</p>
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<p><span class="code">Weewx</span> weighs in at about 7,000 lines of code, including
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its many comment lines although, to be fair, it is missing many features such as
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support for other weather stations, support for metric units, support for alarms,
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etc. On the other hand, it offers very powerful configuration and templating options,
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making it easy to customize. It is also architecturally very simple and easy to
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understand.</p>
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<h1>3. <a name="Downloading_weewx">Downloading <span class="code">weewx</span></a></h1>
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<p><span class="code">weewx</span> can be downloaded from its
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<a href="https://sourceforge.net">SourceForge</a> page:
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<a href="https://sourceforge.net/projects/weewx">https://sourceforge.net/projects/weewx</a>.
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</p>
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<h1>4. <a name="Prerequisites">Prerequisites</a></h1>
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<h2>4.1 Python</h2>
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<p>Python V2.5 or V2.6 is required. The newer V3.0 distribution will not work.</p>
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<h2>4.2 Required packages</h2>
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<p>The following external packages are required to use <span class="code">weewx</span>.</p>
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<ol>
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<li><a href="http://www.sqlite.org/">sqlite3</a> (Version 3.5 or greater) A
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SQL database written in C, which <span class="code">weewx</span> uses to store
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data pulled from the weather station. Comes with Debian and many other Linux
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distributions.</li>
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<li><a href="http://pypi.python.org/pypi/pysqlite/">pysqlite</a> (Version 2.5
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or greater) The Python interface to sqlite3.</li>
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<li><a href="http://pypi.python.org/pypi/configobj/">configobj</a> (Version
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4.5 or greater) Manages the configuration file <span class="code">weewx.conf</span>.</li>
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<li><a href="http://pypi.python.org/pypi/pyserial/2.4">pyserial</a> (Version
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1.35 or greater) Manages the serial connection to the weather station.</li>
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<li><a href="http://www.cheetahtemplate.org">Cheetah</a> (Version 2.0 or greater)
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The HTML templating engine.</li>
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<li><a href="http://pypi.python.org/pypi/PIL">Python Imaging Library</a> (Version
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1.1.6 or greater) Also known as PIL, this is included in many Python distributions.</li>
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</ol>
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<p>There are two general strategies for installing these prerequisites:</p>
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<ol>
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<li>Use operating system tools, such as <span class="code">apt-get</span> (or
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its graphical equivalent Synaptic Package Manager) for Debian/Ubuntu or
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<span class="code">yast</span> for SuSE; or</li>
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<li>Use the Python tool <span class="code">
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<a href="http://pypi.python.org/pypi/setuptools">easy_install</a></span>.</li>
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</ol>
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<p>Option #1 is easier, but if your Linux distribution does not come with such tools,
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you may have to use <span class="code">easy_install</span>. Brief instructions for
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both approaches are given below.</p>
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<h3>Installation on Debian distributions (including Ubuntu) using
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<span class="code">apt-get</span></h3>
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<p>The instructions that follow are for using the Debian tool <span class="code">
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apt_get</span>, but the same package names would be used should you chose to use
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a graphical interface such as the Synaptic Package Manager.</p>
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<h4>sqlite3</h4>
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<p>My Ubuntu 8.10 system came with V3.5.9, which works just fine. However, if you
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need to install:</p>
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<p class="tty">sudo apt-get install sqlite3</p>
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<h4>pysqlite</h4>
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<p>Easily installed:</p>
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<p class="tty">sudo apt-get install python-pysqlite2</p>
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<h4>configobj</h4>
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<p>Easily installed:</p>
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<p class="tty">sudo apt-get install python-configobj</p>
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<h4>pyserial</h4>
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<p>Easily installed:</p>
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<p class="tty">sudo apt-get install python-serial</p>
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<h4>Cheetah</h4>
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<p>Easily installed:</p>
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<p class="tty">sudo apt-get install python-cheetah</p>
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<h4>Python Imaging Library (PIL)</h4>
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<p>My version of Python came with V1.1.6, which works great. Nothing needs to be
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done.</p>
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<h3>Installation on SuSE using <span class="code">yast</span></h3>
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<p>My SuSE 11.1 system came with some of the prerequisites installed, some available
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through <span class="code">yast</span>, and three that required
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<span class="code">easy_install</span>. To start, you will have to install the gcc
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compiler:</p>
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<p class="tty">sudo yast -i gcc</p>
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<p>Then install <span class="code">easy_install</span>:</p>
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<p class="tty">sudo yast -i python-setuptools</p>
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<p>On my system, some scripts wanted to install themselves into
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<span class="code">/usr/local/lib/python2.6/site-packages</span>, which didn't exist.
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If this is the case, you may have to create these directories before running
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<span class="code">easy_install</span>:</p>
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<p class="tty">sudo mkdir /usr/local/lib/python2.6</p>
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<p class="tty">sudo mkdir /usr/local/lib/python2.6/site-packages</p>
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<h4>sqlite3</h4>
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<p>My SuSE 11.1 system came with V3.6.4, which works just fine. However, if you
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need to install:</p>
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<p class="tty">sudo yast -i sqlite3</p>
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<h4>pysqlite</h4>
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<p>Install using <span class="code">easy_install</span>. See
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<a href="#pysqlite_using_easy_install">comments below</a> about installing pysqlite
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using <span class="code">easy_install</span>. On my SuSE 11.1 system, I had to install
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the gcc compiler and the sqlite3 development environment first:</p>
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<p class="tty">sudo yast -i gcc</p>
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<p class="tty">sudo yast -i sqlite-devel</p>
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<p>Then I was able to install pysqlite using <span class="code">easy_install</span>.
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However, because the hosting site for pysqlite had changed recently, I had to give
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the URL explicitly:</p>
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<p class="tty">sudo easy_install
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<a href="http://pysqlite.googlecode.com/files/pysqlite-2.5.5.tar.gz">http://pysqlite.googlecode.com/files/pysqlite-2.5.5.tar.gz</a></p>
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<h4>configobj</h4>
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<p>Install using <span class="code">easy_install</span>:</p>
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<p class="tty">sudo easy_install configobj</p>
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<h4>pyserial</h4>
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<p>Install using <span class="code">yast</span>:</p>
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<p class="tty">sudo yast-i python-serial</p>
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<h4>Cheetah</h4>
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<p>Install using <span class="code">easy_install</span> (My system emitted a bunch
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of, apparently, benign warnings):</p>
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<p class="tty">sudo easy_install Cheetah</p>
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<h4>Python Imaging Library (PIL)</h4>
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<p>Install using <span class="code">yast</span></p>
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<p class="tty">sudo yast -i python-imaging</p>
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<h3>Installation using <span class="code">easy_install</span></h3>
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<p>An alternative approach to installing the required packages is by using the Python
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setup tool "<span class="code">easy_install</span>", part of the
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<a href="http://pypi.python.org/pypi/setuptools">python-setuptools package</a>.
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Refer to their instructions on how to install this tool.</p>
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<p>Once installed, installing the rest of the packages is very easy.</p>
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|
<h4>sqlite3</h4>
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<p>My Ubuntu 8.10 system came with V3.5.9, which works just fine. If you do not
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have sqlite3, refer to <a href="http://www.sqlite.org">the sqlite webpage</a> for
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|
installation instructions.</p>
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<h4><a name="pysqlite_using_easy_install">pysqlite</a></h4>
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|
<p>While Version 2.3.X of <a href="http://pypi.python.org/pypi/pysqlite/">pysqlite</a>
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is included with many versions of Python, the more recent 2.5.X or greater is required
|
|
in order to take advantage of transaction contexts. Hence, you may have to install
|
|
or upgrade. Because pysqlite builds a C library, you may have to install the Python
|
|
development environment first, if you have not already done so. Generally, this
|
|
means installing the gcc compiler. You may also have to install the sqlite3 development
|
|
environment as well.</p>
|
|
<p>With the development environment in place, you can easily build and install pysqlite:</p>
|
|
<p class="tty">easy_install pysqlite</p>
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<p>If your system already has a version of pysqlite installed, but it is not a high
|
|
enough version (<span class="code">easy_install</span> will tell you the version
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|
you have), then you may have to force an upgrade:</p>
|
|
<p class="tty">easy_install --upgrade pysqlite</p>
|
|
<p>Note that at the time of this writing (24 Oct 2009), the hosting site for pysqlite
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has changed to one on <a href="http://pysqlite.googlecode.com">googlecode</a>, and
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<span class="code">easy_install</span> could not find it. You may have to find and
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|
give the URL explicitly to <span class="code">easy_install</span> (adjust version
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|
numbers as necessary):</p>
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<p class="tty">easy_install http://pysqlite.googlecode.com/files/pysqlite-2.5.5.tar.gz</p>
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<h4>configobj</h4>
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<p>Easily installed:</p>
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<p class="tty">easy_install configobj</p>
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<h4>pyserial</h4>
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<p class="indent"><span class="code">easy_install pyserial</span></p>
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<h4>Cheetah</h4>
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<p class="indent"><span class="code">easy_install Cheetah</span></p>
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<h4>Python Imaging Library (PIL)</h4>
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|
<p>My version of Python came with V1.1.6, which works great.</p>
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<h2>4.3 System requirements</h2>
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<p>I run <span class="code">weewx</span> on a 500MHz system with an AMD Geode processor
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and 512 MB of memory. Configured this way, it consumes about 5% of the CPU
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and about 75MB of total memory.</p>
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<h2>4.4 Weather station hardware requirements</h2>
|
|
<p>At this point, only the
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<a href="http://www.davisnet.com/weather/products/vantagepro.asp">Davis VantagePro2</a>
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is supported, and even then, only the "Revision B" version (firmware dated on or
|
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after 22 April 2002). It would be very easy to port to a "Revision A" station or
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even the original VantagePro, but I don't have access to the hardware to test it.</p>
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<h1>5. <a name="Installing_weewx">Installing <span class="code">weewx</span></a></h1>
|
|
<p>Because <span class="code">weewx</span> is "Pure Python", that is it is 100%
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Python with no "C" modules to compile, installing it is very easy. Furthermore,
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it uses the standard Python <a href="http://docs.python.org/install/index.html">
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distutils</a> install method, which is very easy and flexible. Detailed instructions
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follow.</p>
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<h2>5.1 Unpacking</h2>
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<p>Start by unpack the tar ball (substitute your version for X.Y.Z) into any convenient
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directory where you have write permission</p>
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<p class="tty">tar xvf weewx-X.Y.Z</p>
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<p>Then change directory into it:</p>
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<p class="tty">cd weewx-X.Y.Z</p>
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<h2>5.1 Choosing the <span class="code">WEEWX_ROOT</span> directory</h2>
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<p>Next step is figuring out where you want to install <span class="code">weewx</span>.
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If <span class="code"><em>WEEWX_ROOT</em></span> symbolizes the root location of
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the <span class="code">weewx</span> directory hierarchy, then</p>
|
|
<ul>
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<li><span class="code"><em>$WEEWX_ROOT</em>/bin</span> is where the Python packages
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and scripts are installed;</li>
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<li><span class="code"><em>$WEEWX_ROOT</em>/weewx.conf</span> is the configuration
|
|
file;</li>
|
|
<li><span class="code"><em>$WEEWX_ROOT</em>/templates</span> is where the html
|
|
templates live;</li>
|
|
<li><span class="code"><em>$WEEWX_ROOT</em>/archive</span> is the directory
|
|
where the sqlite3 database lives;</li>
|
|
<li><em>$</em><span class="code"><em>WEEWX_ROOT</em>/public_html</span> is where
|
|
generated html and .png images are put.</li>
|
|
</ul>
|
|
<p>By default, the location for <span class="code"><em>WEEWX_ROOT</em></span> is
|
|
<span class="code">/home/weewx</span>. However, it can be changed by editing the
|
|
file <span class="code">setup.cfg</span>. If you wish to install someplace else,
|
|
open up <span class="code">setup.cfg</span> and change the line</p>
|
|
<p class="tty">home = /home/weewx</p>
|
|
<p>to reflect your decision.</p>
|
|
<h2>5.2 Build and install</h2>
|
|
<p>Build the distribution</p>
|
|
<p class="tty">./setup.py build</p>
|
|
<p>(Because <span class="code">weewx</span> is pure Python this doesn't actually
|
|
build anything, but it does arrange files for the final installation)</p>
|
|
<p>Then install it. If you have write permission in the directory where
|
|
<span class="code">weewx</span> will go (<em>i.e.</em>, <span class="code"><em>$WEEWX_ROOT</em></span>),
|
|
then type</p>
|
|
<p class="tty">./setup.py install</p>
|
|
<p>Otherwise, if you do not have write permission, you will have to use sudo:</p>
|
|
<p class="tty">sudo ./setup.py install</p>
|
|
<h3>Upgrading</h3>
|
|
<p>If you are upgrading from a previous version of <span class="code">weewx</span>,
|
|
you should follow the directions above. In particular, be sure to set
|
|
<span class="code">home</span> in the file <span class="code">setup.cfg</span>. </p>
|
|
<p>The build and install process will do the following for you.</p>
|
|
<ul>
|
|
<li>Save your old template directories as <span class="code"><em>$WEEWX_ROOT</em>/templates.YYYYMMDDHHMMSS</span>
|
|
where YYYYMMDDHHMMSS is a timestamp;</li>
|
|
<li>Merge any changes you've made to your old configuration file
|
|
<span class="code">weewx.conf</span> into the new configuration file, then install
|
|
the merged copy (this effectively causes changes you've made to override the
|
|
values in the shipped version of <span class="code">weewx.conf</span>);</li>
|
|
<li>Save a copy of your old <span class="code">weewx.conf</span> as
|
|
<span class="code"><em>$WEEWX_ROOT</em>/weewx.conf.YYYYMMDDHHMMSS</span>.</li>
|
|
</ul>
|
|
<h2>5.3 Permissions</h2>
|
|
<p>Strictly speaking it is not necessary to install or run <span class="code">weewx</span>
|
|
with root privileges. You only need read/write access to the serial port for your
|
|
hardware. For example, if your hardware has a USB interface, on Ubuntu and SuSE:</p>
|
|
<p class="tty">sudo chmod a+rw /dev/ttyUSB0</p>
|
|
<p>Once done, if you edit <span class="code">setup.cfg</span> to install into a
|
|
directory where you have write permissions, you can install and run
|
|
<span class="code">weewx</span> without any root privileges at all. </p>
|
|
<h2>5.4 Final note on installation</h2>
|
|
<p>Because <span class="code">weewx</span> is pure Python, it actually does not
|
|
have to be "built" and "installed" at all! You can just simply run it out of whatever
|
|
directory you unpack it into (after, of course, editing <span class="code">weewx.conf</span>
|
|
to reflect your local environment). I do this all the time when testing. However,
|
|
the <span class="code">setup.py</span> script does include special provisions for
|
|
updating your configuration file <span class="code">weewx.conf</span>, which can
|
|
be handy when upgrading to a later version.</p>
|
|
<h1>6. <a name="Configuring_weewx">Configuring <span class="code">weewx</span></a></h1>
|
|
<p>This section covers configuring your archive and statistical database (if necessary;
|
|
this step is required only if you are moving from
|
|
<a href="http://www.wviewweather.com/">wview</a> to weewx), configuring your weather
|
|
station, and configuring the configuration file <span class="code">weewx.conf</span>.</p>
|
|
<p>In the following, <span class="code"><em>$WEEWX_ROOT</em></span> refers to the
|
|
<span class="code">weewx</span> root directory, generally <span class="code">/home/weewx</span>.
|
|
</p>
|
|
<h2>6.1 Configuring the databases</h2>
|
|
<p>This section is necessary only if you are moving from
|
|
<a href="http://www.wviewweather.com/">wview</a> to <span class="code">weewx</span>
|
|
and wish to transfer your old data over. If you are starting afresh, you do not
|
|
need to follow this section — the two main databases are created and populated automatically
|
|
by <span class="code">weewx</span>.</p>
|
|
<p>Two databases are maintained by weewx:</p>
|
|
<ul>
|
|
<li><span class="code"><em>$WEEWX_ROOT/$archive_file</em></span> (nominally
|
|
<span class="code">/home/weewx/archive/weewx.sdb</span>)</li>
|
|
<li><span class="code"><em>$WEEWX_ROOT/$stats_file</em></span> (nominally
|
|
<span class="code">/home/weewx/archive/stats.sdb</span>)</li>
|
|
</ul>
|
|
<p>Because wview and weewx use identical schema for the first of these (the archive
|
|
database), it can be just copied over. However, the second (the statistical databases)
|
|
are different — the weewx statistical database must be built manually and backfilled.
|
|
This is done using the configuration script <span class="code">configure.py</span>.
|
|
</p>
|
|
<p>Here's a summary of how to transfer your wview data to <span class="code">weewx</span>.</p>
|
|
<p class="tty">mkdir <em>$WEEWX_ROOT</em>/archive</p>
|
|
<p class="tty">cp /usr/local/var/wview/archive/wview-archive.sdb <span class="code"><em>$WEEWX_ROOT</em></span>/archive/weewx.sdb</p>
|
|
<p class="tty"><em>$WEEWX_ROOT</em>/bin/configure.py --create-stats <em>$WEEWX_ROOT</em>/weewx.conf</p>
|
|
<p class="tty"><em>$WEEWX_ROOT</em>/bin/configure.py --backfill-stats <em>$WEEWX_ROOT</em>/weewx.conf</p>
|
|
<p>If your existing database is large, backfilling could take some time. On my modest
|
|
500 MHz <a href="http://www.fit-pc.com/new/fit-pc-slim-specifications.html">fit-PC</a>
|
|
with 512 MB of memory it took a little over 4 minutes for a year and a half (25
|
|
MB) of data (while wview was running in the background).</p>
|
|
<h2>6.2 Configuring your weather station</h2>
|
|
<p>The only two variables <span class="code">weewx</span> tries to manage on the
|
|
VantagePro are the time and the archive interval. </p>
|
|
<h3>Time</h3>
|
|
<p>The time on the VP is automatically synchronized with the <span class="code">
|
|
weewx</span> server every four hours. However, you should run a NTP daemon on your
|
|
server to insure that it is synchronized with the correct time. Doing so will greatly
|
|
reduce errors, especially if you send data to services such as the Weather Underground.</p>
|
|
<h3><a name="Archive_interval">Archive interval</a></h3>
|
|
<p>The archive interval is set in the main configuration file <span class="code">
|
|
<em>$WEEWX_ROOT</em>/weewx.conf. </span>Look for the entry <span class="code">archive_interval</span>
|
|
in the <span class="code">VantagePro</span> section. Set it to the number of seconds.
|
|
Valid entries are 60, 300, 600, 900, 1800, 3600, and 7200. However, if you are ftp'ing
|
|
lots of files to a server, setting it to 60 seconds may not give enough time to
|
|
have them all uploaded before the next archive record is due. If this is the case,
|
|
you should pick an archive interval of at least 300 seconds, or trim the number
|
|
of files you are using.</p>
|
|
<p>After setting to the desired interval, run the <span class="code">configure.py</span>
|
|
script to set it on the VantagePro. If it differs from the old archive interval,
|
|
the main memory log of the VantagePro will be cleared. </p>
|
|
<p class="tty"><em>$WEEWX_ROOT</em>/bin/configure.py --configure-VantagePro $WEEWX_ROOT/weewx.conf</p>
|
|
<h2>6.3 Editing the configuration file <span class="code">weewx.conf</span></h2>
|
|
<p>Virtually every conceivable configuration option is in the configuration file
|
|
<span class="code"><em>$WEEWX_ROOT</em>/weewx.conf</span>. Most of the important
|
|
ones are up near the top of the file. They are all documented in this section, although
|
|
you can safely ignore most of them. The truly important ones, the ones you are likely
|
|
to have to customize for your station, are shown in <span class="bold_n_blue">
|
|
<strong>bold face and in blue</strong></span>. </p>
|
|
<p>Default values are provided for many of them, meaning that if they are not listed
|
|
in the configuration file <em>at all</em>, <span class="code">weewx</span> will
|
|
pick sensible values. When the documentation below gives a "default value" this
|
|
is what it means. However, all options have been given values in the configuration
|
|
file that ships with <span class="code">weewx</span>, so you can see what they look
|
|
like. The value given in this shipped configuration file is not necessarily the
|
|
same as the "default value".</p>
|
|
<p>What follows is organized by the different sections of the configuration file.</p>
|
|
<h3>General</h3>
|
|
<p>The options declared at the top are not actually part of any section. There are
|
|
two:</p>
|
|
<h4 class="config_option">debug</h4>
|
|
<p>Set to 1 to have the program perform extra debug checks, as well as emit extra
|
|
information on the log file. Otherwise, set to 0. Default is 0 (no debug).</p>
|
|
<h4 class="config_option">socket_timeout</h4>
|
|
<p>Set to how long to wait before declaring a socket time out. This is used when
|
|
FTP'ing data to a web server or sending data to the Weather Underground. Twenty
|
|
(20) seconds is reasonable. Default is 20.</p>
|
|
<h3 class="config_section">[Station]</h3>
|
|
<p>This section covers options relating to the entire weather station setup. </p>
|
|
<h4 class="config_option">WEEWX_ROOT</h4>
|
|
<p>Set to the root directory of the <span class="code">weewx</span> file hierarchy
|
|
for this station, nominally '<span class="code">/home/weewx</span>'. This value
|
|
will be set automatically by the setup script <span class="code">setup.py</span>
|
|
to reflect the choice you made in the configuration file <span class="code">setup.cfg</span>.
|
|
Required. No default.</p>
|
|
<h4 class="config_important">location</h4>
|
|
<p>The station location should be a string that describes the geography of where
|
|
you weather station is located, such as 'Hood River, Oregon'. Required. No default.</p>
|
|
<h4 class="config_important">latitude<br />
|
|
longitude</h4>
|
|
<p>The lat/lon should be set in decimal degrees, negative for southern and eastern
|
|
hemispheres, respectively. Required. No default.</p>
|
|
<h4 class="config_important">altitude</h4>
|
|
<p>Should be set to the altitude of the station. In this version, the only unit
|
|
accepted is feet. Required. No default.</p>
|
|
<h4 class="config_important">rain_year_start</h4>
|
|
<p>If your area uses a rain year that starts on something other than the first of
|
|
January, you may want to set this variable. For example, set to 10 if your rain
|
|
year starts in October (as mine does). Default is 1.</p>
|
|
<h4 class="config_important">radar_url</h4>
|
|
<p>This variable is available in the HTML templates. Set it to an appropriate URL
|
|
to display a radar image for your area. No default.</p>
|
|
<h4 class="config_option">heating_base<br />
|
|
cooling_base</h4>
|
|
<p>Set to the base temperature for calculating heating and cooling degree-days,
|
|
respectively. The default is 65.0 for both.</p>
|
|
<h4 class="config_option">hemispheres</h4>
|
|
<p>Set to suitable abbreviations for the four hemispheres. Default is "N", "S",
|
|
"E", "W"</p>
|
|
<h4 class="config_option">clock_check</h4>
|
|
<p>How often to check the station's onboard clock for drift, in seconds. Default
|
|
is 14400 (every 4 hours)</p>
|
|
<h4 class="config_option">cache_loop_data</h4>
|
|
<p>Set to 1 (one) to cache LOOP data, otherwise, set to zero. Most users will
|
|
not want to change this unless you have a specialized application. Default is 1
|
|
(cache LOOP data).</p>
|
|
<h4 class="config_option">station_type</h4>
|
|
<p>Set to the type of hardware you are using. For this version, only '<span class="code">VantagePro</span>'
|
|
is accepted. Required.</p>
|
|
<h3 class="config_section">[VantagePro]</h3>
|
|
<p>This section is for options relating to the VantagePro hardware.</p>
|
|
<h4 class="config_important">port</h4>
|
|
<p>Set to the port name used by your station. Example, /<span class="code">dev/ttyUSB0</span>
|
|
is a common location for USB ports under Debian, <span class="code">/dev/ttyS0</span>
|
|
for serial ports. Required. No default.</p>
|
|
<h4 class="config_option">baudrate</h4>
|
|
<p>Set to the baudrate of your station. The default is 19200.</p>
|
|
<h4 class="config_important">archive_interval</h4>
|
|
<p>Set to the desired archive interval of your station, in seconds. This variable
|
|
is only used when setting up your station. Otherwise, this value is read directly
|
|
from the station. Required if you <a href="#Archive_interval">configure your station</a>.
|
|
No default.</p>
|
|
<h4 class="config_option">iss_id</h4>
|
|
<p>Set to the ID number of your Integrated Sensor Suite (ISS). This is used in the
|
|
formula to calculate reception quality for wireless stations. The default is 1.</p>
|
|
<h4 class="config_option">archive_delay</h4>
|
|
<p>How long to wait in seconds after the top of an archiving interval before fetching
|
|
new data off the station. For example, if your archive interval is 5 minutes and
|
|
archive_delay is set to 15, then the data will be fetched at 00:00:15, 00:05:15,
|
|
00:10:15, etc. This delay is to give the station a few seconds to archive the data
|
|
internally, and in case your server has any other tasks to do at the top of the
|
|
minute. Default is 15 seconds.</p>
|
|
<h4 class="config_option">timeout</h4>
|
|
<p>How many seconds to wait for a response from the station before giving
|
|
up. Default is 5 seconds.</p>
|
|
<h4 class="config_option">wait_before_retry</h4>
|
|
<p>How many seconds to wait before retrying again. Unless you have a good reason
|
|
to, this value should not be changed from the default, as it is long enough for
|
|
the station to offer new data, but not so long as to go into a new loop packet (which
|
|
arrive every 2 seconds). Default is 1.2 seconds.</p>
|
|
<h4 class="config_option">max_retries</h4>
|
|
<p>How many times to try again before giving up. Default is 4.</p>
|
|
<h4 class="config_option">max_drift</h4>
|
|
<p>The maximum amount of drift to tolerate, in seconds, in the VantagePro's onboard
|
|
clock, before resetting the clock. Default is 5.</p>
|
|
<h4 class="config_option">unit_system</h4>
|
|
<p>What unit system is in use on your weather station hardware. Possible values
|
|
are '1' (Imperial) or '2' (Metric). As far as I know, all Davis instruments support
|
|
only Imperial. In any case, Imperial is the only system supported by
|
|
<span class="code">weewx</span>. Default is 1.</p>
|
|
<h3 class="config_section">[FTP]</h3>
|
|
<p>If you FTP your images and HTML files to an external web server,
|
|
<span class="code">weewx</span> can FTP them for you. It does an incremental update,
|
|
that is, it only FTPs any files that have changed, saving outgoing bandwidth with
|
|
your Internet connection.</p>
|
|
<p>If you do not use such a server, comment out the first four options below.</p>
|
|
<p class="config_important">user</p>
|
|
<p>Set to the username you use for your FTP connection to your web server. Required.
|
|
No default.</p>
|
|
<p class="config_important">password</p>
|
|
<p>Set to the password you use for your FTP connection to your web server. Required.
|
|
No default.</p>
|
|
<p class="config_important">server</p>
|
|
<p>Set to the name of your web server (e.g., <a href="http://www.threefools.org">
|
|
www.threefools.org</a>, in my case). Required. No default</p>
|
|
<p class="config_important">path</p>
|
|
<p>Set to the path where the weather data will be stored on your webserver (e.g.,
|
|
'<span class="code">/weather</span>'). NB: some FTP servers require a
|
|
leading slash ('<span class="code">/</span>'), some don't. Required. No default.</p>
|
|
<h4 class="config_important">passive</h4>
|
|
<p>Set to 1 if you wish to use the more modern, FTP passive mode, 0 if you wish
|
|
to use active mode. Passive mode generally works better through firewalls, but not
|
|
all FTP servers do a good job of supporting it. See
|
|
<a href="http://slacksite.com/other/ftp.html">Active FTP vs. Passive FTP, a Definitive
|
|
Explanation</a> for a good explanation of the difference. Default is 1 (passive
|
|
mode).</p>
|
|
<h4 class="config_option">max_retries</h4>
|
|
<p><span class="code">Weewx</span> will try up to this many times to FTP a file
|
|
up to your server before giving up. Default is 3.</p>
|
|
<h3 class="config_section">[Wunderground]</h3>
|
|
<p><span class="code">Weewx </span>can send your current data to the Weather
|
|
Underground. If you do not wish to do this, comment out the two options below.</p>
|
|
<h4 class="config_option"><span class="config_important">station</span></h4>
|
|
<p>Set to your Weather Underground station ID (e.g., <span class="code">KORHOODR3</span>).
|
|
Required.</p>
|
|
<h4 class="config_important">password</h4>
|
|
<p>Set to your Weather Underground password. Required.</p>
|
|
<h3 class="config_section">[Archive]</h3>
|
|
<p>This section is for configuring the sqlite3 database on which the station archive
|
|
data is stored.</p>
|
|
<h4 class="config_option">archive_file</h4>
|
|
<p>The path, relative to the <span class="code">WEEWX_ROOT </span>directory, to
|
|
the database. Required</p>
|
|
<h4 class="config_option">unit_system</h4>
|
|
<p>What unit system to use inside the database. Required. The only one supported
|
|
right now is '1', the Imperial (U.S.) system</p>
|
|
<h3 class="config_section">[Stats]</h3>
|
|
<p>This section is for configuring the sqlite3 database on which the station statistics
|
|
are stored.</p>
|
|
<h4 class="config_option">stats_file</h4>
|
|
<p>The path, relative to the <span class="code">WEEWX_ROOT </span>directory to the
|
|
statistical database. Required.</p>
|
|
<h4 class="config_option"><a name="stats_types">stats_types</a></h4>
|
|
<p>The list of types for which statistics will be kept. Types not listed will not
|
|
be available for generating HTML pages. Optional. The default is all types, resulting
|
|
in a possibly much bigger than necessary stats database (do you really have four
|
|
different soil moisture sensors?) The list that ships with the configuration file
|
|
will work for most stations and probably will not have to be modified.</p>
|
|
<h3 class="config_section">[Images]</h3>
|
|
<p>This section, which controls which images (plots) get generated and with which
|
|
options, is by far the most complicated. However, it is extremely flexible and powerful.</p>
|
|
<h4>Time periods</h4>
|
|
<p>It consists of one or more sub-sections, one for each time period (day, week,
|
|
month, and year). These sub-sections define the nature of aggregation and plot types
|
|
for the time period. For example, here's a typical set of options for sub-section
|
|
<span class="code">[[month_images]]</span>, controlling how images that cover a
|
|
month period are generated:</p>
|
|
<p class="tty">[[month_images]]</p>
|
|
<p class="tty"> x_label_format = %d</p>
|
|
<p class="tty"> bottom_label_format = %m/%d/%y %H:%M</p>
|
|
<p class="tty"> time_length = 2592000 # == 30 days</p>
|
|
<p class="tty"> aggregate_type = avg</p>
|
|
<p class="tty"> aggregate_interval = 10800 # == 3 hours</p>
|
|
<p>The option <span class="code">x_label_format</span> gives a
|
|
<a href="http://docs.python.org/library/datetime.html#strftime-behavior">strftime()</a>
|
|
type format for the x-axis. In this example, it will only show days (format option
|
|
"<span class="code">%d</span>"). The <span class="code">bottom_label_format</span>
|
|
is the format used to time stamp the image at the bottom. In this example, it will
|
|
show the time as <span class="code">10/25/09 15:35</span>. A plot will cover a nominal
|
|
30 days, and all items included in it will use an aggregate type of averaging over
|
|
3 hours. </p>
|
|
<h4>Image files</h4>
|
|
<p>Within each sub-section is another nesting, one for each image to be generated.
|
|
The title of each sub-sub-section is the filename to be used for the image.
|
|
Finally, at one additional nesting level (!) are the logical names of all the
|
|
line types to be drawn in the image. Values specified in the
|
|
level above can be overridden. For example, here's a typical set of options for
|
|
sub-sub-section <span class="code">[[[monthrain]]]</span>: </p>
|
|
<p class="tty">[[[monthrain]]]</p>
|
|
<p class="tty"> plot_type = bar</p>
|
|
<p class="tty"> yscale = None, None, 0.02</p>
|
|
<p class="tty"> [[[[rain]]]]</p>
|
|
<p class="tty"> aggregate_type = sum</p>
|
|
<p class="tty"> aggregate_interval = 86400</p>
|
|
<p class="tty"> label = Rain (daily avg)</p>
|
|
<p>This will generate an image file with name <span class="code">monthrain.png</span>.
|
|
It will be a bar plot. Option <span class="code">yscale</span> controls the y-axis
|
|
scaling — if left out, the scale will automatically be chosen. However, in this
|
|
example we are choosing to exercise some degree of control by specifying values
|
|
explicitly. It is a 3-way tuple (<span class="code">ylow</span>,
|
|
<span class="code">yhigh</span>, <span class="code">min_interval</span>), where
|
|
<span class="code">ymin</span> and <span class="code">ymax</span> are the minimum
|
|
and maximum y-axis values, respectively, and <span class="code">min_interval</span>
|
|
is the minimum tick interval. If set to '<span class="code">None</span>', the corresponding
|
|
value will be automatically chosen. So, in this example, we are letting
|
|
<span class="code">weewx</span> pick sensible y minimum and maximum values, but
|
|
we are requiring that the tick increment (<span class="code">min_interval</span>)
|
|
be at least 0.02. </p>
|
|
<p>Continuing on with the example above, there will be only one line and it will
|
|
have logical name '<span class="code">rain</span>'. Because we haven't said
|
|
otherwise, the SQL data type to be used for this line will be the same as its
|
|
logical name, that is, <span class="code">rain</span>, but this can be
|
|
overridden (see below). The aggregation type will be summing (overriding
|
|
the averaging specified in sub-section <span class="code">[[month_images]]</span>,
|
|
so you get the total rain over the aggregate period rather than the average) over
|
|
an aggregation interval of 86,400 seconds (one day). The plot line will be titled
|
|
with the indicated label ('<span class="code">Rain (daily avg)</span>')</p>
|
|
<h4>Including more than one SQL type in a plot</h4>
|
|
<p>More than one SQL type can be included in a plot. For example, here's how to
|
|
generate a plot with the week's outside temperature as well as dewpoint:</p>
|
|
<p class="tty">[[[monthtempdew]]]</p>
|
|
<p class="tty"> [[[[outTemp]]]]</p>
|
|
<p class="tty"> [[[[dewpoint]]]]</p>
|
|
<p>This would create an image in file <span class="code">monthtempdew.png</span>
|
|
that includes a line plot of both outside temperature and dewpoint.</p>
|
|
<h4>Including the same SQL type more than once in a plot</h4>
|
|
<p>Another example. Say you want a plot of the day's temperature, overlaid with
|
|
hourly averages. Here, you are using the same data type ('<span class="code">outTemp</span>')
|
|
for both plot lines, the first with averages, the second without. If you do the
|
|
obvious it won't work:</p>
|
|
<p class="tty">## WRONG ##</p>
|
|
<p class="tty">[[[daytemp_with_avg]]]</p>
|
|
<p class="tty"> [[[[outTemp]]]]</p>
|
|
<p class="tty"> aggregate_type = avg</p>
|
|
<p class="tty"> aggregate_interval = 3600</p>
|
|
<p class="tty"> [[[[outTemp]]]] # OOPS! The same section name appears more than
|
|
once!</p>
|
|
<p>The option parser does not allow the same section name ('<span class="code">outTemp</span>'
|
|
in this case) to appear more than once at a given level in the configuration
|
|
file, so an error will be declared (technical reason: formally, the sections are
|
|
an unordered dictionary). If you wish for the same SQL type to appear more than
|
|
once in a plot then there is a trick you must know: use option
|
|
<span class="code">data_type</span>. This will override the default action that
|
|
the logical line name is used for the SQL type. So, our example would look like
|
|
this:</p>
|
|
<p class="tty">[[[daytemp_with_avg]]]</p>
|
|
<p class="tty"> [[[[a_logical_name]]]]</p>
|
|
<p class="tty"> data_type = outTemp</p>
|
|
<p class="tty"> aggregate_type = avg</p>
|
|
<p class="tty"> aggregate_interval = 3600</p>
|
|
<p class="tty"> [[[[outTemp]]]]</p>
|
|
<p>Here, the first logical line has been given the name "<span class="code">a_logical_name</span>"
|
|
to distinguish it from the second line "<span class="code">outTemp</span>". We
|
|
have specified that the first line will use data type <span class="code">outTemp</span>
|
|
and that it will use averaging over a one hour period. The second also uses
|
|
<span class="code">outTemp</span>, but will not use averaging.</p>
|
|
<h4>Progressive vector plots</h4>
|
|
<p><span class="code">Weewx</span> can produce progressive vector plots as well as the more conventional
|
|
x-y plots. To produce these, use plot type '<span class="code">vector</span>'.
|
|
You need a vector type to produce this kind of plot. There are two: '<span class="code">windvec</span>',
|
|
and '<span class="code">windgustvec</span>'. While they don't actually appear in
|
|
the SQL database, <span class="code">weewx</span> understands that they represent special vector-types.
|
|
The first, '<span class="code">windvec</span>', represents the average wind in
|
|
an archive period, the second, '<span class="code">windgustvec</span>' the max
|
|
wind in an archive period. Here's how to produce a progressive vector plot of
|
|
the year's biggest daily wind gusts, along with daily averages:</p>
|
|
<p class="tty">[[[yeargustoverlay]]]</p>
|
|
<p class="tty"> aggregate_interval = 86400</p>
|
|
<p class="tty"> [[[[windvec]]]]</p>
|
|
<p class="tty"> plot_type = vector</p>
|
|
<p class="tty"> aggregate_type = avg</p>
|
|
<p class="tty"> [[[[windgustvec]]]]</p>
|
|
<p class="tty"> plot_type = vector</p>
|
|
<p class="tty"> aggregate_type = max</p>
|
|
<p>This will produce an image file with name <span class="code">
|
|
yeargustoverlay.png</span>. It will consist of two progressive vector plots,
|
|
both using daily aggregation (86,400 seconds). For the first set of vectors, the daily
|
|
average will be used. In the second, the max of the gusts will be used.</p>
|
|
<p>By default, the sticks in the progressive wind plots point towards the wind
|
|
source. That is, the stick for a wind from the west will point left. If you have
|
|
a chronic wind direction (as I do), you may want to rotate the default direction
|
|
so that all the vectors don't line up over the x-axis, overlaying each other. Do
|
|
this by using option <span class="code">vector_rotate</span>. For example, with
|
|
my chronic westerlies, I set <span class="code">vector_rotate</span> to 90.0, so
|
|
winds out of the west point straight up. </p>
|
|
<p>If you use this kind of plot (the out-of-the-box version of
|
|
<span class="code">weewx</span> includes daily, weekly, monthly, and yearly
|
|
progressive wind plots), a small compass rose will be put in the lower-left
|
|
corner of the image to show the orientation of North.</p>
|
|
<h4>Summary</h4>
|
|
<p>Studying this section in the shipped version of <span class="code">weewx.conf</span>
|
|
will give you ideas about the many different image plot configurations that are
|
|
possible without hacking the code. </p>
|
|
<h3 class="config_section">[Labels]</h3>
|
|
<p>This section controls how images are labeled. It consists of three sub-sections:</p>
|
|
<h4 class="config_option">[[Generic]]</h4>
|
|
<p>This sub-sections specifies default labels to be used for each SQL type. For
|
|
example, options</p>
|
|
<p class="tty">inTemp = Inside Temperature</p>
|
|
<p class="tty">outTemp = Outside Temperature</p>
|
|
<p>would cause the given labels to be used for plots involving SQL types
|
|
<span class="code">inTemp </span>and <span class="code">outTemp</span>..</p>
|
|
<h4 class="config_option"><a name="Labels_ImperialFormats">[[ImperialFormats]]</a></h4>
|
|
<p>This sub-section is used to specify what format to be used for y-axis labels
|
|
in image plots that use Imperial (U.S.) units. It is also used for unit labels in
|
|
HTML file generation. For example, the options</p>
|
|
<p class="tty">outTemp = %.1f</p>
|
|
<p class="tty">rain = %.2f</p>
|
|
<p>would cause the given formats to be used when formatting outside temperature
|
|
and rain axes, respectively. The
|
|
<a href="http://docs.python.org/library/string.html#format-specification-mini-language">
|
|
formatting codes are those used by Python</a>, and are very similar to C's sprintf()
|
|
codes.</p>
|
|
<h4 class="config_option"><a name="Labels_ImperialUnits">[[ImperialUnits]]</a></h4>
|
|
<p>This sub-section specifies what unit labels to be used for the y-axis in image
|
|
plots that use Imperial (U.S.) units. For example, the options</p>
|
|
<p class="tty">outTemp = \xb0F</p>
|
|
<p class="tty">rain = ' in'</p>
|
|
<p>would cause outside temperature to have unit labels '<span class="code">°F</span>'
|
|
and rain to have labels '<span class="code"> in</span>'. (NB: the code
|
|
<span class="code">\xb0</span> is the hexadecimal value <span class="code">b0</span>,
|
|
which in many encodings encodes the degree sign.)</p>
|
|
<h3 class="config_section">[HTML]</h3>
|
|
<p>Section [HTML] has two options and two sub-sections. For additional information
|
|
on HTML generation <a href="#HTML_Generation">see the section below</a>.</p>
|
|
<h4 class="config_option">template_root</h4>
|
|
<p>This option specifies the directory, relative to <span class="code"><em>WEEWX_ROOT</em></span>,
|
|
where the HTML templates can be found. Required. No default.</p>
|
|
<h4 class="config_option">html_root</h4>
|
|
<p>This option specifies the directory, relative to <span class="code"><em>WEEWX_ROOT</em></span>,
|
|
where the generated HTML files should be put. Required. No default.</p>
|
|
<h4 class="config_option"><a name="HTML_ImperialUnits">[[ImperialUnits]]</a></h4>
|
|
<p>This subsection is similar to its eponymous counterpart in section
|
|
<span class="code">[Labels]</span> above, except it is used for HTML generation.
|
|
It is useful to have a separate section because HTML uses special 'entity' codes
|
|
to code special characters, such as the degree sign. For example, the options</p>
|
|
<p class="tty">outTemp = &deg;F</p>
|
|
<p class="tty">rain = ' in'</p>
|
|
<p>would cause outside temperature and rain to have unit labels '<span class="code">°F</span>'
|
|
and '<span class="code"> in</span>', respectively.</p>
|
|
<h4 class="config_option"><a name="HTML_Time">[[Time]]</a></h4>
|
|
<p>This subsection is used for time labels in HTML generation. It uses
|
|
<a href="http://docs.python.org/library/datetime.html#strftime-behavior">strftime()</a>
|
|
formats. For example</p>
|
|
<p class="tty">week = %H:%M on %A</p>
|
|
<p class="tty">month = %d-%b-%Y %H:%M</p>
|
|
<p>would specify that week data should use a format such as "<span class="code">15:20
|
|
on Sunday</span>", while month data should look like "<span class="code">06-Oct-2009
|
|
15:20</span>"</p>
|
|
<h1>7. <a name="Running_weewx">Running <span class="code">weewx</span></a></h1>
|
|
<p><span class="code">Weewx</span> can be run either from the command line (useful
|
|
for diagnostic purposes because it will print out a summary of every LOOP data),
|
|
or as a daemon. When first trying <span class="code">weewx</span>, it's probably
|
|
best to run it from the command line because you will be able to see command line
|
|
diagnostics, as well as log messages.</p>
|
|
<h2>7.1 Running from the command line</h2>
|
|
<p><span class="code">Weewx</span> can easily be run from the command line. Start
|
|
by making sure you have appropriate permissions to the serial port your weather
|
|
station uses. For example, if you are using a plain old serial port:</p>
|
|
<p class="tty">sudo chmod 666 /dev/ttyS0</p>
|
|
<p>Then run the main loop program, <span class="code">weewxd.py</span>, giving the
|
|
configuration file as its only parameter:</p>
|
|
<p class="tty"><em>$WEEWX_ROOT</em>/bin/weewxd.py <em>$WEEWX_ROOT</em>/weewx.conf</p>
|
|
<p>It should start by downloading any archive data from your weather station into
|
|
the database <span class="code"><em>$WEEWX_ROOT</em>/archive/weewx.sdb</span>. As
|
|
the Davis VantagePro can store a couple thousand archive records internally, this
|
|
could take a minute or two. I've found this process particularly slow on SuSE for
|
|
some reason.</p>
|
|
<p><span class="code">Weewx</span> will then start monitoring LOOP data, printing
|
|
a short version of the received data on standard output, about once every two seconds.</p>
|
|
<h2>7.2 <a name="Running_as_a_daemon">Running as a daemon</a></h2>
|
|
<p>First, select the appropriate run script. They can be found under
|
|
<span class="code"><em>$WEEWX_ROOT</em>/start_script</span>. </p>
|
|
<table style="width: 100%" class="indent">
|
|
<tr>
|
|
<td>SuSE:</td>
|
|
<td class="code"><em>$WEEWX_ROOT</em>/start_script/SuSE/weewx</td>
|
|
</tr>
|
|
<tr>
|
|
<td>Debian/Ubuntu:</td>
|
|
<td class="code"> <em>$WEEWX_ROOT</em>/start_script/Debian/weewx</td>
|
|
</tr>
|
|
</table>
|
|
<p>Check the chosen script to make sure the variable <span class="code">WEEWX_ROOT</span>
|
|
inside has been set to the proper root directory for your <span class="code">weewx</span>
|
|
installation (it should have been set to the correct value automatically by the
|
|
install process, but it's worth checking). </p>
|
|
<p>Copy it to the proper location for your system:</p>
|
|
<table style="width: 100%" class="indent">
|
|
<tr>
|
|
<td>SuSE:</td>
|
|
<td class="code">cp <em>$WEEWX_ROOT</em>/start_script/SuSE/weewx /etc/init.d</td>
|
|
</tr>
|
|
<tr>
|
|
<td>Debian/Ubuntu:</td>
|
|
<td class="code">cp <em>$WEEWX_ROOT</em>/start_script/Debian/weewx /etc/init.d</td>
|
|
</tr>
|
|
</table>
|
|
<p>Make sure the script is executable </p>
|
|
<table style="width: 100%" class="indent">
|
|
<tr>
|
|
<td>SuSE:</td>
|
|
<td class="code">chmod +x /etc/init.d/weewx</td>
|
|
</tr>
|
|
<tr>
|
|
<td>Debian/Ubuntu:</td>
|
|
<td class="code">chmod +x /etc/init.d/weewx</td>
|
|
</tr>
|
|
</table>
|
|
<p>Create symbolic links in the run level directories:</p>
|
|
<table style="width: 100%" class="indent">
|
|
<tr>
|
|
<td>SuSE:</td>
|
|
<td class="code">/usr/lib/lsb/install_initd /etc/init.d/weewx</td>
|
|
</tr>
|
|
<tr>
|
|
<td>Debian/Ubuntu:</td>
|
|
<td class="code">update-rc.d weewx defaults 98</td>
|
|
</tr>
|
|
</table>
|
|
<p><span class="code">Weewx</span> will now start automatically whenever your system
|
|
is booted. You can also manually start, stop, and restart the <span class="code">
|
|
weewx</span> daemon:</p>
|
|
<p class="tty">/etc/init.d/weewx start</p>
|
|
<p class="tty">/etc/init.d/weewx stop</p>
|
|
<p class="tty">/etc/init.d/weewx restart</p>
|
|
<p>By default, the scripts are designed to have <span class="code">weewx</span>
|
|
run at run levels 2, 3, 4 and 5. Incidentally, a nice tool for setting run levels
|
|
with Debian (Ubuntu) systems is <a href="http://sysv-rc-conf.sourceforge.net/">sysv-rc-conf</a>.
|
|
It uses a curses interface to allow you to change easily which run level any of
|
|
your daemons runs at. There is a similar tool on SuSE. From the start menu run the
|
|
YAST Control Center, then look for Systesm Services (Runlevel). Pick "Expert" mode
|
|
to see the run levels.</p>
|
|
<h1>8. <a name="Compatibility_with_wview">Compatibility with <span class="code">
|
|
wview</span></a></h1>
|
|
<p>The sqlite3 archive database used by <span class="code">weewx</span> (nominally,
|
|
<span class="code">weewx.sdb</span>) is completely compatible with the database
|
|
used by <a href="http://www.wviewweather.com">wview</a> (usually called
|
|
<span class="code">wview-archive.sdb</span>), at least as of Version 5.2.X. The
|
|
schema and its semantics is identical. However, the statistical file
|
|
<span class="code">stats.sdb</span> is different, and must be rebuilt</p>
|
|
<h1>9. <a name="HTML_Generation">HTML Generation</a></h1>
|
|
<p>HTML generation is done using the <a href="http://www.cheetahtemplate.org/">Cheetah</a>
|
|
templating engine. This is a very powerful engine, which essentially lets you have
|
|
the full semantics of Python available in your templates. As this would make the
|
|
templates incomprehensible to anyone but a Python programmer, <span class="code">
|
|
weewx</span> adopts a very small subset of its power. </p>
|
|
<p>Generally, any value is specified by using a 'dot' code. For example:</p>
|
|
<p class="tty">$month.outTemp.max</p>
|
|
<p class="tty">$month.outTemp.maxtime</p>
|
|
<p class="tty">$current.outTemp</p>
|
|
<p>would code the max outside temperature for the month, the time it occurred, and
|
|
the current outside temperature, respectively. So, an HTML file that looks like</p>
|
|
<p class="tty"><html></p>
|
|
<p class="tty"> <head></p>
|
|
<p class="tty"> <title>Current conditions</title></p>
|
|
<p class="tty"> </head></p>
|
|
<p class="tty"> <body></p>
|
|
<p class="tty"> <p>Current temperature = $current.outTemp</p></p>
|
|
<p class="tty"> <p>Max for the month is $month.outTemp.max, which occurred at</p>
|
|
<p class="tty">$month.outTemp.maxtime</p></p>
|
|
<p class="tty"> </body></p>
|
|
<p class="tty"></html></p>
|
|
<p>would be all you need for a very simple HTML page that would display the text:
|
|
</p>
|
|
<p class="indent">Current temperature = 51.0°F<br />
|
|
Max for the month is 68.8°F, which occurred at 07-Oct-2009 15:15</p>
|
|
<p>The format that was used to format the temperature (<span class="code">51.0</span>)
|
|
is specified in section <span class="code"><a href="#Labels_ImperialFormats">[Labels][[ImperialFormats]]</a></span>.
|
|
The unit label <span class="code">°F</span> is from section <span class="code">
|
|
<a href="#HTML_ImperialUnits">[HTML][[ImperialUnits]]</a></span>, while the time
|
|
format is from <span class="code"><a href="#HTML_Time">[HTML][[Time]]</a></span>.</p>
|
|
<p>The "dot" code has up to three parts. </p>
|
|
<ol>
|
|
<li>The first part is the time period, and can be one of <span class="code">
|
|
current</span>, <span class="code">day</span>, <span class="code">week</span>,
|
|
<span class="code">month</span>, <span class="code">year</span>, or
|
|
<span class="code">rainyear</span>.</li>
|
|
<li>The second part is the "SQL" type. This is something like '<span class="code">outTemp</span>',
|
|
'<span class="code">rain</span>', '<span class="code">wind</span>', etc. It
|
|
is called the "SQL" type because the identifier is identical to that used in
|
|
the schema of the SQL databases with three exceptions. First, type '<span class="code">wind</span>'
|
|
is a special hybrid type and does not appear in the SQL database. It brings
|
|
together the several different SQL types '<span class="code">windSpeed</span>',
|
|
'<span class="code">windDir</span>', <span class="code">windGust</span>', and
|
|
'<span class="code">windGustDir</span>' under one roof (all are still available,
|
|
should you wish to use them for a specialized application). Exceptions number
|
|
two and three are '<span class="code">heatdeg</span>' and '<span class="code">cooldeg</span>',
|
|
heating and cooling degree-days, respectively, which are synthesized from average
|
|
outside temperature and do not appear directly in the database.</li>
|
|
<li>The last position is the aggregation type, available for any time period
|
|
except for '<span class="code">current</span>'. The table below shows what aggregation
|
|
types are available for which types. </li>
|
|
</ol>
|
|
<h2>9.1 Types</h2>
|
|
<p>The following types are available to be used in your template (assuming your
|
|
station supports them and you have specified that it be stored in your stats database.
|
|
See section <a href="#stats_types">stats_types</a> in the <span class="code">weewx.conf</span>
|
|
configuration file).</p>
|
|
<table style="width: 100%">
|
|
<tr>
|
|
<td><em>Type</em></td>
|
|
<td class="code">min</td>
|
|
<td class="code">mintime</td>
|
|
<td class="code">max</td>
|
|
<td class="code">maxtime</td>
|
|
<td class="code">avg</td>
|
|
<td class="code">sum</td>
|
|
<td class="code">rms</td>
|
|
<td class="code">vecavg</td>
|
|
<td class="code">vecdir</td>
|
|
</tr>
|
|
<tr>
|
|
<td class="code">barometer</td>
|
|
<td>X</td>
|
|
<td>X</td>
|
|
<td>X</td>
|
|
<td>X</td>
|
|
<td>X</td>
|
|
<td> </td>
|
|
<td> </td>
|
|
<td> </td>
|
|
<td> </td>
|
|
</tr>
|
|
<tr>
|
|
<td class="code">inTemp</td>
|
|
<td>X</td>
|
|
<td>X</td>
|
|
<td>X</td>
|
|
<td>X</td>
|
|
<td>X</td>
|
|
<td> </td>
|
|
<td> </td>
|
|
<td> </td>
|
|
<td> </td>
|
|
</tr>
|
|
<tr>
|
|
<td class="code">outTemp</td>
|
|
<td>X</td>
|
|
<td>X</td>
|
|
<td>X</td>
|
|
<td>X</td>
|
|
<td>X</td>
|
|
<td> </td>
|
|
<td> </td>
|
|
<td> </td>
|
|
<td> </td>
|
|
</tr>
|
|
<tr>
|
|
<td class="code">inHumidity</td>
|
|
<td>X</td>
|
|
<td>X</td>
|
|
<td>X</td>
|
|
<td>X</td>
|
|
<td>X</td>
|
|
<td> </td>
|
|
<td> </td>
|
|
<td> </td>
|
|
<td> </td>
|
|
</tr>
|
|
<tr>
|
|
<td class="code">outHumidity</td>
|
|
<td>X</td>
|
|
<td>X</td>
|
|
<td>X</td>
|
|
<td>X</td>
|
|
<td>X</td>
|
|
<td> </td>
|
|
<td> </td>
|
|
<td> </td>
|
|
<td> </td>
|
|
</tr>
|
|
<tr>
|
|
<td class="code">wind</td>
|
|
<td>X</td>
|
|
<td>X</td>
|
|
<td>X</td>
|
|
<td>X</td>
|
|
<td>X</td>
|
|
<td> </td>
|
|
<td>X</td>
|
|
<td>X</td>
|
|
<td>X</td>
|
|
</tr>
|
|
<tr>
|
|
<td class="code">rain</td>
|
|
<td>X</td>
|
|
<td>X</td>
|
|
<td>X</td>
|
|
<td>X</td>
|
|
<td>X</td>
|
|
<td>X</td>
|
|
<td> </td>
|
|
<td> </td>
|
|
<td> </td>
|
|
</tr>
|
|
<tr>
|
|
<td class="code">dewpoint</td>
|
|
<td>X</td>
|
|
<td>X</td>
|
|
<td>X</td>
|
|
<td>X</td>
|
|
<td>X</td>
|
|
<td> </td>
|
|
<td> </td>
|
|
<td> </td>
|
|
<td> </td>
|
|
</tr>
|
|
<tr>
|
|
<td class="code">windchill</td>
|
|
<td>X</td>
|
|
<td>X</td>
|
|
<td>X</td>
|
|
<td>X</td>
|
|
<td>X</td>
|
|
<td> </td>
|
|
<td> </td>
|
|
<td> </td>
|
|
<td> </td>
|
|
</tr>
|
|
<tr>
|
|
<td class="code">heatindex</td>
|
|
<td>X</td>
|
|
<td>X</td>
|
|
<td>X</td>
|
|
<td>X</td>
|
|
<td>X</td>
|
|
<td> </td>
|
|
<td> </td>
|
|
<td> </td>
|
|
<td> </td>
|
|
</tr>
|
|
<tr>
|
|
<td class="code">heatdeg</td>
|
|
<td> </td>
|
|
<td> </td>
|
|
<td> </td>
|
|
<td> </td>
|
|
<td> </td>
|
|
<td>X</td>
|
|
<td> </td>
|
|
<td> </td>
|
|
<td> </td>
|
|
</tr>
|
|
<tr>
|
|
<td class="code">cooldeg</td>
|
|
<td> </td>
|
|
<td> </td>
|
|
<td> </td>
|
|
<td> </td>
|
|
<td> </td>
|
|
<td>X</td>
|
|
<td> </td>
|
|
<td> </td>
|
|
<td> </td>
|
|
</tr>
|
|
<tr>
|
|
<td class="code">ET</td>
|
|
<td>X</td>
|
|
<td>X</td>
|
|
<td>X</td>
|
|
<td>X</td>
|
|
<td>X</td>
|
|
<td> </td>
|
|
<td> </td>
|
|
<td> </td>
|
|
<td> </td>
|
|
</tr>
|
|
<tr>
|
|
<td class="code">radiation</td>
|
|
<td>X</td>
|
|
<td>X</td>
|
|
<td>X</td>
|
|
<td>X</td>
|
|
<td>X</td>
|
|
<td> </td>
|
|
<td> </td>
|
|
<td> </td>
|
|
<td> </td>
|
|
</tr>
|
|
<tr>
|
|
<td class="code">UV</td>
|
|
<td>X</td>
|
|
<td>X</td>
|
|
<td>X</td>
|
|
<td>X</td>
|
|
<td>X</td>
|
|
<td> </td>
|
|
<td> </td>
|
|
<td> </td>
|
|
<td> </td>
|
|
</tr>
|
|
<tr>
|
|
<td class="code">extraTemp1<br />
|
|
extraTemp2<br />
|
|
extraTemp3</td>
|
|
<td>X</td>
|
|
<td>X</td>
|
|
<td>X</td>
|
|
<td>X</td>
|
|
<td>X</td>
|
|
<td> </td>
|
|
<td> </td>
|
|
<td> </td>
|
|
<td> </td>
|
|
</tr>
|
|
<tr>
|
|
<td class="code">soilTemp1<br />
|
|
soilTemp2<br />
|
|
soilTemp3</td>
|
|
<td>X</td>
|
|
<td>X</td>
|
|
<td>X</td>
|
|
<td>X</td>
|
|
<td>X</td>
|
|
<td> </td>
|
|
<td> </td>
|
|
<td> </td>
|
|
<td> </td>
|
|
</tr>
|
|
<tr>
|
|
<td class="code">leafTemp1<br />
|
|
leafTemp2</td>
|
|
<td>X</td>
|
|
<td>X</td>
|
|
<td>X</td>
|
|
<td>X</td>
|
|
<td>X</td>
|
|
<td> </td>
|
|
<td> </td>
|
|
<td> </td>
|
|
<td> </td>
|
|
</tr>
|
|
<tr>
|
|
<td class="code">extraHumid1<br />
|
|
extraHumid2</td>
|
|
<td>X</td>
|
|
<td>X</td>
|
|
<td>X</td>
|
|
<td>X</td>
|
|
<td>X</td>
|
|
<td> </td>
|
|
<td> </td>
|
|
<td> </td>
|
|
<td> </td>
|
|
</tr>
|
|
<tr>
|
|
<td class="code">soilMoist1<br />
|
|
soilMoist2<br />
|
|
soilMoist3<br />
|
|
soilMoist4</td>
|
|
<td>X</td>
|
|
<td>X</td>
|
|
<td>X</td>
|
|
<td>X</td>
|
|
<td>X</td>
|
|
<td> </td>
|
|
<td> </td>
|
|
<td> </td>
|
|
<td> </td>
|
|
</tr>
|
|
<tr>
|
|
<td class="code">leafWet1<br />
|
|
leafWet2</td>
|
|
<td>X</td>
|
|
<td>X</td>
|
|
<td>X</td>
|
|
<td>X</td>
|
|
<td>X</td>
|
|
<td> </td>
|
|
<td> </td>
|
|
<td> </td>
|
|
<td> </td>
|
|
</tr>
|
|
<tr>
|
|
<td class="code">rxCheckPercent</td>
|
|
<td>X</td>
|
|
<td>X</td>
|
|
<td>X</td>
|
|
<td>X</td>
|
|
<td>X</td>
|
|
<td> </td>
|
|
<td> </td>
|
|
<td> </td>
|
|
<td> </td>
|
|
</tr>
|
|
</table>
|
|
<h1>10. <a name="Monitoring_weewx">Monitoring <span class="code">weewx</span></a></h1>
|
|
<p><span class="code">Weewx</span> logs many events to the system log. On Debian
|
|
systems, this is <span class="code">/var/log/syslog</span>, on SuSE,
|
|
<span class="code">/var/log/messages</span>. Your system may use yet another place.
|
|
When troubleshooting the system, be sure to check it!</p>
|
|
<p>Setting the option <span class="code">debug </span>in <span class="code">weewx.conf</span>
|
|
to <span class="code">1</span> (one) will generate many more checks and output and
|
|
can be useful for debugging.</p>
|
|
<h1>11. <a name="Architectural_notes">Architectural notes</a></h1>
|
|
<h2>11.1 Goals</h2>
|
|
<p>The primary goals of <span class="code">weewx </span>are:</p>
|
|
<ul>
|
|
<li>Architectural simplicity. No semaphores, no named pipes, no inter-process
|
|
communications, no complex multi-threading to manage. </li>
|
|
<li>One code base. The same code base should be used for all platforms and any
|
|
combination of features. Ample configuration options should be provided so the
|
|
user doesn't feel tempted to start hacking code. At worse, the user may have
|
|
to subclass, which is much easier to port to newer versions of the code base.</li>
|
|
<li>Minimal reliance on external packages, so the user doesn't have to go chase
|
|
them down all over the Web.</li>
|
|
<li>"Fast enough." In any design decision, architectural simplicity trumps speed.
|
|
</li>
|
|
<li>Support only the Davis VantagePro2 initially (that's what I have), but make
|
|
no architectural decisions that lock out other stations.</li>
|
|
<li>As "pythonic" as I know how to make it. I'm a beginner Python programmer
|
|
with two decades of experience in C++. I tried hard to not make the code base
|
|
look like it was written by a C++ programmer who stumbled across a Python manual!</li>
|
|
</ul>
|
|
<h2>11.2 Strategies</h2>
|
|
<p>To meet these goals, the following strategies were used:</p>
|
|
<ul>
|
|
<li>A powerful configuration parser,
|
|
<a href="http://www.voidspace.org.uk/python/configobj.html">ConfigObj</a>, by
|
|
Michael Foord and Nicola Larosa, was chosen to read the configuration file.
|
|
This allows many options that might otherwise have to go in the code to go instead
|
|
in a configuration file.</li>
|
|
<li>A powerful templating engine, <a href="http://www.cheetahtemplate.org/">
|
|
Cheetah</a>, was used. This allows many variables that I may not have thought
|
|
of to be accessed from within the HTML templates, without starting to modify
|
|
the code.</li>
|
|
<li>A largely stateless design style. For example, many of the processing routines
|
|
read their own data from the database, rather than caching it and sharing with
|
|
other processing routines. While this means the same data may be read multiple
|
|
times, it also means the only point of possible cache incoherence is through
|
|
the database, where transactions are easily controlled. This greatly reduces
|
|
the chances of corrupting the data, making it much easier to understand and
|
|
modify the code base.</li>
|
|
<li>No static variables (except read only variables) to make it easy to simultaneously
|
|
support multiple weather stations and to allow some level of multithreading.</li>
|
|
<li>Pure Python. The code base is 100% Python — no underlying C libraries need
|
|
be built to install <span class="code">weewx</span>. </li>
|
|
</ul>
|
|
<p>While <span class="code">weewx </span>is nowhere near as fast at generating images
|
|
and HTML as its predecessor, <span class="code">wview </span>(this is partially
|
|
because it uses fancier fonts and a way more powerful templating engine), it is
|
|
'fast enough' for all platforms but the slowest. I run it regularly on a 500 MHz
|
|
machine where generating the 9 images used in the "Current Conditions" page takes
|
|
just under 2 seconds. Compare this with <span class="code">wview</span>'s 0.4 seconds.</p>
|
|
<p>Unfortunately, the architectural goal of one code base is likely to be broken
|
|
with the arrival of Python V3.X. It has so many changes that are not backwards compatible
|
|
with V2.X, that a separate code base will most likely be needed. My intention is
|
|
to stick with the V2.5 and V2.6 versions until V3.X is so widespread it cannot be
|
|
ignored, then make a permanent switch. I doubt this will affect the average
|
|
<span class="code">weewx</span> user. </p>
|
|
<h2>11.3 Run time internals</h2>
|
|
<p>Three threads are used within <span class="code">weewx</span>:</p>
|
|
<ol>
|
|
<li>The main thread of the program is used to monitor the VantagePro and, by
|
|
definition, is active the entire lifetime of the program. All interactions with
|
|
the hardware go through it. On program startup, the main thread starts by downloading
|
|
any data from the VP that has been stored on board, but not yet put in the
|
|
<span class="code">weewx</span> archive database. If the statistical database
|
|
doesn't exist (nominally located at <span class="code"><em>$WEEWX_ROOT</em>/archive/stats.sdb</span>),
|
|
or is out of date, then it will repopulate the missing data from the main database.
|
|
Finally, it sets up a thread (thread #2 below) to publish data to the Weather
|
|
Underground (WU) and other sites that interact through HTTP.
|
|
<p>Once finished with these startup chores, the main thread then puts the VantagePro
|
|
in LOOP mode. In this mode, the VP offers up data every 2 seconds, sleeping
|
|
in between. This is a very energy saving mode. The thread monitors the port
|
|
and when new data is available, it adds it to the running statistical tally,
|
|
in particular highs, lows, and wind rms data, kept in the stats database. While
|
|
in LOOP mode, very little processing is done so it doesn't miss any updates.</p>
|
|
<p>When an archive interval is due, typically every 5 minutes or so, then the
|
|
main thread cancels the LOOP mode, and then downloads the new archive data,
|
|
putting it in the main database. It also uses the archive data to update averages
|
|
in the stats database. It puts the new record in a Queue to be sent to the Weather
|
|
Underground. It then creates and starts thread #3 to do any processing of the
|
|
data.</p>
|
|
</li>
|
|
<li>
|
|
<p>Thread #2 interacts with the Weather Underground. It is also active the entire
|
|
lifetime of the program. It monitors a Queue. When new data appears in the Queue,
|
|
this thread forms the necessary URL to send it to the WU and then sends it.
|
|
It then goes back to monitoring the queue. This way, posting data on the WU
|
|
can happen asynchronously with other processing.</p>
|
|
</li>
|
|
<li>
|
|
<p>Thread #3 is responsible for generating HTML files, images, and NOAA monthly
|
|
and yearly reports. Its lifetime is only as long as it takes to process a new
|
|
archive record and then it dies. Because most of the tricky processing happens
|
|
in this thread, this is the most likely place where an exception could occur.
|
|
However, should this happen, it will only affect this short-lived thread, and
|
|
not the much longer-lived main thread. Hopefully, this means that at least no
|
|
data will be missed.</p>
|
|
</li>
|
|
</ol>
|
|
<p>All writes to the databases are protected by transactions. You can kill the program
|
|
at any time (either Control-C if run from the command line or "<span class="code">/etc/init.d/weewx
|
|
stop</span>" if a daemon) without fear of corrupting the databases.</p>
|
|
<p>The code makes ample use of exceptions to insure graceful recovery from problems
|
|
such as network outages. It also monitors socket and console timeouts, restarting
|
|
whatever it was working on several times before giving up. In the case of an unrecoverable
|
|
console error (such as the console not responding at all), the program waits 60
|
|
seconds then restarts the program from the top.</p>
|
|
<p>Any "hard" exceptions, that is those that do not involve network and console
|
|
timeouts and are most likely due to a logic error, are logged, reraised, and ultimately
|
|
cause thread termination. If this happens in the main thread (not likely and hasn't
|
|
happened to me yet), then this causes program termination.</p>
|
|
<h2>11.4 Terminology</h2>
|
|
<p>This is a glossary of terminology used throughout the code.</p>
|
|
<table style="width: 100%">
|
|
<tr>
|
|
<td>packet</td>
|
|
<td>Something obtained off the weather station. Frequently uses a complex
|
|
internal encoding, so it requires some processing to be useful.</td>
|
|
</tr>
|
|
<tr>
|
|
<td>record</td>
|
|
<td>Something obtained off the SQL database. </td>
|
|
</tr>
|
|
<tr>
|
|
<td>archive packet</td>
|
|
<td>A packet obtained off the store on the weather station. For example,
|
|
with a Davis VantagePro, it's obtained using their <span class="code">DMPAFT</span>
|
|
command. </td>
|
|
</tr>
|
|
<tr>
|
|
<td>loop packet</td>
|
|
<td>A packet with the current observations. For example, with a Davis VantagePro,
|
|
it's obtained using their <span class="code">LOOP</span> command. </td>
|
|
</tr>
|
|
<tr>
|
|
<td>archive record</td>
|
|
<td>A record obtained off the SQL database</td>
|
|
</tr>
|
|
<tr>
|
|
<td>tuple-time</td>
|
|
<td>An instance of the Python object <span class="code">time.struct_time</span>.
|
|
This is a 9-wise tuple that represent a time. It could be in either local
|
|
time or UTC, though usually the former. See module <span class="code">time</span>
|
|
for more information. They are useful because they are a little closer in
|
|
format to what the Davis VantagePro uses, although they still require a
|
|
bit of processing. Variables carrying tuple time usually have a suffix '<span class="code">_tt</span>'.</td>
|
|
</tr>
|
|
<tr>
|
|
<td>epoch time</td>
|
|
<td>Sometimes referred to as "unix time," or "unix epoch time." The number
|
|
of seconds since the epoch, which is 1 Jan 1970 00:00:00 UTC. Hence, it
|
|
always represents UTC (well.... after adding a few leap seconds. But, close
|
|
enough). This is the time used on the sqlite archive and appears as type
|
|
'<span class="code">dateTime</span>' in the SQL schema, perhaps an unfortunate
|
|
name because of the similarity to the Python type 'datetime'. Very easy
|
|
to manipulate, but it's an opaque big number. </td>
|
|
</tr>
|
|
<tr>
|
|
<td>time stamp</td>
|
|
<td>A variable in unix epoch time. Always in UTC. Variables carrying a time
|
|
stamp usually have a suffix '<span class="code">_ts</span>'.</td>
|
|
</tr>
|
|
<tr>
|
|
<td>datetime</td>
|
|
<td>An instance of the Python object <span class="code">datetime.datetime</span>.
|
|
Variables of type datetime usually have a suffix '<span class="code">_dt</span>'.</td>
|
|
</tr>
|
|
</table>
|
|
<h2>11.5 Units</h2>
|
|
<p>This package is imperial (U.S.) units only. However, it has been set up to make
|
|
it easy to extend to metric. </p>
|
|
<p>In general, there are three different areas where the unit system makes a difference.:
|
|
</p>
|
|
<ol>
|
|
<li>On the weather station. As far as I know, the Davis VantagePro series supports
|
|
only imperial units internally. So, any translation to metric must be done in
|
|
one of the other two areas: </li>
|
|
<li>In the database. The unit system of any individual record is indicated by
|
|
the "usUnits" field. The numerical value 1 indicates imperial. Other numbers
|
|
haven't been assigned (yet). Right now, only imperial units is supported.
|
|
</li>
|
|
<li>In the presentation (i.e., html and image files). Right now, whatever unit
|
|
system is in use in the database is carried through. </li>
|
|
</ol>
|
|
<p>The transition from 1 to 2, i.e., from data in the VantagePro to the database,
|
|
is handled by a translation function. Right now, only one is supplied,
|
|
<span class="code">weewx.VantagePro.translateArchiveToImperial</span>. Others could
|
|
easily be introduced. </p>
|
|
<h2>11.6 Value "<span class="code">None</span>"</h2>
|
|
<p>The Python special value '<span class="code">None</span>' is used throughout
|
|
to signal a missing data point. All functions expect it.</p>
|
|
<p>However, the time value must never be '<span class="code">None</span>'. This
|
|
is because it is used as the primary key in the SQL database. </p>
|
|
<h2>11.7 Time</h2>
|
|
<p><span class="code">Weewx </span>stores all data in UTC (roughly, "Greenwich"
|
|
or "Zulu") time. However, usually one is interested in weather events in local time
|
|
and want image and HTML generation to reflect that. Furthermore, most weather stations
|
|
are configured in local time. This requires that many data times be converted back
|
|
and forth between UTC and local time. To avoid tripping up over time zones and daylight
|
|
savings time, <span class="code">weeewx</span> generally uses Python routines to
|
|
do this conversion. Nowhere in the code base is there any explicit recognition of
|
|
DST. Instead, its presence is implicit in the conversions. At times, this can cause
|
|
the code to be relatively inefficient. </p>
|
|
<p>For example, if one wanted to plot something every 3 hours in UTC time, it would
|
|
be very simple: to get the next plot point, just add 10,800 to the epoch time:</p>
|
|
<p class="tty">next_ts = last_ts + 10800</p>
|
|
<p>But, if one wanted to plot something for every 3 hours <em>in local time</em>
|
|
(that is, at 0000, 0300, 0600, etc.), despite a possible DST change in the middle,
|
|
one could modify the above to recognize whether a DST transition occurs sometime
|
|
between <span class="code">last_ts</span> and the next three hours and, if so, make
|
|
the necessary adjustments. This is generally what <span class="code">wview</span>
|
|
does. <span class="code">Weewx </span>takes a different approach and converts from
|
|
UTC to local, does the arithmetic, then converts back. This is inefficient, but
|
|
bulletproof against changes in DST algorithms, etc:</p>
|
|
<p class="tty">time_dt = datetime.datetime.fromtimestamp(last_ts)</p>
|
|
<p class="tty">delta = datetime.timedelta(seconds=10800)</p>
|
|
<p class="tty">next_dt = time_dt + delta</p>
|
|
<p class="tty">next_ts = int(time.mktime(next_dt.timetuple()))</p>
|
|
<p>Other time conversion problems are handled in a similar manner.</p>
|
|
<h1>12. <a name="Table_of_Tested_Versions">Table of Tested Versions</a></h1>
|
|
<p>Three different configurations were used to test weewx V1.1.X. Here are the package
|
|
versions used in each configuration:</p>
|
|
<table style="width: 75%" class="style1">
|
|
<tr>
|
|
<td><strong>Package</strong></td>
|
|
<td><strong>Configuration 1</strong></td>
|
|
<td><strong>Configuration 2</strong></td>
|
|
<td><strong>Configuration 3</strong></td>
|
|
</tr>
|
|
<tr>
|
|
<td>Python</td>
|
|
<td>V2.5.2</td>
|
|
<td>V2.5.4</td>
|
|
<td>V2.6.2</td>
|
|
</tr>
|
|
<tr>
|
|
<td>sqlite3</td>
|
|
<td>V3.5.9</td>
|
|
<td>V3.6.10</td>
|
|
<td>V3.6.10</td>
|
|
</tr>
|
|
<tr>
|
|
<td>pysqlite</td>
|
|
<td>V2.5.5</td>
|
|
<td>V2.5.5</td>
|
|
<td>V2.5.0</td>
|
|
</tr>
|
|
<tr>
|
|
<td>configobj</td>
|
|
<td>V4.6.0</td>
|
|
<td>V4.6.0</td>
|
|
<td>V4.6.0</td>
|
|
</tr>
|
|
<tr>
|
|
<td>pyserial</td>
|
|
<td>V1.35</td>
|
|
<td>V1.35</td>
|
|
<td>V1.35</td>
|
|
</tr>
|
|
<tr>
|
|
<td>Cheetah</td>
|
|
<td>V2.0.1</td>
|
|
<td>V2.0.1</td>
|
|
<td>V2.2.2</td>
|
|
</tr>
|
|
<tr>
|
|
<td>Python Imaging<br />
|
|
Library (PIL)</td>
|
|
<td>V1.1.6</td>
|
|
<td>V1.1.6</td>
|
|
<td>V1.1.6</td>
|
|
</tr>
|
|
</table>
|
|
|
|
</body>
|
|
|
|
</html>
|