mirror of
https://github.com/weewx/weewx.git
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1043 lines
57 KiB
HTML
1043 lines
57 KiB
HTML
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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<html xmlns="http://www.w3.org/1999/xhtml" xmlns:v="urn:schemas-microsoft-com:vml" xmlns:o="urn:schemas-microsoft-com:office:office">
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<!-- $Revision$ -->
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<!-- $Date$ -->
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<head>
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<meta http-equiv="Content-Language" content="en-us" />
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
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<title>The Weewx weather system</title>
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<style type="text/css">
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</style>
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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 1.6</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="#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
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notes</a></p>
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</li>
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</ol>
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<p>For information on customizing <span class="code">weewx</span>, see the
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separate document <a href="customizing.htm"><em>Customizing </em><em>
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<span class="code">weewx</span></em></a>.</p>
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<h1>1. <a name="Copyright">Copyright</a></h1>
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<p>(c) 2009, 2010 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><span class="code">weewx</span> is a piece of software, written in
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<a href="http://www.python.org">Python</a>, that interacts with your
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weather station to produce plots, reports, and HTML pages. It can
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optionally upload the reports to a remote Web server as well as publish to the <a href="http://www.wunderground.com">
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WeatherUnderground</a>. It uses modern software concepts, making it
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simple, robust, and easy to extend. For an example station see
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<a href="http://www.threefools.org/weewx">Hood River West</a>.</p>
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<p>I wrote <span class="code">weewx</span> over the winter of 2008-2009 for two reasons: it was a wet and
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miserable winter here in Oregon with not much else to do, so there was no good reason
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not to, and because I wanted a simple, easy-to-understand server to run my Davis
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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
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high-performance and feature rich system authored by Mark Teel
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with lots of users. Written in C, it's an efficient system that can run on very underpowered boxes. In exchange, it's huge
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(45,000+ lines of code), tightly integrated in with its companion library, radlib (another
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14,000+ lines), and very complex, making it difficult to understand and reliably
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customize. I wanted something more modern and much simpler.</p>
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<p>Having made a career in C++ and Java, I was also interested in some more
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modern languages, so I thought I'd try either Python or Ruby (although, truth be
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told, the roots of Python are nearly as old as C++!). I ended up picking Python because
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its libraries are more mature and there are many mores choices for third party
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libraries.</p>
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<p><span class="code">Weewx</span> weighs in at under 4,000 lines of code, plus
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another 2,500 comment lines. Because it is pure Python, it requires no makefiles,
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no builds, no special installs. However, to be fair, at this point it supports
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only the
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<a href="http://www.davisnet.com/weather/products/vantagepro.asp">Davis VantagePro2</a>
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weather station. On the other hand, it offers very powerful configuration
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and templating options, as well as an internally extensible engine, making it easy to customize.
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Its internal modular design and use of modern exception handling make it very
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robust and difficult to crash. It is also architecturally
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very simple and easy to 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 of sqlite, 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. However, some users
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have reported having to install PIL. In this case</p>
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<p class="tty">sudo apt-get install python-imaging</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>
|
|
<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 <span class="code">easy_install</span> has been installed, installing the rest of the packages is very easy.</p>
|
|
<h4>sqlite3</h4>
|
|
<p>My Ubuntu 8.10 system came with sqlite 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>
|
|
<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
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|
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
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|
means installing the gcc compiler. You may also have to install the sqlite3 development
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|
environment as well.</p>
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<p>With the development environment in place, you can easily build and install pysqlite:</p>
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<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>
|
|
<p class="tty">easy_install http://pysqlite.googlecode.com/files/pysqlite-2.5.5.tar.gz</p>
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<h4>configobj</h4>
|
|
<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>
|
|
<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 40MB 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%
|
|
Python with no "C" modules to compile, installing it is very easy. Furthermore,
|
|
it uses the standard Python <a href="http://docs.python.org/install/index.html">
|
|
distutils</a> install method, which is very easy and flexible. Detailed instructions
|
|
follow.</p>
|
|
<h2>5.1 Unpacking</h2>
|
|
<p>Start by unpack the tar ball (substitute your version for X.Y.Z) into any convenient
|
|
directory where you have write permission</p>
|
|
<p class="tty">tar xvf weewx-X.Y.Z</p>
|
|
<p>Then change directory into it:</p>
|
|
<p class="tty">cd weewx-X.Y.Z</p>
|
|
<h2>5.1 Choosing the <span class="code">WEEWX_ROOT</span> directory</h2>
|
|
<p>Next step is figuring out where you want to install <span class="code">weewx</span>.
|
|
If <span class="code"><em>WEEWX_ROOT</em></span> symbolizes the root location of
|
|
the <span class="code">weewx</span> directory hierarchy, then</p>
|
|
<ul>
|
|
<li><span class="code"><em>$WEEWX_ROOT</em>/bin</span> is where the Python packages
|
|
and scripts are installed;</li>
|
|
<li><span class="code"><em>$WEEWX_ROOT</em>/weewx.conf</span> is the configuration
|
|
file;</li>
|
|
<li><span class="code"><em>$WEEWX_ROOT</em>/skins</span> is where the skins live;</li>
|
|
<li><span class="code"><em>$WEEWX_ROOT</em>/archive</span> is the directory
|
|
where the sqlite3 databases live;</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>Before upgrading from a previous version of <span class="code">weewx</span>,
|
|
check the upgrade notes, found in file <a href="upgrading.htm">upgrading.htm</a>, to see if there any
|
|
specific actions you need to do. </p>
|
|
<p>You then generally follow the procedure above. </p>
|
|
<p><strong>In particular, before starting, be sure to set </strong>
|
|
<span class="code"><strong>home</strong></span><strong> in the file </strong> <span class="code">
|
|
<strong>setup.cfg</strong></span><strong>. </strong> </p>
|
|
<p>The build and install process will do the following for you.</p>
|
|
<ul>
|
|
<li>Save your old 'skin' subdirectory as <span class="code"><em>$WEEWX_ROOT</em>/skins.YYYYMMDDHHMMSS</span>
|
|
where YYYYMMDDHHMMSS is a timestamp;</li>
|
|
<li>Save your old 'bin' subdirectory as <span class="code"><em>$WEEWX_ROOT</em>/bin.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>$WEEWX_ROOT</em>/weewx.conf.YYYYMMDDHHMMSS</span>.</li>
|
|
</ul>
|
|
<h2>5.3 Permissions</h2>
|
|
<p>Strictly speaking it is not necessary to install or run <span class="code">weewx</span>
|
|
with root privileges. You only need read/write access to the serial port for your
|
|
hardware. For example, if your hardware has a USB interface, on Ubuntu and SuSE:</p>
|
|
<p class="tty">sudo chmod a+rw /dev/ttyUSB0</p>
|
|
<p>Once done, if you edit <span class="code">setup.cfg</span> to install into a
|
|
directory where you have write permissions, you can install and run
|
|
<span class="code">weewx</span> without any root privileges at all. </p>
|
|
<h2>5.4 Final note on installation</h2>
|
|
<p>Because <span class="code">weewx</span> is pure Python, it actually does not
|
|
have to be "built" and "installed" at all! You can just simply run it out of whatever
|
|
directory you unpack it into (after, of course, editing <span class="code">weewx.conf</span>
|
|
to reflect your local environment). I do this all the time when testing. However,
|
|
the <span class="code">setup.py</span> script does include special provisions for
|
|
updating your configuration file <span class="code">weewx.conf</span>, which can
|
|
be handy when upgrading to a later version.</p>
|
|
<h1>6. <a name="Configuring_weewx">Configuring <span class="code">weewx</span></a></h1>
|
|
<p>This section covers configuring your archive and statistical database (if necessary;
|
|
this step is required only if you are moving from
|
|
<a href="http://www.wviewweather.com/">wview</a> to <span class="code">weewx</span>), configuring your weather
|
|
station, and configuring the configuration files <span class="code">weewx.conf</span>
|
|
and <span class="code">skin.conf</span>.</p>
|
|
<p>In the following, <span class="code"><em>$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>NOTE: 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>If you wish to transfer your wview data, note that 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 <span class="code">weewx</span> use identical schema for the first of these (the archive
|
|
database), it can be just copied over. However, the second (the statistical databases)
|
|
is different — the <span class="code">weewx</span> 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 Slim</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 nominally every four hours (changeable by the user). You should run a
|
|
<a href="http://www.ntp.org/">NTP</a> 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 $WEEWX_ROOT/weewx.conf</p>
|
|
<h2>6.3 Editing the configuration file <span class="code">weewx.conf</span></h2>
|
|
<p>Station specific information is set in the configuration file
|
|
<span class="code"><em>$WEEWX_ROOT</em>/weewx.conf</span>. There is another
|
|
configuration file <span class="code">skin.conf</span> for presentation-specific
|
|
options, which is described in the <em><a href="customizing.htm">Customizing</a></em>
|
|
document under section <em>
|
|
<a href="customizing.htm#Reference:_The_Standard_skin_configuration_file">
|
|
Reference: The standard skin configuration file</a></em>.</p>
|
|
<p>Most of the important
|
|
options 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 UTF-8 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 the same units specified in
|
|
<span class="code"><a href="customizing.htm#group_altitude">group_altitude</a></span>. 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_option"><span class="config_important">heating_base<br />
|
|
cooling_base</span></h4>
|
|
<p>Set to the base temperature for calculating heating and cooling degree-days,
|
|
respectively, in the same units specified in <span class="code">
|
|
<a href="customizing.htm#group_temperature">group_temperature</a></span>. The default is 65.0 for both.</p>
|
|
<h4 class="config_option">week_start</h4>
|
|
<p>Start of the week. 0=Monday, 1= Tuesday, ... , 6 = Sunday. Default is 6
|
|
(Sunday)</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
|
|
(<em>i.e.</em>, 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 change it, this value should be left at 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' (U.S. Customary) or '2' (Metric). As far as I know, all Davis instruments support
|
|
only U.S.. In any case, U.S. is the only system supported by
|
|
<span class="code">weewx</span> at this time. Default is 1.</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 in 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 U.S. Customary system</p>
|
|
<h3 class="config_section"><a name="[Stats]">[Stats]</a></h3>
|
|
<p>This section is for configuring the sqlite3 database in 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"><a name="[Reports]">[Reports]</a></h3>
|
|
<p>This section controls which reports are to be generated. While it can be
|
|
highly customized for your individual situation, this documentation describes
|
|
the section as shipped in the standard distribution.</p>
|
|
<p>Each report is represented by a sub-section, marked with double brackets (<em>e.g.</em>,
|
|
<span class="code">[[MyReport]]</span>). Any options for the report should be
|
|
placed under it. The standard report service will go through the sections,
|
|
running each report in order. Hence, for the stock distribution, report
|
|
<span class="code">[[StandardReport]]</span> will be run first, then report
|
|
<span class="code">[[FTP]]</span> (which actually optionally uploads the results
|
|
to a remote web server). Details for how to customize reports are in the section
|
|
<em><a href="customizing.htm#Opportunities_for_customizing_reports">
|
|
Opportunities for customizing reports</a></em>, in the separate <em>
|
|
<a href="customizing.htm">Customizing</a></em> document.</p>
|
|
<p class="config_option">SKIN_ROOT</p>
|
|
<p>The directory relative to <span class="code"><em>$WEEWX_ROOT</em></span>
|
|
where the skins live. Default is <span class="code">skins</span>.</p>
|
|
<p class="config_option">HTML_ROOT</p>
|
|
<p>The target directory for the generated files, relative to <span class="code">
|
|
<em>$WEEWX_ROOT</em></span>. Generated files and images will be put here.
|
|
Default is <span class="code">public_html</span>.</p>
|
|
<h4 class="config_section">[[StandardReport]]</h4>
|
|
<p>This is the standard report that will be run on every archiving interval. It
|
|
uses the skin "<span class="code">Standard</span>", which generates four HTML
|
|
pages ("day", "week", "month", and "year" observations), plot images for same,
|
|
and NOAA monthly and yearly reports. Unless changed otherwise, it uses US
|
|
Customary Units and puts the results in <span class="code">public_html</span>
|
|
and subdirectory <span class="code">public_html/NOAA</span>.</p>
|
|
<h4 class="config_section">[[FTP]]</h4>
|
|
<p>While this "report" doesn't actually generate anything, it uses the report
|
|
machinery to upload files from directory <span class="code"><em>$HTML_ROOT</em></span>
|
|
to a remote webserver. It does an incremental update,
|
|
that is, it only FTPs any files that have changed, saving the outgoing bandwidth
|
|
of 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_tries</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">[Engines]</h3>
|
|
<p>This section is used to configure the internal service engine in weewx. It is
|
|
for advanced customization. Details on how to do this is found in the <em>
|
|
<a href="customizing.htm">Customizing</a></em> document under the section <em>
|
|
<a href="customizing.htm#Customizing_the_weewx_service_engine">Customizing the
|
|
weewx service engine</a></em>.</p>
|
|
<h4 class="config_section">[[WxEngine]]</h4>
|
|
<p>This section is for options used by the service engine.</p>
|
|
<pre>service_list</pre>
|
|
<p>This option is the list of <em>services</em> that are to be run by the
|
|
service engine. After each event (such as the arrival of LOOP data, etc.), they
|
|
will be run in the given order. </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>
|
|
<p>You can tell a running instance of <span class="code">weewx</span> to reread
|
|
its configuration file by sending it the <span class="code">HUP</span> signal.
|
|
First run <span class="code">ps</span> to find out the Process ID (PID) number
|
|
of the instance, then send it the <span class="code">HUP</span> signal:</p>
|
|
<p class="tty">ps -a # Note the
|
|
PID of the weewxd.py process</p>
|
|
<p class="tty">kill -HUP <em>pid</em> # Send it a HUP signal</p>
|
|
<h2>7.2 <a name="Running_as_a_daemon">Running as a daemon</a></h2>
|
|
<p>For unattended operations it is best to have <span class="code">weewx</span>
|
|
run as a daemon, started automatically when the server is rebooted. Start by selecting 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 Systems Services (Runlevel). Pick "Expert" mode
|
|
to see the run levels.</p>
|
|
<p>You can also tell <span class="code">weewx</span> to reread its configuration
|
|
file without stopping by using the 'reload' option:</p>
|
|
<p class="tty">/etc/init.d/weewx reload</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 wview 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="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>10. A<a name="Architectural_notes">rchitectural notes</a></h1>
|
|
<p>This section is not needed to get started. </p>
|
|
<h2>10.1 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, all
|
|
weather stations, all platforms, and any combination of features. Ample
|
|
configuration and customization 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,
|
|
than customizing the base code.</li>
|
|
<li>Minimal reliance on external packages, so the user doesn't have to go chase
|
|
them down all over the Web before getting started.</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>10.2 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>An engine-driven design. Key services are actually classes that can be
|
|
loaded at runtime, making it easy for users to add or subtract features.</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>. This also means no
|
|
Makefiles are needed.</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 much 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 (compared 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>
|
|
<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. Otherwise, the
|
|
program will keep chugging along, storing data, allowing you to fix the problem
|
|
at your leisure, without losing any data.</p>
|
|
<h2>10.3 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>
|
|
<tr>
|
|
<td>SQL type</td>
|
|
<td>A type that appears in the SQL database. This usually looks
|
|
something like '<span class="code">outTemp</span>', '<span class="code">barometer</span>',
|
|
'<span class="code">extraTemp1</span>', and so on.</td>
|
|
</tr>
|
|
<tr>
|
|
<td>observation type</td>
|
|
<td>A type that can be used in the presentations. This is generally all
|
|
of the SQL types, plus calculated data (such as <span class="code">rms</span>
|
|
or <span class="code">vecavg</span>).</td>
|
|
</tr>
|
|
</table>
|
|
<h2>10.4 Units</h2>
|
|
<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 U.S. Customary units internally. </li>
|
|
<li>In the database. The unit system of any individual record is indicated
|
|
by the "<span class="code">usUnits</span>" field. The numerical value 1
|
|
indicates U.S. Customary, 2 indicates Metric.
|
|
</li>
|
|
<li>In the presentation (i.e., html and image files). </li>
|
|
</ol>
|
|
<p>The general strategy is that measurements are stored internally in the native
|
|
measurement system of the weather instrument. That is, the units used in #1 and
|
|
#2 are always the same. With Version 1.5, weewx supports translations between #2
|
|
and #3, allowing any unit system to be used in the presentation layer.</p>
|
|
<p>It would be easy enough to support an instrument that uses metric units
|
|
internally, although this has not been done yet. </p>
|
|
<h2>10.5 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>10.6 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">weewx</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
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bulletproof against changes in DST algorithms, etc:</p>
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<p class="tty">time_dt = datetime.datetime.fromtimestamp(last_ts)</p>
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<p class="tty">delta = datetime.timedelta(seconds=10800)</p>
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<p class="tty">next_dt = time_dt + delta</p>
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<p class="tty">next_ts = int(time.mktime(next_dt.timetuple()))</p>
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<p>Other time conversion problems are handled in a similar manner.</p>
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</body>
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</html>
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