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<h1 class="title">User's Guide to the <span class="code">weewx</span> Weather System<br />
<span style="font-size:70%">
Version: 2.2
</span>
</h1>
<p>
This is the complete guide to installing and configuring <span class="code">weewx</span>.
</p>
<p>
Quick-start guides are available for
<ul>
<li><a href='linux.htm'>Installing on Linux</a> &mdash; Debian, Ubuntu, Mint, Redhat, CentOS, Fedora</li>
<li><a href='debian.htm'>Installing from DEB package</a> &mdash; Debian, Ubuntu, Mint</li>
<li><a href='redhat.htm'>Installing from RPM package</a> &mdash; Redhat, CentOS, Fedora</li>
</ul>
</p>
<p>
For information on customizing <span class="code">weewx</span>, see the <a href="customizing.htm">Customization Guide</a>.
</p>
<p>
For instructions on upgrading from previous versions, see the <a href="upgrading.htm">Upgrade Guide</a>.
</p>
<p>
For installation on the SheevaPlug, see <a href="sheeva.htm">Notes on porting to the SheevaPlug</a>.
</p>
<h1>Table of Contents</h1>
<div id="technical_content">
<div id="toc"></div>
<h1 id="About_weewx">About <span class="code">weewx</span></h1>
<p><span class="code">weewx</span> is a piece of software, written in
<a href="http://www.python.org">Python</a>, that interacts with your weather
station to produce plots, reports, and HTML pages. It can optionally upload
the reports to a remote Web server as well as publish to the
<a href="http://www.wunderground.com">WeatherUnderground</a> or
<a href="http://www.pwsweather.com/">PWSweather.com</a>. It uses modern software
concepts, making it simple, robust, and easy to extend. For an example station
see <a href="http://www.threefools.org/weewx">Hood River West</a>. </p>
<p>Key features: </p>
<ul>
<li>An easy to understand, simple, extensible micro-kernel architecture;</li>
<li>Uploads to popular weather sites, such as Weather Underground and CWOP;</li>
<li>Uploads to your website using FTP or rsync;</li>
<li>Support for multiple <em>skins</em>;</li>
<li>Simple, but extensible templating system;</li>
<li>Support for multiple unit systems;</li>
<li>Support for sqlite or MySQL databases;</li>
<li>Calibration corrections;</li>
<li>Ability to extend <span class="code">weewx</span> with new services
and reports. </li>
</ul>
<p>I wrote <span class="code">weewx</span> over the winter of 2008-2009 for
two reasons: it was a wet and miserable winter here in Oregon with not much
else to do, so there was no good reason not to, and because I wanted a simple,
easy-to-understand server to run my Davis VantagePro2 weather station on a Linux
box. I had been using <a href="http://www.wviewweather.com/">wview</a>, which
is a high-performance and feature rich system authored by Mark Teel with lots
of users. Written in C, it&#39;s an efficient system that can run on underpowered
boxes. In exchange, it&#39;s huge (45,000+ lines of code), tightly integrated
in with its companion library, radlib (another 14,000+ lines), and very complex,
making it difficult to understand and reliably customize. I wanted something
more modern and much, much simpler. </p>
<p>Having made a career in C++ and Java, I was also interested in some more
modern languages, so I thought I&#39;d try either Python or Ruby (although,
truth be told, the roots of Python are nearly as old as C++!). I ended up picking
Python because its libraries are more mature and there are many mores choices
for third party libraries. </p>
<p><span class="code">Weewx</span> weighs in at well under 6,000 lines of code,
with another 3,800 comment lines. Because it is pure Python, it requires no
makefiles, no builds, no special installs. It offers very powerful configuration
and templating options, as well as an internally extensible engine, making it
easy to customize. Its internal modular design and use of modern exception handling
make it very robust and difficult to crash. It is also architecturally very
simple and easy to understand.</p>
<h1>Supported hardware</h1>
<p>
Many types of station hardware are supported. In addition to hardware support, <span class="code">weewx</span> comes with a software simulator, useful for testing and evaluation.
</p>
<table style="width: 90%" class="center">
<tr>
<td><strong>Vendor</strong></td>
<td><strong>Model</strong></td>
<td><strong>Link</strong></td>
<td><strong>Required<br/>Package</strong></td>
<td><strong>Station<br/>Driver</strong></td>
<td><strong>Maturity</strong></td>
<td><strong>Notes</strong></td>
</tr>
<tr>
<td class="text_highlight" rowspan="3">Ambient Weather</td>
<td>WS1090</td>
<td>USB</td>
<td class="code">pyusb</td>
<td>FineOffsetUSB</td>
<td></td>
<td>&nbsp;</td>
</tr>
<tr>
<td>WS2080</td>
<td>USB</td>
<td class="code">pyusb</td>
<td>FineOffsetUSB</td>
<td>Tested</td>
<td>&nbsp;</td>
</tr>
<tr>
<td>WS2090</td>
<td>USB</td>
<td class="code">pyusb</td>
<td>FineOffsetUSB</td>
<td></td>
<td>&nbsp;</td>
</tr>
<tr>
<td class="text_highlight" rowspan="3">Davis<sup><a href='#vantage'>1</a></sup></td>
<td>VantagePro2</td>
<td>Serial or USB</td>
<td class="code">pyserial</td>
<td>Vantage</td>
<td>Tested</td>
<td></td>
</tr>
<tr>
<td>VantagePro2</td>
<td>WeatherLink IP</td>
<td class="code">&nbsp;</td>
<td>Vantage</td>
<td>Tested</td>
<td>&nbsp;</td>
</tr>
<tr>
<td>VantageVue</td>
<td>Serial or USB</td>
<td class="code">pyserial</td>
<td>Vantage</td>
<td>Tested</td>
<td>&nbsp;</td>
</tr>
<tr>
<td class="text_highlight" rowspan="2">Elecsa</td>
<td>6975</td>
<td>USB</td>
<td class="code">pyusb</td>
<td>FineOffsetUSB</td>
<td></td>
<td>&nbsp;</td>
</tr>
<tr>
<td>6976</td>
<td>USB</td>
<td class="code">pyusb</td>
<td>FineOffsetUSB</td>
<td></td>
<td>&nbsp;</td>
</tr>
<tr>
<td class="text_highlight" rowspan="11">Fine Offset<sup><a href='#fousb'>4</a></sup></td>
<td>WH1080</td>
<td>USB</td>
<td class="code">pyusb</td>
<td>FineOffsetUSB</td>
<td></td>
<td>&nbsp;</td>
</tr>
<tr>
<td>WH1081</td>
<td>USB</td>
<td class="code">pyusb</td>
<td>FineOffsetUSB</td>
<td></td>
<td>&nbsp;</td>
</tr>
<tr>
<td>WH1091</td>
<td>USB</td>
<td class="code">pyusb</td>
<td>FineOffsetUSB</td>
<td></td>
<td>&nbsp;</td>
</tr>
<tr>
<td>WH1090</td>
<td>USB</td>
<td class="code">pyusb</td>
<td>FineOffsetUSB</td>
<td></td>
<td>&nbsp;</td>
</tr>
<tr>
<td>WS1080</td>
<td>USB</td>
<td class="code">pyusb</td>
<td>FineOffsetUSB</td>
<td></td>
<td>&nbsp;</td>
</tr>
<tr>
<td>WA2080</td>
<td>USB</td>
<td class="code">pyusb</td>
<td>FineOffsetUSB</td>
<td></td>
<td>&nbsp;</td>
</tr>
<tr>
<td>WA2081</td>
<td>USB</td>
<td class="code">pyusb</td>
<td>FineOffsetUSB</td>
<td></td>
<td>&nbsp;</td>
</tr>
<tr>
<td>WH2080</td>
<td>USB</td>
<td class="code">pyusb</td>
<td>FineOffsetUSB</td>
<td></td>
<td>&nbsp;</td>
</tr>
<tr>
<td>WH2081</td>
<td>USB</td>
<td class="code">pyusb</td>
<td>FineOffsetUSB</td>
<td></td>
<td>&nbsp;</td>
</tr>
<tr>
<td>WH3080</td>
<td>USB</td>
<td class="code">pyusb</td>
<td>FineOffsetUSB</td>
<td></td>
<td>&nbsp;</td>
</tr>
<tr>
<td>WH3081</td>
<td>USB</td>
<td class="code">pyusb</td>
<td>FineOffsetUSB</td>
<td></td>
<td>&nbsp;</td>
</tr>
<tr>
<td class="text_highlight">National Geographic</td>
<td>265</td>
<td>USB</td>
<td class="code">pyusb</td>
<td>FineOffsetUSB</td>
<td></td>
<td>&nbsp;</td>
</tr>
<tr>
<td class="text_highlight" rowspan="3">Oregon Scientific<sup><a href='#wmrusb'>2</a>, <a href='#wmr9xx'>3</a></sup></td>
<td>WMR100N</td>
<td>USB</td>
<td class="code">pyusb</td>
<td>WMR-USB</td>
<td>Tested</td>
<td>&nbsp;</td>
</tr>
<tr>
<td>WMR918</td>
<td>Serial</td>
<td class="code">pyserial</td>
<td>WMR-918</td>
<td></td>
<td>&nbsp;</td>
</tr>
<tr>
<td>WMR968</td>
<td>Serial</td>
<td class="code">pyserial</td>
<td>WMR-918</td>
<td>Tested</td>
<td>&nbsp;</td>
</tr>
<tr>
<td class="text_highlight">Tycon</td>
<td>TP1080WC</td>
<td>USB</td>
<td class="code">pyusb</td>
<td>FineOffsetUSB</td>
<td></td>
<td>&nbsp;</td>
</tr>
<tr>
<td class="text_highlight" rowspan="2">Watson</td>
<td>W-8681</td>
<td>USB</td>
<td class="code">pyusb</td>
<td>FineOffsetUSB</td>
<td></td>
<td>&nbsp;</td>
</tr>
<tr>
<td>WX-2008</td>
<td>USB</td>
<td class="code">pyusb</td>
<td>FineOffsetUSB</td>
<td></td>
<td>&nbsp;</td>
</tr>
</table>
<ol>
<li><a name='vantage'>Davis &quot;Vantage&quot;</a> series of weather stations, including the
<a href="http://www.davisnet.com/weather/products/vantage-pro-professional-weather-stations.asp">
VantagePro2</a>&trade; and <a href="http://www.vantagevue.com/">VantageVue</a>&trade;,
using serial, USB, or
<a href="http://www.davisnet.com/weather/products/weather_product.asp?pnum=06555">
WeatherLinkIP</a>&trade; connections. Both the &quot;Rev A&quot; (firmware
dated before 22 April 2002) and &quot;Rev B&quot; versions are supported.
</li>
<li><a name='wmrusb'>Oregon Scientific WMR-USB</a> series. Tested on the
<a href="http://us.oregonscientific.com/cat-Weather-sub-Professional-Weather-Stations-prod-Pro-Wireless-Weather-Station.html">WMR100N</a>, other stations may work as well.</li>
<li><a name='wmr9xx'>Oregon Scientific WMR-918/968</a> series. Tested on the
<a href="http://www.oregonscientificstore.com/oregon_scientific/product.asp?itmky=659831">Oregon Scientific WMR-968</a>, other stations may work as well.</li>
<li><a name='fousb'>Fine Offset</a> series of weather stations. These are branded by
many vendors, including Ambient Weather, National Geographic, Watson,
Elecsa, Tycon, Maplin, Froggit, and others. Tested on the
<a href="http://www.ambientweather.com/amws2080.html">Ambient Weather WS2080</a>, other stations may work as well.</li>
</ol>
<h1>Installing <span class="code">weewx</span></h1>
<p>
<span class='code'>weewx</span> can be installed from source using
<span class='code'>setup.py</span> or from a DEB or RPM package.
Installation from source is the recommended method for those who
plan to make modifications and hack the <span class='code'>weewx</span>.
The package approach is somewhat simpler, but requires root privileges.
</p>
<h2><a href='linux.htm'>Installing on Linux</a></h2>
<p>Including Debian, Ubuntu, Mint, Redhat, CentOS, Fedora</p>
<h2><a href='debian.htm'>Installing from DEB package</a></h2>
<p>Including Debian, Ubuntu, Mint</p>
<h2><a href='redhat.htm'>Installing from RPM package</a></h2>
<p>Including Redhat, CentOS, Fedora</p>
<h2><a href='installing.htm'>Installing from Scratch</a></h2>
<p>Because it is Pure Python, <span class='code'>weewx</span> <i>should</i>
install and run on any platform with Python.</p>
<h1>Configuring <span class="code">weewx</span></h1>
<p>This section covers configuring <span class="code">weewx</span>, in particular
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>$WEEWX_ROOT</em></span> refers to
the <span class="code">weewx</span> root directory, generally
<span class="code">/home/weewx</span>. The subdirectories <span class="code">
archive</span>, <span class="code">skins</span>, and <span class="code">public_html</span>
are expected to be found there. </p>
<h2 id="Configuring_your_Davis_console">Configuring the Davis Vantage console</h2>
<p>Weewx comes with a configuration utlity, <span class="code">config_vp.py</span>,
that can set many of the on-board EEPROM constants in the Davis Vantage stations,
such as its archive interval, altitude, rain bucket type, <em>etc.</em> </p>
<p>Run it with the configuration file as an argument and <span class="code">
--help</span> as an option to see its usage: </p>
<pre class="tty"><em>$WEEWX_ROOT</em>/bin/config_vp.py <em>$WEEWX_ROOT</em>/weewx.conf --help </pre>
<p>This will print out something like:</p>
<pre class="tty"
>Usage: config_vp.py: config_path [--help] [--info] [--clear] [--set-interval=SECONDS] [--set-altitude=FEET]
[--set-barometer=inHg] [--set-bucket=CODE] [--set-rain-year-start=MM] [--set-time]
[--start | -- stop]
Configures the VantagePro weather station.
Options:
-h, --help show this help message and exit
--info To print configuration, reception, and barometer
calibration information about your weather station.
--clear To clear the memory of your weather station.
--set-interval=SECONDS Sets the archive interval to the specified number of
seconds. Valid values are 60, 300, 600, 900, 1800,
3600, or 7200.
--set-altitude=FEET Sets the altitude of the station to the specified
number of feet.
--set-barometer=inHg Sets the barometer reading of the station to a known
correct value in inches of mercury. Specify 0 (zero)
to have the console pick a sensible value.
--set-bucket=CODE Set the type of rain bucket. Specify '0' for 0.01
inches; '1' for 0.2 MM; '2' for 0.1 MM
--set-rain-year-start=MM Set the rain year start (1=Jan, 2=Feb, etc.).
--set-time Set the onboard clock to the current time.
--start Start the logger.
--stop Stop the logger.
Mutating actions will request confirmation before proceeding.</pre>
<p>It is useful to run it with the <span class="code">--info</span> option to
see what the current EEPROM settings are on your station: </p>
<pre class="tty"><em>$WEEWX_ROOT</em>/bin/config_vp.py <em>$WEEWX_ROOT</em>/weewx.conf --info </pre>
<p>This will print out something like: </p>
<pre class="tty">
VantagePro EEPROM settings:
CONSOLE TYPE: VantagePro2
CONSOLE FIRMWARE:
Date: Nov 28 2005
Version: &lt;Unavailable&gt;
CONSOLE SETTINGS:
<span class="highlight">Archive interval: 300 (seconds)</span>
<span class="highlight">Altitude: 700 (foot)</span>
Wind cup type: large
<span class="highlight">Rain bucket type: 0.01 inches</span>
<span class="highlight">Rain year start: 10</span>
<span class="highlight">Onboard time: 2012-09-30 16:48:27 PDT (1349048907)</span>
CONSOLE DISPLAY UNITS:
Barometer: mbar
Temperature: degree_F
Rain: inch
Wind: knot
CONSOLE STATION INFO:
Latitude (onboard): 45.7
Longitude (onboard): -121.6
Time zone code: 4
Use manual or auto DST? AUTO
DST setting: N/A
GMT offset: -8.0 hours
Use GMT offset or time zone? TIME_ZONE
RECEPTION STATS:
Total packets received: 22843
Total packets missed: 748
Number of resynchronizations: 0
Longest good stretch: 534
Number of CRC errors: 647
BAROMETER CALIBRATION DATA:
<span class="highlight">Current barometer reading: 30.209 inHg</span>
Altitude: 700 feet
Dew point: 48 F
Virtual temperature: 66 F
Humidity correction factor: 23
Correction ratio: 1.025
Correction constant: +0.027 inHg
Gain: -1.000
Offset: -1.000</pre>
<p>Note that console version number is only available on consoles with firmware
dates after about 2006.</p>
<p><span class="highlight">Highlighted</span> values can be changed.</p>
<p>For example, to change the archive interval to 10 minutes (600 seconds):</p>
<pre class="tty"><em>$WEEWX_ROOT</em>/bin/config_vp.py $WEEWX_ROOT/weewx.conf --set-interval=600</pre>
<p>Other parameters can be set in a similar manner.</p>
<h3 id="Archive_interval">Archive interval</h3>
<p>Valid archive intervals are 60, 300, 600, 900, 1800, 3600, and 7200. However,
if you are ftp&#39;ing lots of files to a server, setting it to 60 seconds may
not give enough time to have them all uploaded before the next archive record
is due. If this is the case, you should pick an archive interval of at least
300 seconds, or trim the number of files you are using. </p>
<p>I have found that a five minute (300 seconds) archive interval works well
for the VantagePro2. Because of the large amount of onboard memory it carries,
going to a larger interval really does not have any advantages. </p>
<p><em>Choose your archiving interval carefully! </em>Once chosen, it cannot
be changed without messing up your statistics (highs and lows will be OK, but
averages and rms wind speed will be wrong). </p>
<h3>Rain bucket type</h3>
<p>Normally, this is set by Davis, but if you have replaced your bucket with
a different kind, you might want to reconfigure. For example, to change to a
0.1MM bucket (bucket code &quot;2&quot;), use the following:</p>
<p class="tty"><em>$WEEWX_ROOT</em>/bin/config_vp.py $WEEWX_ROOT/weewx.conf
--set-bucket=2</p>
<h2>Configuring MySQL</h2>
<p>This section applies only for those using MySQL.</p>
<p>Assuming that you want to use the default database configuration, your
<span class="code"><a href="#[Databases]">[Databases]</a></span> section
should
look something like this:</p>
<pre class="tty">
[Databases]
[[archive_mysql]]
host = localhost
user = weewx
password = weewx
database = weewx
driver = weedb.mysql
[[stats_mysql]]
host = localhost
user = weewx
password = weewx
database = stats
driver = weedb.mysql</pre>
<p>This assumes user '<span class="code">weewx</span>' would have password '<span class="code">weewx</span>'.
Adjust as necessary.</p>
<p>If you wish, databases '<span class="code">weewx</span>' and '<span class="code">stats</span>'
can be combined into one database, although this will make it harder to drop
the latter should you need to rebuild the stats database at a later time.</p>
<p>You will need to give the necessary permissions for databases '<span class="code">weewx</span>'
and '<span class="code">stats</span>' to whatever MySQL user you choose, by
default, user '<span class="code">weewx</span>'. Here are the necessary minimum
permissions:</p>
<pre class="tty">
mysql&gt; CREATE USER 'weewx'@'localhost' IDENTIFIED BY 'weewx';
mysql&gt; GRANT select, update, create, delete, insert ON weewx.* TO weewx@localhost;
mysql&gt; GRANT select, update, create, delete, insert ON stats.* TO weewx@localhost;</pre>
<h2>Editing the configuration file <span class="code">weewx.conf</span></h2>
<p>Station specific information is set in the configuration file <em>
<span class="code">$WEEWX_ROOT/weewx.conf</span></em>. (There is another configuration
file <span class="code">skin.conf</span> for presentation-specific options,
which is described in the <a href="customizing.htm">Customizing Guide</a> under section <em>
<a href="customizing.htm#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 <span class="config_important"><strong>highlighted</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 &quot;default
value&quot; 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 &quot;default value&quot;. </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.</p>
<p class="config_option">debug </p>
<p>Set to 1 to have the program perform extra debug checks, as well as emit
extra information in the log file. Otherwise, set to 0. Default is 0 (no debug).
</p>
<p class="config_important">WEEWX_ROOT </p>
<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>.
The <span class="code">weewx</span> data subdirectories <span class="code">skins</span>,
<span class="code">archive</span>, and <span class="code">public_html</span>
are expected to be found here. 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> during
installation. Required. No default.
</p>
<p class="config_option">socket_timeout </p>
<p>Set to how long to wait before declaring a socket time out. This is used
when FTP&#39;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 your weather station setup. </p>
<p class="config_important">location </p>
<p>The station location should be a UTF-8 string that describes the
geography of where your weather station is located, such as
<span class="code">Hood River, Oregon</span>. Required.
No default. </p>
<p class="config_important">latitude <br />
longitude </p>
<p>The lat/lon should be set in decimal degrees, negative for southern and western
hemispheres, respectively. Required. No default. </p>
<p class="config_option"><span class="config_important">altitude</span></p>
<p>Normally the station altitude is downloaded from your hardware, but not all
stations support this. Set to the altitude of the station and the unit used
for the altitude. Example: </p>
<pre class="tty">altitude = 700, foot</pre>
<p class="config_option"><span class="config_important">rain_year_start
</span></p>
<p>Normally the start of the rain year is downloaded from your hardware, but
not all stations support this. Set to the start of your rain year, for example,
10, if your rain year starts in October (as mine does). Default is 1. </p>
<p class="config_option">week_start </p>
<p>Start of the week. 0=Monday, 1= Tuesday, ... , 6 = Sunday. Default is 6 (Sunday)
</p>
<p class="config_important">station_type </p>
<p>Set to the type of hardware you are using. Valid options include:</p>
<table style="width: 60%" class="center">
<tr>
<td class="code">Vantage</td>
<td style="height: 33px">Davis Vantage weather stations</td>
</tr>
<tr>
<td class="code">WMR-USB</td>
<td>Oregon Scientific WMR-USB series stations</td>
</tr>
<tr>
<td class="code">WMR-918</td>
<td>Oregon Scientific WMR-918/968 series station</td>
</tr>
<tr>
<td class="code">FineOffsetUSB</td>
<td>Fine Offset USB stations</td>
</tr>
</table>
<h3 class="config_section">[Vantage]</h3>
<p>This section is for options relating to the Davis Vantage series of hardware
(<em>VantagePro, VantagePro2</em> or <em>VantageVue</em>).</p>
<p class="config_important">type </p>
<p>Set to either <span class="code">serial</span>, for a serial or USB
connection to the VantagePro (by far the most common), or to
<span class="code">ethernet</span> for the WeatherLinkIP. No default.</p>
<p class="config_important">port </p>
<p>If you chose <span class="code">serial</span>, for <span class='code'>type</span>,
then set to the serial port name used by the station. For example,
<span class="code">/dev/ttyUSB0</span> is a common location for USB
ports, <span class="code">/dev/ttyS0</span> for serial ports. Otherwise,
not required. No default. </p>
<p class="config_important">host </p>
<p>If you chose <span class="code">ethernet</span>, then specify either
the IP address (<em>e.g.</em>, <span class="code">192.168.0.1</span>)
or hostname (<em>e.g.</em>, <span class="code">console.mydomain.com</span>)
to the console. Otherwise, not required. No default. </p>
<p class="config_option">baudrate </p>
<p>Set to the baudrate of the station. The default is 19200. </p>
<p class="config_option">tcp_port </p>
<p>The port where WeatherLinkIP will be listening. Default is 22222.
</p>
<p class="config_option">tcp_send_delay </p>
<p>How long to block after sending a socket packet to the WeatherLinkIP.
Default is 1 second. </p>
<p class="config_option">iss_id </p>
<p>Set to the ID number of the Integrated Sensor Suite (ISS). This is used
in the formula to calculate reception quality for wireless stations.
Default is 1. </p>
<p class="config_option">timeout </p>
<p>How many seconds to wait for a response from the station before giving
up. Default is 5 seconds. </p>
<p class="config_option">wait_before_retry </p>
<p>How many seconds to wait before retrying. 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>
<p class="config_option">max_tries </p>
<p>How many times to try again before giving up. Default is 4. </p>
<h3 class="config_section">[WMR-USB]</h3>
<p>This section is for options relating to the Oregon Scientific WMR series
of weather stations with USB connectors.</p>
<p class="config_option">stale_wind</p>
<p>How long a wind record can be used to calculate wind chill (in seconds).
Default is 30.</p>
<h3 class="config_section">[WMR-918]</h3>
<p>This section is for options relating to the Oregon Scientific WMR-918
series of weather stations with serial connectors.</p>
<p class="config_important">type</p>
<p>For the moment, only <span class="code">serial</span> is supported.</p>
<p class="config_important">port </p>
<p>Along with the <span class="code">serial</span> option above, you
must set the serial port name used by the station. For example,
<span class="code">/dev/ttyUSB0</span> is a common location for USB
ports, <span class="code">/dev/ttyS0</span> for serial ports.
No default. </p>
<p class="config_option">stale_wind</p>
<p>How long a wind record can be used to calculate wind chill (in seconds).
Default is 30.</p>
<h3 class="config_section">[FineOffsetUSB]</h3>
<p>This section is for options relating to the Fine Offset series of
weather stations with USB connectors.</p>
<p class="config_important">model</p>
<p>Set to the station model. For example, WH1080, WS2080, WH3081, etc. </p>
<h3 class="config_section">[Simulator]</h3>
<p>This section is for options relating to the software weather station simulator
that comes with <span class="code">weewx</span>.</p>
<p class="config_option">loop_interval</p>
<p>The time (in seconds) between emitting loop packets. Default is 2.5</p>
<p class="config_option">mode</p>
<p>One of either <span class='code'>simulator</span> or <span class='code'>generator</span></p>
<table class="indent" style="width: 80%">
<tr>
<td class="code">simulator</td>
<td>Real-time simulator. It will sleep between emitting packets [Default]</td>
</tr>
<tr>
<td class="code">generator</td>
<td>Emit packets as fast as it can. Useful for testing.</td>
</tr>
</table>
<p class="config_option">start</p>
<p>The start time for the generator in the format <span class="code">YYYY-MM-DD
hh:mm</span>. Optional. Default is the present time.</p>
<h3 class="config_section">[StdRESTful]</h3>
<p>This section is for configuring the <span class="code">StdRESTful</span>
service, which uploads to simple
<a href="http://en.wikipedia.org/wiki/Representational_State_Transfer">RESTful</a>
servers such as the <a href="http://www.wunderground.com/">Weather Underground</a>,
<a href="http://www.pwsweather.com/">PWSweather.com</a>, or
<a href="http://www.wxqa.com/">CWOP</a>. </p>
<h4 class="config_section">[[Wunderground]]</h4>
<p><span class="code">Weewx </span>can send your current data to the
<a href="http://www.wunderground.com/">Weather Underground</a>. If you do not
wish to do this, comment out the two options below. </p>
<p class="config_important">station </p>
<p>Set to your Weather Underground station ID (<em>e.g.</em>, <span class="code">KORHOODR3</span>).
Required. </p>
<p class="config_important">password </p>
<p>Set to your Weather Underground password. Required. </p>
<h4 class="config_section">[[PWSweather]]</h4>
<p><span class="code">Weewx </span>can send your current data to the
<a href="http://www.pwsweather.com/">PWSweather.com</a> service. If you do not
wish to do this, comment out the two options below. </p>
<p class="config_important">station </p>
<p>Set to your PWSweather station ID. Required. </p>
<p class="config_important">password </p>
<p>Set to your PWSweather password. Required. </p>
<h4 class="config_section">[[CWOP]]</h4>
<p><span class="code">Weewx</span> can send your data to the
<a href="http://www.wxqa.com/">Citizen Weather Observer Program</a>. If you
do not wish to do this, comment out option <span class="code">station</span>
below. </p>
<p class="config_important">station </p>
<p>Set to your CWOP station ID (<em>e.g.</em>, <span class="code">CW1234</span>). Required.
</p>
<p class="config_important">passcode </p>
<p>This is used for APRS (amateur radio) stations only. Set to the passcode
given to you by the CWOP operators. Otherwise, leave this option commented out
[Required for APRS stations; ignored for others] </p>
<p class="config_option">server </p>
<p>A comma separated list of servers:ports to try. Unless you have a good reason
to change this, use the servers listed. [Required.] </p>
<p class="config_option">interval </p>
<p>The interval in seconds between posts. Because CWOP is heavily used, the
operators discourage very frequent posts. Every 5 minutes (300 seconds) is fine,
but they prefer every 10 minutes (600 s) or even longer. Setting this value
to zero will cause every archive record to be posted. [Optional. Default is
zero.] </p>
<p class="config_option">stale </p>
<p>How old a record can be before it will not be used for a catch up. CWOP does
not use the timestamp on a posted record. Instead, they use the wall clock time
that it came in. This means that if your station is off the air for a long period
of time, then <span class="code">weewx</span> attempts a catch up, old data
could be interpreted as the current conditions. [Optional. Default is 1800 seconds.]
</p>
<h3 id="[Reports]" class="config_section">[StdReport]</h3>
<p>This section is for configuring the <span class="code">StdReport</span> service,
which 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, normally the 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
<a href="customizing.htm">Customizing Guide</a>.
</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 &quot;<span class="code">Standard</span>&quot;, which generates
four HTML pages (&quot;day&quot;, &quot;week&quot;, &quot;month&quot;, and &quot;year&quot;
observations), plot graphs for same, an RSS feed, 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 &quot;report&quot; doesn&#39;t actually generate anything, it
uses the report machinery to upload files from directory <span class="code">
<em>$HTML_ROOT</em></span> to a remote webserver. It does an incremental update,
that is, it only FTPs any files that have changed, saving the outgoing bandwidth
of your Internet connection. </p>
<p>If you do not use such a server, comment out the first four options below.
</p>
<p class="config_important">user </p>
<p>Set to the username you use for your FTP connection to your web server. Required.
No default. </p>
<p class="config_important">password </p>
<p>Set to the password you use for your FTP connection to your web server. Required.
No default. </p>
<p class="config_important">server </p>
<p>Set to the name of your web server (<em>e.g.</em>,
<a href="http://www.threefools.org">www.threefools.org</a>, in my case). Required.
No default </p>
<p class="config_important">path </p>
<p>Set to the path where the weather data will be stored on your webserver (<em>e.g.</em>, <span class="code">/weather</span>).
NB: some FTP servers require a leading slash (&#39;<span class="code">/</span>&#39;),
some don&#39;t. Required. No default. </p>
<p class="config_important">passive </p>
<p>Set to 1 if you wish to use the more modern, FTP passive mode, 0 if you wish
to use active mode. Passive mode generally works better through firewalls, but
not all FTP servers do a good job of supporting it. See
<a href="http://slacksite.com/other/ftp.html">Active FTP vs. Passive FTP, a
Definitive Explanation</a> for a good explanation of the difference. Default
is 1 (passive mode). </p>
<p class="config_option">max_tries </p>
<p><span class="code">Weewx</span> will try up to this many times to FTP a file
up to your server before giving up. Default is 3. </p>
<h4 class="config_section">[[RSYNC]]</h4>
<p>While this &quot;report&quot; doesn&#39;t actually generate anything, it
uses the report machinery to upload files from directory <span class="code">
<em>$HTML_ROOT</em></span> to a remote webserver. It does an incremental update,
that is, it only synchronizes those 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 options below. </p>
<p class="config_important">server </p>
<p>Set to the name of your web server (<em>e.g.</em>,
<a href="http://www.threefools.org">www.threefools.org</a>, in my case). Required.
No default </p>
<p class="config_important">user </p>
<p>Set to the ssh username you use for your rsync connection to your web server.
The local user that weewx runs as must have passwordless ssh configured for
user@server. 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 (<em>e.g.</em>, <span class="code">/weather</span>).
Required. No default. </p>
<p class="config_important">delete </p>
<p>Files that don't exist in the local report are removed from the remote location.
<em>USE WITH CAUTION:</em> If you make a mistake in setting the
<span class="code">path</span>, this can cause unexpected files to be deleted
on the remote server. Valid values are 1 to enable and 0 to disable. Required.
Default is 0.</p>
<h3 id="[StdConvert]" class="config_section">[StdConvert]</h3>
<p>This section is for configuring the <span class="code">StdConvert</span>
service. This service acts as a filter, converting the unit system coming off
your hardware to a target output unit system. Everything that follows, including
the archiving service, will use the target unit system. Hence, your data
will be stored using your chosen unit system. </p>
<p><em>Once chosen, it cannot be changed!</em> Weewx does not allow you to mix
unit systems within the databases. You must chose one or the other and then
stick with it. This means that users coming from wview (which uses US Customary)
should not change the default setting. Having said this, there is a way of reconfiguring
the database to use another unit system. See the section
<a href="customizing.htm#Changing_the_unit_system">Changing the Unit System</a>
in the Customizing Guide.</p>
<p>Note that whatever you choose here, it does not affect your options for the
unit system to be used for <i>reporting</i>. Because of this, unless you
have a special purpose application, there is really no good reason to change
from the default, which is <span class="code">US</span>. However, if you do
decide to change to Metric, be sure to read the sections <span class="code">
<a href="#Calibrate">[StdCalibrate]</a></span> and <span class="code">
<a href="#QC">[StdQC]</a></span> below, and change the units there as well.</p>
<p class="config_option">target_unit</p>
<p>Set to either <span class="code">US</span> or <span class="code">METRIC</span>.
Default is <span class="code">US</span>.</p>
<h3 id="Calibrate" class="config_section">[StdCalibrate]</h3>
<p>This section is for configuring the <span class="code">StdCalibrate</span>
service. This service offers an opportunity to correct for any calibration errors
in your instruments. It is very general and flexible. </p>
<p>Because this service is normally run after <span class="code">StdConvert</span>,
the units to be used should be the same as the target unit system chosen in
<a href="#[StdConvert]"><span class="code">StdConvert</span></a> above. It is
also important that this service be run before the archiving service
<span class="code">StdArchive</span>, so that it is the corrected data that
is stored. </p>
<p>If you do not wish to apply any calibrations, you can leave it out of
<span class="code"><a href="#service_list">service_list</a></span>, the list
of services to be run, and it will not be loaded or run at all. </p>
<h4 class="config_section">[[Corrections]]</h4>
<p>In this section you list all <em>correction expressions</em>. For example,
say that you know your outside thermometer reads high by 0.2°F. You could add
the expression: </p>
<pre>outTemp = outTemp - 0.2</pre>
<p>Perhaps you need a linear correction around a reference temperature of 68°F:
</p>
<pre>outTemp = outTemp + (outTemp-68) * 0.02</pre>
<p>It is even possible to do corrections involving more than one variable. Suppose
you have a temperature sensitive barometer: </p>
<pre>barometer = barometer + (outTemp-32) * 0.0091</pre>
<p>All correction expressions are run in the order given. </p>
<p>Both LOOP data and archive data will be corrected. </p>
<p>If you are using a Davis Vantage instrument and all you require is a simple
correction offset, this can also be done in the hardware. See your manual for
instructions. </p>
<h3 id="QC" class="config_section">[StdQC]</h3>
<p>This section is for configuring the <span class="code">StdQC</span> service.
This service offers a very simple <em>Quality Control</em> that only checks
that values are within a minimum and maximum range.</p>
<p>Because this service is normally run after <span class="code">StdConvert</span>,
the units to be used should be the same as the target unit system chosen in
<a href="#[StdConvert]"><span class="code">StdConvert</span></a>. It is also
important that it be run after the calibration service, <span class="code">StdCalibrate
</span>and before the archiving service <span class="code">StdArchive</span>,
so that it is the calibrated and corrected data that is stored. </p>
<p>If you do not wish to use this service, you can leave it out of
<span class="code"><a href="#service_list">service_list</a></span>, the list
of services to be run, and it will not be loaded or run. </p>
<h4 class="config_section">[[MinMax]]</h4>
<p>In this section you list the observation types you wish to have checked,
along with their minimum and maximum values. The units should be in <em>the
same unit system as specified in section <span class="code">
<a href="#[StdConvert]">StdConvert</a></span> above</em>. </p>
<p>Example, </p>
<p class="tty">[[MinMax]] <br />
&nbsp; outTemp = -40, 120 <br />
&nbsp; barometer = 28, 32.5 <br />
&nbsp; outHumidity = 0, 100 </p>
<p>In this example, if a temperature should fall outside of the inclusive range
-40 °F through 120 °F, then it will be set to the null value,
<span class="code">None</span>, and ignored. In a similar manner, the acceptable
values for barometric pressure would be 28 through 32.5 inHg, for humidity 0
through 100%. </p>
<p>Both LOOP and archive data will be checked. </p>
<p>Knowing the details of how your hardware encodes data helps to minimize the
number of observations that need to be checked. For example, the VP2 devotes
only one unsigned byte to storing wind speed, and even then
<span class="code">0xff</span> is devoted to a bad value, so the only possible
values that could appear are 0 through 126 mph, a reasonable range. So, for
the VP2, there is no real point in checking wind speed. </p>
<h3 id="[StdArchive]" class="config_section">[StdArchive]</h3>
<p>This section is for configuring <span class="code">StdArchive</span>, the
service that stores data in the databases. Options allow choosing which database
to use for archiving and statistics.</p>
<p class="config_option">archive_database</p>
<p>The database to be used to store the archive data. This should match a section
given in the section <span class="code"><a href="#[Databases]">[Databases]</a></span>
below. Normally, this is set to <span class="code">archive_sqlite</span>. If
you are using MySQL, you will want to change this to <span class="code">
archive_mysql</span>.</p>
<p class="config_option">stats_database</p>
<p>The database to be used to store the statistical data. This should match
a section given in the section <span class="code"><a href="#[Databases]">[Databases]</a></span>
below. Normally, this is set to <span class="code">stats_sqlite</span>. If
you are using MySQL, you will want to change this to <span class="code">
stats_mysql</span>.</p>
<p class="config_option">archive_delay </p>
<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>
<p id="record_generation" class="config_option">record_generation</p>
<p>Set to whether records should be downloaded off the hardware (recommended),
or generated in software. If set to '<span class="code">hardware</span>', then
<span class="code">weewx</span> tries to download archive records from your
station. However, not all types of stations support this, in which case
<span class="code">weewx</span> falls back to software generation. A setting
of '<span class="code">hardware</span>' will work for most users. A notable
exception is <a href="http://www.wxforum.net/index.php?topic=10315.0">users
who have cobbled together homebrew serial interfaces</a> for the Vantage stations
that do not include memory for a logger. These users should set this option
to '<span class="code">software</span>', forcing software record generation.
Default is <span class="code">hardware</span>.</p>
<p class="config_option">archive_schema</p>
<p>This is used only when the archive database is first created. Thereafter,
it is downloaded from the database. It should point to a Python list
containing the archive database schema. The default is <span class="code">
user.schemas.defaultArchiveSchema</span>.</p>
<p class="config_option">stats_schema</p>
<p>This is used only when the stats database is first created. Thereafter,
it is downloaded from the database. It should point to a Python list
containing the stats database schema. The default is <span class="code">
user.schemas.defaultStatsSchema</span>.</p>
<h3 class="config_section">[StdTimeSynch]</h3>
<p>This section is for configuring <span class="code">StdTymeSynch</span>, a
service that can synchronize the onboard clock of station with your computer.
Not all weather station hardware supports this.</p>
<p class="config_option">clock_check</p>
<p>How often to check the clock on the weather station in seconds. Default is
14,400 seconds (every 4 hours)</p>
<p class="config_option">max_drift</p>
<p>The maximum amount of clock drift to tolerate, in seconds, before resetting
the clock. Default is 5.</p>
<h3 id="[Databases]" class="config_section">[Databases]</h3>
<p>This section lists actual database bindings. The name of each database is
given in double brackets below (for example, <span class="code">[[archive_sqlite]]</span>).
The details of the binding follow. You are free to add new bindings.</p>
<p>Note that if you choose the <a href="http://www.mysql.com/">MySQL</a> database
it is assumed that you know how to administer it. In particular, you will have
to set up a user with appropriate privileges to create and update the named
databases.</p>
<h4 class="config_section">[[archive_sqlite]]</h4>
<p>This definition uses the <a href="http://sqlite.org/">sqlite</a> database
engine to store archive data. It is open-source, simple, lightweight, highly
portable, and memory efficient. For most purposes it serves nicely.</p>
<p class="config_option">database</p>
<p>The path, relative to <span class="code">WEEWX_ROOT</span>, to the archive
sqlite file. Required.</p>
<h4 class="config_section">[[stats_sqlite]]</h4>
<p>This definition uses the <a href="http://sqlite.org/">sqlite</a> database
engine to store the statistical data. It is open-source, simple, lightweight,
highly portable, and memory efficient. For most purposes it serves nicely.</p>
<p class="config_option">database</p>
<p>The path, relative to <span class="code">WEEWX_ROOT</span>, to the stats
sqlite file. Required.</p>
<h4 class="config_section">[[archive_mysql]]</h4>
<p>This definition uses the MySQL database engine to store archive data. It
is free, highly-scalable, but more complicated to administer. </p>
<p class="config_option">host</p>
<p>The host the archive database is located on. Default is <span class="code">localhost</span>.</p>
<p class="config_option">user</p>
<p>The user name to be used to log into the server. Required.</p>
<p class="config_option">password</p>
<p>The password. Required.</p>
<p class="config_option">database</p>
<p>The name of the archive database inside the server. Required.</p>
<h4 class="config_section">[[stats_mysql]]</h4>
<p>This uses the MySQL database engine to store archive data. It is free, highly-scalable,
but more complicated to administer. </p>
<p>The host the stats database is located on. Default is <span class="code">localhost</span>.</p>
<p class="config_option">user</p>
<p>The user name to be used to log into the server. Required.</p>
<p class="config_option">password</p>
<p>The password. Required.</p>
<p class="config_option">database</p>
<p>The name of the statistical database inside the server. Required.</p>
<h3 class="config_section">[Engines]</h3>
<p>This section is used to configure the internal service engine in
<span class="code">weewx</span>. It is for advanced customization. Details on
how to do this can be found in the section <em>
<a href="customizing.htm#Customizing_the_weewx_service_engine">Customizing the
weewx service engine</a></em> of the <a href="customizing.htm">Customizing Guide</a>. </p>
<h4 class="config_section">[[WxEngine]]</h4>
<p>This section is for options used by the service engine. </p>
<p id="service_list" class="config_option">service_list </p>
<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. The standard list of services run by weewx is:
</p>
<pre>
service_list = weewx.wxengine.StdConvert, weewx.wxengine.StdCalibrate, weewx.wxengine, StdQC, \
weewx.wxengine.StdArchive, weewx.wxengine.StdTimeSynch, weewx.wxengine.StdPrint, \
weewx.wxengine.StdRESTful, weewx.wxengine.StdReport</pre>
<p>Note that this must all be on one line! </p>
<p>You can leave some of these services out if you do not need them. For example,
the bare minimum if you are using a Davis Vantage instrument, storing your data
in US Customary units, doing no data corrections or quality control and running
as a daemon (no printing to console) would be:</p>
<p class="tty">service_list = weewx.wxengine.StdArchive, weewx.wxengine.StdTimeSynch,
weewx.wxengine.StdRESTful, weewx.wxengine.StdReport</p>
<p>However, this will only make a slight difference in execution speed. </p>
<h1 id="Running_weewx">Running <span class="code">weewx</span></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&#39;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>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 data stored in your weather station into
the archive database. As the Davis VantagePro can store a couple thousand archive
records internally, this could take a minute or two. I&#39;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&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; # Note the PID of the weewxd.py process<br/>
kill -HUP <em>pid</em> # Send it a HUP signal<br/>
</p>
<p>Note that this <em>only</em> rereads the configuration file. It will not
reflect any changes you might have made to the code.</p>
<h2 id="Running_as_a_daemon">Running as a daemon</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>$WEEWX_ROOT</em>/util/init.d</span>. </p>
<table class="center" style="width: 90%">
<tr>
<td style="width: 25%">SuSE:</td>
<td class='tty'><em>$WEEWX_ROOT</em>/util/init.d/weewx.suse</td>
</tr>
<tr>
<td >Debian/Ubuntu/Mint:</td>
<td class='tty'><em>$WEEWX_ROOT</em>/util/init.d/weewx.debian</td>
</tr>
<tr>
<td >Redhat/CentOS/Mint</td>
<td class='tty'><em>$WEEWX_ROOT</em>/util/init.d/weewx.redhat</td>
</tr>
</table>
<p>Check the chosen script to make sure the variable <span class="code">WEEWX_ROOT</span>
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&#39;s worth checking). </p>
<p>Copy it to the proper location for your system: </p>
<table class="center" style="width: 90%">
<tr>
<td style="width: 25%">SuSE:</td>
<td class='tty'>cp <em>$WEEWX_ROOT</em>/util/init.d/weewx.suse /etc/init.d/weewx</td>
</tr>
<tr>
<td>Debian/Ubuntu/Mint:</td>
<td class='tty'>cp <em>$WEEWX_ROOT</em>/util/init.d/weewx.debian /etc/init.d/weewx</td>
</tr>
<tr>
<td>Redhat/CentOS/Fedora:</td>
<td class='tty'>cp <em>$WEEWX_ROOT</em>/util/init.d/weewx.redhat /etc/init.d/weewx</td>
</tr>
</table>
<p>Make sure the script is executable: </p>
<table class="center" style="width: 90%">
<tr>
<td style="width: 25%">SuSE:</td>
<td class='tty'>chmod +x /etc/init.d/weewx</td>
</tr>
<tr>
<td >Debian/Ubuntu/Mint:</td>
<td class='tty'>chmod +x /etc/init.d/weewx</td>
</tr>
<tr>
<td >Redhat/CentOS/Fedora:</td>
<td class='tty'>chmod +x /etc/init.d/weewx</td>
</tr>
</table>
<p>Create symbolic links in the run level directories: </p>
<table class="center" style="width: 90%">
<tr>
<td style="width: 25%">SuSE:</td>
<td class='tty'>/usr/lib/lsb/install_initd /etc/init.d/weewx</td>
</tr>
<tr>
<td >Debian/Ubuntu/Mint:</td>
<td class='tty'>update-rc.d weewx defaults 98</td>
</tr>
<tr>
<td >Redhat/CentOS/Fedora</td>
<td class='tty'>chkconfig weewx on</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<br/>
/etc/init.d/weewx stop<br/>
/etc/init.d/weewx restart<br/>
</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, Mint) 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 &quot;Expert&quot; 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 &#39;reload&#39; option: </p>
<p class="tty">/etc/init.d/weewx reload </p>
<h1 id="Monitoring_weewx">Monitoring <span class="code">weewx</span></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>
<pre class='tty'>tail -f /var/log/messages</pre>
<p>Set the debug option in <span class='code'>weewx.conf</span> to
generate many more checks and output more information. This can be
useful for diagnosing problems and debugging.</p>
<pre class='tty'>debug = 1</pre>
<h1 id="Compatibility_with_wview">Compatibility with <span class="code">wview</span></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. This will be done automatically on startup by
<span class="code">weewx</span>.
</p>
<h1 id="Troubleshooting">Troubleshooting</h1>
<p>This section lists some common problems installing and running
<span class="code">weewx</span>. If you are still stuck, be sure to: </p>
<ul>
<li>Set the option <span class="code">debug</span> to
<span class="code">1</span> in <span class='code'>weewx.conf</span>.
This will put much more information in the log file, which can
be very useful for troubleshooting and debugging!
<p><pre class='tty'>debug = 1</pre><br/></p>
</li>
<li><a href="#Monitoring_weewx">Look at the log file</a>. I am always
happy to take questions, but the first thing I will ask you is,
&quot;Did you look at the log file?&quot;
<p><pre class='tty'>tail -f /var/log/messages</pre><br/></p>
</li>
<li>Run from the command line. Generally, <span class="code">weewx</span>
will catch and log any unrecoverable exceptions. But if you are getting
strange results, it is worth running from the command line and looking
for any clues.
<p><pre class='tty'><em>$WEEWX_ROOT</em>/bin/weewx/weewxd.py <em>$WEEWX_ROOT</em>/weewx.conf</pre></p>
</li>
</ul>
<h2>Hardware</h2>
<h3>Establishing connectivity</h3>
<p>If you unable to get anything out of <span class="code">weewx</span>, first
check that you have connectivity to your weather station. For the Davis stations,
you can use a terminal emulator (I like <span class="code">minicom</span> because
it can be run from through a simple TTY connection) to run a simple test. Set
it up to communicate using the appropriate port and baudrate. For example</p>
<p class="tty">minicom -b 19200 -D /dev/ttyUSB0</p>
<p>Then type in <span class="code">TEST</span>, all in capital letters. It will
not echo the characters. Then hit the <span class="code">&lt;enter&gt;</span>
key. It should echo back <span class="code">TEST</span>.</p>
<p>If this works, then you have established connectivity with the Davis and
the problem must lie elsewhere.</p>
<h3>Tips on making a system reliable</h3>
<p>If you are having problems keeping your weather station up for long
periods of time, here are some tips, in decreasing order of importance:
</p>
<ul>
<li>Run on dedicated hardware. If you are using the server for other
tasks, particularly as your desktop machine, you will have reliability
problems. If you are using it as a print or network server, you will
probably be OK.
</li>
<li>Run headless. Modern graphical systems are extremely complex. As new
features are added, test suites don&#39;t always catch up. Your system
will be much more reliable if you run it without a windowing system (X
Windows, in the case of Linux). </li>
<li>Use an Uninterruptible Power Supply (UPS). The vast majority of power
glitches are very short lived — just a second or two — so you do not
need a big one. The 425 VA unit I use to protect my fit-PC cost me $55
at Best Buy. </li>
<li>Use a VantagePro console with a serial connection, not a USB
connection. See the next section for details. </li>
<li>If you do use a USB connection, put a ferrite coil on each end of
the cable to your console. If you have enough length and the ferrite
coil is big enough, make a loop so it goes through the coil twice.
Here's a picture of a Davis Envoy with a ferrite coil not only on the
USB connection (top wire), but also the power supply. Both have loops.
</li>
</ul>
<p align='center'>
<a href="ferrites.jpg"><img src="ferrites.jpg" width='200' border='0' alt="Ferrite coils" longdesc="Cable connection looped through a ferrite coil" /></a>
</p>
<h3>cp2101 converter problems</h3>
<p>The USB converter used in the Davis VantagePro is known to have some &quot;noise&quot;
problems. The symptom is that the Linux kernel will disconnect from your old
USB port claiming &quot;EMI noise&quot;, and reconnect to a new and different
port, where <span class="code">weewx</span> can&#39;t find it. Here&#39;s a
typical log output: </p>
<pre>
Nov 29 10:40:21 hummingbird kernel: [6661624.786792] hub 2-0:1.0: port 3 disabled by hub (EMI?), re-enabling...
Nov 29 10:40:21 hummingbird kernel: [6661624.786871] usb 2-3: USB disconnect, address 2
Nov 29 10:40:21 hummingbird kernel: [6661624.795778] cp2101 2-3:1.0: device disconnected
Nov 29 10:40:21 hummingbird weewx[25808]: VantagePro: Max retries exceeded while getting LOOP packets
... (messages elided)
Nov 29 10:40:22 hummingbird kernel: [6661625.352340] cp2101 2-3:1.0: cp2101 converter detected
Nov 29 10:40:22 hummingbird kernel: [6661625.528107] usb 2-3: reset full speed USB device using ohci_hcd and address 3
Nov 29 10:40:22 hummingbird kernel: [6661625.735497] usb 2-3: cp2101 converter now attached to ttyUSB1</pre>
<p>In this example, the VantagePro was connected to <span class="code">/dev/ttyUSB0</span>,
but then reconnected to <span class="code">/dev/ttyUSB1</span>. </p>
<p>If you put ferrite coils on the USB connection, you will eliminate 90% of
this problem. I did this about 3 years ago, and have not had a problem since.
</p>
<p>However, there is one final step that you can take to really harden up
your system: install a <span class="code">udev</span> script that will create
a symbolic link to the VantagePro USB port, whatever it might be. With this
approach, if the port jumps from <span class="code">ttyUSB0</span> to
<span class="code">ttyUSB1</span>, the symbolic link will follow it. You just
specify port <span class="code">/dev/vpro</span> in the configuration file
<span class="code">weewx.conf</span> and be done with it. </p>
<p>Here's how: </p>
<h4>Installing a udev script</h4>
<p>I have installed a file <span class="code">/etc/udev/rules.d/vpro.rules</span>
on my fit-PC that looks like this: </p>
<pre>
# Automount the VantagePro2 to port /dev/vpro.
# Install in /etc/udev/rules.d/vpro.rules
#
ACTION==&quot;add&quot;, ATTRS{interface}==&quot;CP2102 USB to UART Bridge Controller&quot;, SYMLINK+=&quot;vpro&quot;</pre>
<p>What this rule says is that when the USB port is plugged in (action
<span class="code">add</span>), and it has an attribute with name
<span class="code">interface</span> that is equal to &quot;<span class="code">CP2102
USB to UART Bridge Controller</span>&quot;, then add a symbolic link for its
physical port to <span class="code">/dev/vpro</span>. </p>
<p>Here&#39;s a rule that works for my Serial-to-USB cable, made by Prolific
Technology, Inc.:</p>
<pre>
# Automount Serial-to-USB cable to port /dev/vpro
# Install in /etc/udev/rules.d/cable.rules
#
ACTION==&quot;add&quot;, ATTRS{product}==&quot;USB-Serial Controller&quot;, SYMLINK+=&quot;vpro&quot;</pre>
<p>Your devices may, and probably will, have different identifiers!! I can recommend
this article, &quot;<a href="http://www.reactivated.net/writing_udev_rules.html"><em>Writing
udev rules</em></a>,&quot; for how to find and write an appropriate
<span class="code">udev</span> rule for your controller. (Note, however, that
this article uses the old <span class="code">udevinfo</span> command, rather
than the newer <span class="code">udevadm</span> command.) In particular, run
the command </p>
<pre># udevadm info --attribute-walk --path $(udevadm info --query=path --name=/dev/ttyUSB0) </pre>
<p>where<span class="code"> /dev/ttyUSB0</span> is the port (substitute your
real USB port) the VP2 is attached to. It will print out various identifiers
that can be useful in identifying your VP2 to <span class="code">udev</span>.
While the first example script above used a rule that matched attribute
<span class="code">interface</span>, others are possible. For example, the second
example, for the serial-to-USB cable, chose to match the attribute
<span class="code">product</span>. </p>
<p>Once you&#39;ve installed your <span class="code">udev</span> rule, you can
then set <span class="code">port=/dev/vpro</span> in <span class="code">weewx.conf</span>,
confident that it will always point to your VantagePro2, no matter which USB
port it is actually attached to! </p>
<p>I have tested this system many times. You can yank the USB port out of the
machine and then plug it back in while also pulling out the network connection
in the middle of an FTP upload: <span class="code">weewx</span> will recover.
</p>
<p>Or, at least, it should! </p>
<h3>FreeBSD</h3>
<p>User Fabian reports that the following had to be done to get the VantagePro2
working under FreeBSD:</p>
<pre class="tty">
I needed the uslcom Driver for the usb/rs232 Adapter used by my vantage. Also I had to reset the memory of the weatherstation.
Loading the Driver:
Put uslcom_load=&quot;YES&quot; in /boot/loader.conf (to load it as module).
Which gives here an output like:
uslcom0: &lt;CP2102 USB to UART Bridge Controller&gt; on usbus1
And put in weewx.conf:
port = /dev/cuaU0</pre>
<h3>Weewx generates HTML pages, but it does not update them</h3>
<p>If you are getting a symptom that everything appears normal, that is HTML
is getting generated and getting FTP&#39;d to your webserver <em>(look in the
log to be sure</em>!), but your web pages are not being updated, it could be
because the data on board your console has gotten garbled. The way the Davis
Vantage series works is that the software (<span class="code">weewx</span> in
this case) asks the console for all archive data &quot;since&quot; some time.
The console then downloads the records one at a time. After it gets to the very
last one, the memory wraps around, and the timestamp will suddenly jump backwards
in time a couple weeks &mdash; the software knows it has downloaded the last
record and stops.</p>
<p>However, if the internal memory gets garbled, the console will immediately
return archives in the past, and so it looks like the timestamps have decreased
in value and so <span class="code">weewx</span> figures that&#39;s it: there&#39;s
no more data.</p>
<p>I have received reports from a couple of users who have had this problem.
There seems to be two fixes:</p>
<ol>
<li>Unplug the console, take out the batteries, and wait a minute or two.
This will cause the console software to internally reboot. In one case this
has fixed the problem without data loss.</li>
<li>If all else fails, clear the memory of the console using the utility
<span class="code">config_vp.py</span>. This may cause loss of data, but
usually works. Adjust paths as necessary:</li>
</ol>
<p class="tty">cd /home/weewx<br />
./bin/config_vp.py weewx.conf --clear </p>
<h3>3rd party Vantage connectors</h3>
<p>This section is for those who are using a homebrew or 3rd party connector
to a Davis Vantage console that does not contain a logger, such as the
<a href="http://www.wxforum.net/index.php?topic=14063.0">DSI-01 serial interface</a>.
That is, it is a pure serial connection to the console, with no onboard memory.
</p>
<p>For these interfaces, you must set record generation to <em>software</em>.
Without this information, <span class="code">weewx</span> is unable to detect
the absence of onboard memory. If you do not do this, you will get errors that
look like the following in your syslog:</p>
<pre class="tty">
Nov 27 20:30:21 raspberrypi weewx[5607]: reportengine: Caught unrecoverable exception in generator weewx.filegenerator.FileGenerator
Nov 27 20:30:21 raspberrypi weewx[5607]: **** 'NoneType' object has no attribute '__getitem__'
Nov 27 20:30:21 raspberrypi weewx[5607]: **** Traceback (most recent call last):
Nov 27 20:30:21 raspberrypi weewx[5607]: **** File "/home/weewx/bin/weewx/reportengine.py", line 132, in run
Nov 27 20:30:21 raspberrypi weewx[5607]: **** obj.start()
Nov 27 20:30:21 raspberrypi weewx[5607]: **** File "/home/weewx/bin/weewx/reportengine.py", line 259, in start
Nov 27 20:30:21 raspberrypi weewx[5607]: **** self.run()
Nov 27 20:30:21 raspberrypi weewx[5607]: **** File "/home/weewx/bin/weewx/filegenerator.py", line 41, in run
Nov 27 20:30:21 raspberrypi weewx[5607]: **** self.setup()
Nov 27 20:30:21 raspberrypi weewx[5607]: **** File "/home/weewx/bin/weewx/filegenerator.py", line 52, in setup
Nov 27 20:30:21 raspberrypi weewx[5607]: **** self.initAlmanac(self.gen_ts)
Nov 27 20:30:21 raspberrypi weewx[5607]: **** File "/home/weewx/bin/weewx/filegenerator.py", line 87, in initAlmanac
Nov 27 20:30:21 raspberrypi weewx[5607]: **** rec = self.getRecord(archivedb, celestial_ts)
Nov 27 20:30:21 raspberrypi weewx[5607]: **** File "/home/weewx/bin/weewx/filegenerator.py", line 115, in getRecord
Nov 27 20:30:21 raspberrypi weewx[5607]: **** record_dict_vt = weewx.units.dictFromStd(record_dict)
Nov 27 20:30:21 raspberrypi weewx[5607]: **** File "/home/weewx/bin/weewx/units.py", line 892, in dictFromStd
Nov 27 20:30:21 raspberrypi weewx[5607]: **** std_unit_system = d['usUnits']
Nov 27 20:30:21 raspberrypi weewx[5607]: **** TypeError: 'NoneType' object has no attribute '__getitem__'
Nov 27 20:30:21 raspberrypi weewx[5607]: **** Generator terminated...
Nov 27 20:30:23 raspberrypi weewx[5607]: genimages: Generated 11 images in 2.53 seconds</pre>
<p>See the section on option <span class="code">
<a href="#record_generation">record_generation</a></span>.</p>
<h2>Software</h2>
<h3><span class="code">configobj</span> errors</h3>
<p>These are errors in the configuration file. Two are very common. Incidentally,
these errors are far easier to diagnose when <span class="code">weewx</span>
is run from the command line. </p>
<h4><span class="code">configobj.DuplicateError</span> exception</h4>
<p>This error is caused by using an identifier more than once in the configuration
file. For example, you may have inadvertently listed your FTP server twice:
</p>
<pre>
[Reports]
[[FTP]]
... (details elided)
user = fred
server = ftp.myhost.com
password = mypassword
server = ftp.myhost.com # OOPS! Listed it twice!
path = /weather
... </pre>
<p>Generally, if you encounter this error, the log file will give you the line
number it happened in: </p>
<pre>
Apr 24 12:09:15 raven weewx[11480]: wxengine: Error while parsing configuration file /home/weewx/weewx.conf
Apr 24 12:09:15 raven weewx[11480]: wxengine: Unable to initialize main loop:
Apr 24 12:09:15 raven weewx[11480]: **** Duplicate keyword name at line 254.
Apr 24 12:09:15 raven weewx[11480]: **** Exiting. </pre>
<h4><span class="code">configobj.NestingError</span> exception</h4>
<p>This is a very similar error, and is caused by a misformed section nesting.
For example: </p>
<pre>
[Reports]
[[FTP]]]
... (details elided)</pre>
<p>Note the extra closing bracket on the subsection <span class="code">FTP</span>.
</p>
<h3>No barometer data</h3>
<p>If everything appears normal except that you have no barometer data, the
problem may be a mismatch between the unit system used for service
<span class="code">StdConvert</span> and the unit system used by service
<span class="code">StdQC</span>. For example:</p>
<p class="tty">
[StdConvert]<br />
&nbsp;&nbsp;target_unit = METRIC<br />
<br />
...<br />
<br />
[StdQC]<br />
&nbsp;&nbsp;[[MinMax]]<br />
&nbsp;&nbsp;&nbsp;&nbsp;barometer = 28, 32.5</p>
<p>The problem is that you are requiring the barometer data to be between 28
and 32.5, but with the unit system set to <span class="code">METRIC</span>,
the data will be in the range 990 to 1050 or so!</p>
<h3><span class="code">Cheetah.NameMapper.NotFound</span> errors</h3>
<p>If you get errors of the sort: </p>
<pre>
Apr 12 05:12:32 raven reportengine[3074]: filegenerator: Caught exception &quot;&lt;class &#39;NameMapper.NotFound&#39;&gt;&quot;
Apr 12 05:12:32 raven reportengine[3074]: **** Message: &quot;cannot find &#39;fubar&#39; in template /home/weewx/skins/Standard/index.html.tmpl&quot;
Apr 12 05:12:32 raven reportengine[3074]: **** Ignoring template and continuing.</pre>
<p>you have a tag in your template that <span class="code">weewx</span> does
not recognize (in this example, it&#39;s the tag <span class="code">$fubar</span>
in the template <span class="code">/home/weewx/skins/Standard/index.html.tmpl</span>.
</p>
<h1 id="Architectural_notes">Architectural notes</h1>
<p>This section is not needed to get started. </p>
<h2>Goals</h2>
<p>The primary design 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>Extensibility. Make it easy for the user to add new features or to modify
existing features.</li>
<li>&quot;Fast enough.&quot; In any design decision, architectural simplicity
and elegance trump speed. </li>
<li>One code base. The same code base should be used for all platforms,
all weather stations, all reports, and any combination of features. Ample
configuration and customization options should be provided so the user doesn&#39;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&#39;t have
to go chase them down all over the Web before getting started. </li>
<li>Support only the Davis VantagePro2 initially (that&#39;s what I have),
but make no architectural decisions that lock out other stations. </li>
<li>As &quot;pythonic&quot; as I know how to make it. I&#39;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>Strategies</h2>
<p>To meet these goals, the following strategies were used: </p>
<ul>
<li>A &quot;micro-kernel&quot; design. The <span class="code">weewx</span>
engine actually does very little. Its primary job is to load and run <em>
services</em> at runtime, making it easy for users to add or subtract features.
</li>
<li>A largely stateless design style. For example, many of the processing
routines read the data they need directly from the database, rather than
caching it and sharing with other 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>Isolate the data collection and archiving code in a single thread that
is simple enough that it is unlikely to crash. The report processing is
where most mistakes are likely to happen, so isolate that in a separate
thread. If it crashes, it will not affect the main data thread. </li>
<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>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 <span class="code">weewx</span> 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 &quot;Current
Conditions&quot; page takes just under 2 seconds (compared with
0.4 seconds for <span class="code">wview</span>). </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.X versions until V3.X is so widespread
it cannot be ignored, then make a permanent switch. Given the slow adoption
rate of V3.X this is unlikely to happen anytime soon. In any case, I doubt the
transition 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 &quot;<span class="code">/etc/init.d/weewx
stop</span>&quot; 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 &quot;hard&quot; 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 due to its simplicity), then this causes program termination. If
it happens in the report processing thread (much more likely), then only the
generation of reports will be affected — the main thread will continue downloading
data off the instrument and putting them in the database. You can fix the problem
at your leisure, without worrying about losing any data. </p>
<h2>Terminology</h2>
<p>This is a glossary of terminology used throughout the code. </p>
<table style="width: 100%">
<tr>
<td class="text_highlight"><strong>Name</strong></td>
<td><strong>Description</strong></td>
</tr>
<tr>
<td class="text_highlight">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 class="text_highlight">record</td>
<td>Something obtained off the SQL database. </td>
</tr>
<tr>
<td class="text_highlight">archive packet</td>
<td>A packet obtained off the store on the weather station. For example,
with a Davis VantagePro, it&#39;s obtained using the
<span class="code">DMPAFT</span> command. </td>
</tr>
<tr>
<td class="text_highlight">loop packet</td>
<td>A packet with the current observations. For example, with a Davis
VantagePro, it&#39;s obtained using the <span class="code">LOOP</span>
command. </td>
</tr>
<tr>
<td class="text_highlight">archive record</td>
<td>A record obtained off the SQL database</td>
</tr>
<tr>
<td class="text_highlight">tuple-time</td>
<td>An instance of the Python object <span class="code">
<a href="http://docs.python.org/2/library/time.html#time.struct_time">
time.struct_time</a></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">
<a href="http://docs.python.org/2/library/time.html">time</a></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 class="text_highlight">epoch time</td>
<td>Sometimes referred to as &quot;unix time,&quot; or &quot;unix epoch
time.&quot; 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 in the
databases and appears as type <span class="code">dateTime</span>
in the SQL schema, perhaps an unfortunate name because of the similarity
to the completely unrelated Python type <span class="code">datetime</span>.
Very easy to manipulate, but it&#39;s a big opaque number. </td>
</tr>
<tr>
<td class="text_highlight">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 class="text_highlight">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 class="text_highlight">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 class="text_highlight">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>
<tr>
<td class="text_highlight">value tuple</td>
<td>A 3-way tuple. First element is a value, second element the unit
type the value is in, the third the unit group. An example would be
<span class="code">(21.2, &#39;degree_C&#39;, &#39;group_temperature&#39;)</span>.</td>
</tr>
<tr>
<td class="text_highlight">db_dict</td>
<td>A dictionary with all the data necessary to bind to a database.
An example for sqlite would be <span class="code">{&#39;driver&#39;
: &#39;db.sqlite&#39;, &#39;root&#39;:&#39;/home/weewx&#39;, &#39;database&#39;:&#39;archive/weewx.sdb&#39;}</span>,
an example for MySQL would be <span class="code">{'driver' : 'db.mysql',
'host': 'localhost', 'user' : 'weewx', 'password' : 'mypassword', 'database'
: 'weewx'}</span>.</td>
</tr>
</table>
<h2>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 Vantage series supports
only U.S. Customary units internally. The Oregon Scientific WMR-USB series
uses an odd mix of US and metric.</li>
<li>In the database. Either US or Metric can be used.</li>
<li>In the presentation (i.e., html and image files). </li>
</ol>
<p>The general strategy is that measurements are converted by service
<span class="code">StdConvert</span> as they come off the weather station into
a target unit system, then stored internally in the database. Then, as they
come off the database to be used for a report, they are converted into a target
unit, specified by the skin. </p>
<h2>Value &quot;<span class="code">None</span>&quot;</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>Time</h2>
<p><span class="code">Weewx </span>stores all data in UTC (roughly, &quot;Greenwich&quot;
or &quot;Zulu&quot;) 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,
then things get a bit more complicated. 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)<br/>
delta = datetime.timedelta(seconds=10800)<br/>
next_dt = time_dt + delta<br/>
next_ts = int(time.mktime(next_dt.timetuple()))<br/>
</p>
<p>Other time conversion problems are handled in a similar manner. </p>
<p class='copyright'>
&copy; <a href='copyright.htm'>Copyright</a> Tom Keffer
</p>
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