USB-WDE1 Munin plugin
=====================
Generate graphs for temperature and humidity by utilizing Munin.


Idea
----
0. Keep a logfile with the most recent single line
1. Use the munin plugin to generate munin-compatible data from the log file


Setup
-----
0. Checkout the munin plugin code:
   $ cd /usr/local/src
   $ git clone git://git.cweiske.de/usb-wde1-tools.git
   $ cd usb-wde1-tools

1. A process needs to watch the USB interface and log the last
   line with temperature data into a log file.
   You can do that manually with
   $ socat /dev/ttyUSB0,b9600 STDOUT |./munin/log-single-line.sh test.log

   The most easy way is to run
   $ cd munin && nohup ./usb-wde1-log-last.sh &
   once. It backgrounds the logging process and logs into /tmp/usb-wde1-last.
   This process needs to be started whenever the machine is rebooted.

2. Link the munin plugin:
   $ cd /etc/munin/plugins
   $ ln -s /usr/local/src/usb-wde1-tools/munin/usb-wde1_ usb-wde1_temperature
   $ ln -s /usr/local/src/usb-wde1-tools/munin/usb-wde1_ usb-wde1_humidity

3. Configure the plugins
   Edit /etc/munin/plugin-conf.d/munin-node and add the following lines:
   [usb-wde1_*]
   env.logfile /tmp/usb-wde1-last
   env.host_name House
   env.sensors 0 1 7
   env.sensor0 Living room
   env.sensor1 Kitchen
   env.sensor7 Outside

4. Try it:
   $ munin-run usb-wde1_temperature autoconf
    - should echo "yes"
   $ munin-run usb-wde1_temperature config
    - should display the plugin configuration with all environment variables
      set
   $ munin-run usb-wde1_temperature
   $ munin-run usb-wde1_humidity
    - should display the current values from the log file

5. You are done - enjoy.



Debugging & Development
-----------------------
The dummy data generator is a small php script that generates log lines
as they would come from the usb-wde1 usb port:
$ ./dummy-data-generator.php |./munin/log-single-line.sh test.log

Local (non-installed) plugin setup:
$ cd munin
$ ln -s usb-wde1_ usb-wde1_temperature
$ ln -s usb-wde1_ usb-wde1_humidity
$ cd ..


Running the munin plugin for development purposes is also relatively easy
since you can pass the environment configuration variables
from the munin configuration on the command line:
$ logfile=test.log sensors="0 1 7" ./munin/usb-wde1_temperature

When you have problems running the munin plugin, try to
remove the line 
 env.host_name House
from file usb-wde1_


Permission errors
.................

    cu: open (/dev/ttyUSB0): Permission denied
    cu: /dev/ttyUSB0: Line in use

Only way that I found to fix this was change ownership of `/dev/ttyUSB0` to uucp::

     $ chown uucp /dev/ttyUSB0