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 /var/spool/usb-wde1/usb-wde1-last. This process needs to be started whenever the machine is rebooted.

   The systemd/ directory contains a usb-wde1-log.service file you can copy to /etc/systemd/system/. After copying it, run:

   $ systemctl daemon-reload
   $ systemctl start usb-wde1-log
   $ systemctl status usb-wde1-log
   $ systemctl enable usb-wde1-log
   

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 /var/spool/usb-wde1/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

HTML/Plain text output

You may use htmlreport/gen-html.php to generate HTML or plain text files with the temperature and humidity information.

Install PHP and the PHP rrd extension (pear install pecl/rrd) to make it work.

Run gen-html.php every 5 minutes.

Static USB device name

When you have multiple serial USB devices attached to the computer, rebooting may lead to switched ttyUSB* numbers.

A solution is to define a udev rule in /etc/udev/rules.d/99-usb-wde1.rules:

SUBSYSTEM=="tty", ATTRS{serial}=="XQJ2EJEMADDFYBD3", SYMLINK+="usbwde1"

You can find the serial number in dmesg output:

usb 1-3: new full-speed USB device number 2 using xhci_hcd
usb 1-3: New USB device found, idVendor=10c4, idProduct=ea60, bcdDevice= 1.00
usb 1-3: New USB device strings: Mfr=1, Product=2, SerialNumber=3
usb 1-3: Product: ELV USB-WDE1 Wetterdatenempfänger
usb 1-3: Manufacturer: Silicon Labs
usb 1-3: SerialNumber: XQJ2EJEMADDFYBD3

After creating the file, activate it:

$ udevadm control --reload
$ udevadm trigger

Now a file /dev/usbwde1 exists.

Modify munin/usb-wde1-log-last.sh to use the new device file instead of ttyUSB0.