This is a collections of Python plugin for Collectd.

• cpu_temp.py: Report the CPU temperature. Tested on a Raspberry Pi 3.
• sht21_kernel.py/sht21_usermode.py: Measure temperature and relative humidity from a Sensirion SHT21 sensor connected via I²C. Calculate dew point and absolute humidity. Tested on a Raspberry Pi 3.
• mcp3425.py: Measure voltage using an MCP3425 analog-digital converter.

For more information, please refer to my blogpost.

Copy the desired Python files to your target system. Then add the module to your collectd.conf. Make sure to adjust the ModulePath value. The following example assumes the plugins were copied to /opt/collectd_plugins.

If your CPU temperature cannot be read from /sys/class/thermal/thermal_zone0/temp, make sure to adjust that variable too.

LoadPlugin python
<Plugin python>
    ModulePath "/opt/collectd_plugins"
    Import "cpu_temp"
    <Module cpu_temp>
        Path "/sys/class/thermal/thermal_zone0/temp"
    </Module>
</Plugin>

For this plugin to work, the sht21 kernel module must be loaded:

echo "sht21" > /etc/modules-load.d/sht21.conf

There are currently no configuration options available.

LoadPlugin python
<Plugin python>
    ModulePath "/opt/collectd_plugins"
    Import "sht21_kernel"
</Plugin>

Same as sht21_kernel, but it does not require the sht21 kernel module.
The downside of the user-mode plugin is that it does not allow concurrent access. As workaround, you can specify a lock file shared by concurrent applications.

LoadPlugin python
<Plugin python>
    ModulePath "/opt/collectd_plugins"
    Import "sht21_sht21_usermode"
    <Module sht21_usermode>
        LockFile "/var/run/lock/sht21.lock"
    </Module>
</Plugin>

The plugin assumes that you're using three voltage divider resistors to bring the voltage into a measurable range. You can configure them in the Python script.

There are currently no configuration options available.

LoadPlugin python
<Plugin python>
    ModulePath "/opt/collectd_plugins"
    Import "mcp3425"
</Plugin>

MIT License, see LICENSE file.