fanshim-cpp

C++ driver code for the fanshim on raspberry pi using libgpiod

pimoroni link

Warning/disclaimer:

very experimental code, for testing purposes only.

[may not work at any time or even cause hardware damage (e.g. from causing the fan to be constantly running)].

Only proceed if you know what the code is doing.

Credits

• official fanshim controller code https://github.com/pimoroni/fanshim-python
• nlohmann/json https://github.com/nlohmann/json/

Build

• If not installed: get the libgpiod-dev library
• Put the json.hpp file from https://github.com/nlohmann/json/releases in the same folder as the source code, tested with 3.7.0
• Compile with clang++ fanshim_driver.cpp -o fanshim_driver -O3 -std=c++17 -lstdc++fs -lgpiodcxx (may also work with g++)

Example systemd service file

Change /path/to/compiled/binary to the compiled binary path.

[Unit]
Description=Fanshim C++ driver

[Service]
ExecStart=/path/to/compiled/binary
Restart=always
RestartSec=5

[Install]
WantedBy=multi-user.target

Configuration

The configuration file is in /usr/local/etc/fanshim.json, example:

{
   "on-threshold": 60,
   "off-threshold": 50,
   "delay": 10
}

Will use the value in the file to override the defaults, no need to specify all keys, just the ones you want to change. Keys used:

• on-threshold/off-threshold: temperature, in Celsius, the threshold for turing on (off) the fan. Default to 60 and 50 respectively.

• delay: in seconds, the program will wait this amount of time before checking the temperature again. Default to 10.

• budget: an integer n, the program will only turn on/off the fan if the temperature is consecutively above (below) the on (off) threshold for the last n temperature measurements. Defaults to 3.

• brightness: an integer from 0 to 31, LED brightness, 0 means no LED (default).

• blink: an integer in [0, 1 , 2], where

  • 0: no blink (default);
  • 1: the LED will blink when the fan is not spinning;
  • 2: the LED will "breath" when the fan is not spinning, the max brightness in this mode is breath_brgt (default 10).

Notes/todo

• No button support (I think given the small size of the button, it'll be easier to force the fan on/off through software based on e.g. whether a certain file exists. Currently, the file is hard-coded as /usr/local/etc/.force_fanshim: fan will be on if this file exists)

Additional features

• Will output current status to the file /usr/local/etc/node_exp_txt/cpu_fan.prom so that it can be used with external programs to monitor, e.g. node_exporter + prometheus + grafana: