The /config folder holds all runtime configuration files that can be used by the compiled executables. It normally has to be shipped along side the executables.
Application settings are configured using either *.toml files or environment variables (which have precedence over file-based configuration). They are loaded using cleanenv and follow the structure defined in the common package's config.go file. default.toml is both an example configuration file where everything that was commented out is an optional setting with the respective default values. LED group configuration has to always be supplied in the configuration file as it has no sensible default value and is not really fit to map to environment variables.
A device tree config to initialize the PCF2574 I²C-GPIO-expanders, used to add additional buttons and other inputs, is included in this repository. It can be activated from the project root using the the dtoverlay tool, e.g. for two expanders with the I²C addresses 0x20 and 0x21 that have their interrupt lines connected to GPIO17 and GPIO27:
sudo dtoverlay -d ./config/device-tree/ gpio-expander addr=0x20 irq=17
sudo dtoverlay -d ./config/device-tree/ gpio-expander addr=0x21 irq=27For the interrupts to work correctly on an Raspberry Pi you may have to activate the internal pull ups for these pins by adding the following line to your /boot/config.txt:
gpio=17,27=ip,puAfter changes to the gpio-expander.dts source, it has to be recompiled using dtc (install using sudo apt install device-tree-compiler):
dtc -O dtb -o config/device-tree/gpio-expander.dtbo config/device-tree/gpio-expander.dtsTo permanently apply the device tree overlays for usage, copy the compiled gpio-expander.dtbo file to /boot/overlays/ and add the following lines to the /boot/config.txt as well:
dtoverlay=gpio-expander,addr=0x20,irq=17
dtoverlay=gpio-expander,addr=0x21,irq=27