Setup Pimoroni OnOff SHIM using Device Tree Overlays

The OnOff SHIM by Pimoroni is a convenient power switch for the Raspberry Pi. The official guide suggests to install a daemon that initiates a clean shutdown on button press. A much simpler solution is to use device tree overlays and avoid 3rd-party tools. Furthermore, the "old" daemon solution does no longer work on Debian Bookworm based distributions and is a using sysv-based init script.

Given the pin-out of the shim, the solution is to watch PIN 17 and initiates a clean shutdown on press button (pulled low). And just before the Pi shuts down, PIN 4 gets pulled low to cut the power. Enabling is as easy as adding this to /boot/firmware/config.txt and reboot:

dtoverlay=gpio-shutdown,gpio_pin=17,active_low=1,gpio_pull=up
dtoverlay=gpio-poweroff,gpiopin=4,active_low=1

Please check https://github.com/raspberrypi/firmware/blob/master/boot/overlays/README for further details. This solution works on Raspberry Pi OS 12 (Debian Bookworm based) and a Raspberry Pi Zero or later.