Powering off Raspberry Pi without proper shutdown could cause SD card corruption and force users to re-flash SD cards time to time.
By using this feature NanoDLP listens to GPIO if state of GPIO changed to the required state, it will shutdown the printer during the idle mode and during the print it will stop the printer.
How to use graceful shutdown?
To complete power-off it is possible to use Raspberry Pi kernel parameters (config.txt) to let external controller know that Pi is switched off. So it can cut the power completely. GPIO state changes just after complete Raspberry Pi shutdown.
Drives a GPIO high or low on poweroff (including halt). Enabling this overlay will prevent the ability to boot by driving GPIO3 low.
GPIO for signalling (default 26)
Set if the power control device requires a high->low transition to trigger a power-down. Note that this will require the support of a custom dt-blob.bin to prevent a power-down during the boot process, and that a reboot will also cause the pin to go low.
Set if the gpio pin should be configured as an input.
Set to export the configured pin to sysfs
Specify (in ms) how long the kernel waits for power-down before issuing a WARN (default 3000).