@cremeikas: thank you very much for providing the implementation.
@Stril: depending on what version of hardware you have: if you have OSPi, it’s very easy to modify the code, and then just run the ./build.sh to re-compile the firmware after modification.
If you have the microcontroller-base OpenSprinkler (either AC or DC version), here are the instructions on how to compile:
https://opensprinkler.freshdesk.com/solution/articles/5000165132-how-to-compile-opensprinkler-firmware
I admit it’s quite technical, but just follow the instructions closely, and you should be able to get it to work.