Taking some rest, physically exhausted ... but not mentally.
So I worked on the automation and the watering controller.
I first wanted to go with OpenSprinkler. But I found it pretty well undocumented, and changing hardware on each version.
Well, better to do things by myself.
I went with ESPEasy, no need to write Arduino code, a simple rule would make it.
I will detail a bit more everything in a detailled post about how to reproduce what I've done.
Technically, it's an ESP8266 (Nodemcuv3) with an I2C Expander (MCP23017) controlling relays and a OLED Screen.
It is possible thanks to the buttons to manually control the relays, it activate a relay for 30 min (but can be manually toggled).
I also have events listening on HTTP API to send through my home automation an event to start/stop a zone for an amount of seconds.
On reset, it closes all the relays. And when there's no power, valves are closing by themselves.
It's currently on a breadboard for proof of concept. I will solder everything properly once I will test the valver with the AC/DC transformer.