Drafting the specification..

Here are the specifications, that may change or be adapted in the future.

- Monitoring: Temperature, Air humidity, Luminosity, plant soil humidity, Atmospheric pressure
- Watering system that can be triggered by scenarios (soil moisture level) or manually
- Open source

Sensors data have to be accessible from PC and mobile (web browser) and from outside (internet).
Plants are outdoor so sensors data have to be reported wirelessy.
No main power where the plants are. Project has to run on battery.

The microcontroller needs to have the followings:
- I2C capable (sensors reading)
- Analog capable (soil sensor reading)
- Wifi capable
- Cheap
- Evolutive
- Low power consumption

For those reasons I choose the microcontroller ESP8266 / ESP12E.

I have decided, for pratical reason, to make 2 ESP "modules":
- One that will regulary check the sensors and report the value over wifi.
- A second one that  will control the water.
This will probably evolve and I may reconsider to have 2 modules instead of one.

Data collecting: DOMOTICZ
As I already have at home a Raspberry Pi that is running Raspian, I thought that I could use an open source domotic tool.
I have tried couple of them and made by choice with Domoticz. This can be also reconsidered and should not be that hard as many domotic softwares use standart protocol such as MQTT.