The plan is to control solenoid valves to water different areas with necessary quantity.

Currently, I'm able to control 8 relays via the Omega console, which means I could control the valves.
Next, I'm going to write a Python script to switch the relays. At first, I'll just schedule it using a cron-job.

Question: Should I put 1kOhm resistors between Omegas GPIO's and the relay control inputs to protect the Omega against current peaks?

Up to now it has been 2 hours of great fun!

Here is my plan:

Step 1

• water 5 different zones on a fixed schedule

Step 2

• let Omega decide to skip watering based on weather API current conditions and today's rain probability

Step 3

• read cistern water level and switch to tap water if needed

Step 4

• delay watering if it is likely to rain tomorrow and cistern level is below a threshold

Step 5

• Build a nice mobile web frontend with AngularJS with stats and manual-watering-button [water now!]

Further steps

• refine decision model, like to check if it actually rained as forecasted, via API
• add an earth moisture sensor
• learning function for cistern size
• learn watering frequency and quantity based on manual oversteer or user feedback - let's see

Hardware available

• Omega 2+ and Power Dock
• 8-Channel 5V Relay Module with Opto Isolated inputs
• Gardena solenoid valves (24V AC)
• 24V DC power supply unit
• 24V to 5V voltage converter with micro USB
• cistern (4,5m³) to collect rain water
• a bunch of water tubes and wires
• Gardena lawn sprinklers and underground drippers
• Ultrasonic Sensor HC-SR04 to get water level in cistern

Hardware considered

• flowmeter (any recommendations? I don't want leakage underground, should be frost-resisting, accuracy isn't important)
• Arduino Dock to read Ultrasonic sensor
• Moisture sensor

Photos will follow!

I switched to the Arduino Dock. Do I get the documentation right, that most of the GPIOs aren't available because they are used to communicate with the "Arduino"?

"By default, the Serial, SPI, and I2C pins implement these communication protocols and cannot be used as GPIOs. Similarly, the I2S and PWM pins are set to GPIO mode by default." Source

Which results in 6 GPIO left, right? 0,1,2,3,11,18

I switched to the Arduino Dock. Do I get the documentation right, that most of the GPIOs aren't available because they are used to communicate with the "Arduino"?

"By default, the Serial, SPI, and I2C pins implement these communication protocols and cannot be used as GPIOs. Similarly, the I2S and PWM pins are set to GPIO mode by default." Source

Which results in 6 GPIO left, right? 0,1,2,3,11,18

Almost right.

Omega2(+) is acessing the inside flash via the hardware SPI pins, these pins are not used by the Arduino Dock 2 (the on board ATmega328P).

If you do not want to communicate serially with Arduino via UART1 then RX1 and TX1 are free.
The GPIO15, GPIO16 and GPIO17 pins are in use only if Omega2(+) programms (ie uploads a sketch) the ATmega328P.
So you could use these pins via the on board bidirectional level shifter at 5V logic level on the Arduino Dock 2.

Unofficial Arduino Dock 2 schematic

Wrote setup.sh to setup multiplexed GPIOs. Which is a little bit a shoot in the dark. I find it difficult to turn from GPIO Groups to GPIO Numbers to use.

Thanks, György I also use GPIO 45 and 46 now.
Problem: Omega 2+ won't boot if a relay control pin is connected to GPIO 1.
Currently connected GPIOs to the relais: 0 2 3 11 18 45 46

Wrote a Valve class to control the relay (and open the valves) and a little script to test/play with the relais.

I'd love to get comments!

PS: How to add code with highlighting and indention here?

PS: How to add code with highlighting and indention here?

Blocks of code are fenced by lines with three back-ticks ``` in Markdown.
See also the COMPOSE button at the top right corner of the edit frame please

btw. is there any project going on to write a Ruby wrapper for GPIO interaction?

Still not watering anything, but ...
I went ahead in Ruby and found myself writing a 'wrapper' to switch my valves (basically GPIO's). I could contribute if there is any project.

See GitHub Repo

      stdin, stdout, stderr = Open3.popen3("fast-gpio set #{@gpio_number} #{v}")
      if stderr.gets
        raise(OnionGpioWrapperError, stderr.gets)
      end