I am developing a aeroponics type system which has multiple stacks. Each stack has multiple trays which house the growing plants. I am going to use the Pi 4 as a main control station from where i can control, modify and monitor all processes. To control the operation of the water pumps and nutrient pumps, LEDs, ultrasonic foggers, etc i have decided to add micro-controller (Pi Pico) to the stacks. The Pi 4 will communicate the instructions to the Pico, but i cannot figure which communication protocol/method is the best (I2C, PCI, CAN, IEEE 1394)?
To make it more clear, the Pi 4 will interface with the Pico(s) and the Pico in turn will control the operation of the stack.