The main node is the central processing unit of an IoT system.

- The main node periodically requests sensor nodes that are under its control to collect environmental conditions inside farms and send the collected data back to itself.

- Based on the sensor readings, the main node will control on/off related equipment (such as irrigation systems, fans, lights...) to regulate the environmental conditions if the system runs at the automatic operational mode.

- The main node then sends the data collected from sensor nodes to the IoT cloud platform for the functionalities of data communications, data storage, data visualization, and data analysis.

- The main node also controls operational modes of the IoT system:

+ Auto mode: The main node automatically regulates environmental conditions inside farms based on the collected sensor data and pre-defined rules.

+ Timer-based mode: The main node automatically turn on/off related equipment on farms based on the pre-set timer.

+ Manual mode: Farms control equipment on farms via a smartphone application. The man node receives commands from the application and then turns on/off related equipment on farms.