*2.1. Design and Development of the IoT Node*

The IoT node was designed and developed using Arduino architecture (Figure 1), as it has a very low price for all the components needed for developing a low cost IoT system. A typical wireless node consists of a microcontroller that is also capable of performing data processing; the transceiver, which is responsible for the wireless communication; the power source; and finally the various circuits needed (e.g., AD converters) for supporting the reading of analog and digital signals of the sensors and the actuators. To implement the node, a board was developed by splitting it into 4 distinct layers:


**Figure 1.** IoT node architecture.

The node (Figure 2) has a small size of 12 × 8 cm and IP67 protection so that it can be used in a large number of applications in harsh environments. Moreover, it supports both analog and digital sensors and various communication protocols (e.g., RS-485 serial communication protocol) for supporting most of the available sensors/actuators (even industrial ones).

**Figure 2.** IoT node implementation.

Data can be uploaded using general (GPRS and 4G) or low-power (NB-IoT and LTE-M) cellular network communication protocols. The communication between the node and the

cloud was bidirectional in order to enable remote control and configuration of the system (e.g., open/close valve), and it achieved almost real-time measurements with a minimum sampling rate of 30 s.

To avoid the configuration process on behalf of the user, making the system "plug and play" and able to work with the simple click of the start button, it was decided that the developed node should also act as a getaway node, with direct communication to the cloud. Using this methodology, the nodes were preconfigured, while the cloud services were developed in such way to make them capable to automatically understand the type of the sensors connected to each node.

### *2.2. Reduction in Power Consumption*

The power consumption of an IoT system is a quite critical parameter, as there are cases in which sensors have to be placed into dense and high crops (e.g., maize), where the charging of batteries is a difficult task. To minimize the power consumption of the node, 3 different prototypes were developed. The first one was developed using a commercial Arduino board, while the second was developed by designing a custom board for reducing power consumption. The third one (Figure 2) was an update of the second prototype, which was developed by enhancing the board design for minimizing the power consumption even more.
