# A Novel Plug-in Board for Remote Insect Monitoring
## 2 Materials and Methods
### Communication Modules  
On the plug-in board, there are two communication modules (Figure 2). The first one is the SIM7600E-H, and the second one is the EMB-LR1276S. The SIM7600E-H allows information exchange via different telecommunication networks, including LTE (Long-Term Evolution). All functionalities of the module are available through 87 pads, which are located on the perimeter of the 30 \(\times\) 30 \(\times\) 2.9 mm module. There are 4 dedicated pads for voltage input (but only 2 need to be used) and several pads for ground. The module's supply voltage is between 3.4 and 4.2 V, where 3.8 V is recommended. The power supply must be able to provide more than 2 A current. Out of the pads, three pads can be used to connect external antennas: main, auxiliary, and GNSS (Global Navigation Satellite System). Many of the pads are used as communication or control channels in the different serial communication interfaces, such as UART, SPI, I2C, and USB. Out of the serial communication interfaces, we utilized only the UART. This interface is used as an AT command and data stream channel. The module has 7 pads to the UART interface, including pads to the RTS/CTS hardware handshake. It supports an adjustable haud rate (from 300 bps to 4 Mbps), where the default is 115,200 bps. In our circuit, only the transmitter and receiver lines are connected to the Raspberry Pi's UART interface. However, the Pi's UART interface operates at the 3.3 V voltage level, while the SIM7600's UART is a 1.8 V voltage interface. In this case, a level shifter needs to be used. In most cases, engineers apply a voltage-matching IC (Integrated Circuit), such as the TXB0108 RGYR from Texas Instruments. In contrast, we recommend another level shifter circuit due to its simplicity and cost efficiency (Figure 3). The SIM7600E-H module can be used not just for information transmission but also for time synchronization and for global positioning thanks to the GNSS engine. Before using GNSS, we need to configure it in the proper operating mode with the AT command. It merges satellite and network information for high availability and accuracy. In addition, it offers industrial accuracy and performance. The key features of the GNSS engine are listed below [21]:  
* Accuracy (Open Sky): 2.5 m;
* TTFF (Open Sky): \(\sim\)35 s (cold start);
* Update rate: 1 Hz;
* Data format: NMEA-0183 (GSV, GGA, RMC, GSA, and VTG sentences);
* GNSS current consumption: 100 mA;
* GNSS antenna: active or passive. Figure 2: The SIM7600E-H (**left**) and the EMB-LR1276S (**right**). For network monitoring, the SIM7600E-H provides a \"netlight\" pin that can control a network status LED (D1 in Figure 2). If the LED is always on, it means that the module is searching for the network. If the LED is blinking with a 200 ms on/off period, the module is registered to a 4G network. In that case, if the blinking period is longer, the module is registered to a 2G or 3G network. On the board, the usage of the status LED is optional (J2 jumper in Figure 2), and it is not used when the sensing device is outsourced. The second communication module is the EMB-LR12765 from the Embit company. The core of this wireless module is a SAMR34 ultra-low-power microcontroller that includes a 32-bit ARM Cortex-M0+ processor with 48 MHz clock frequency, 256 KB of Flash memory, and 40 KB of SRAM memory. It is equipped with a UHF (Ultra-High-Frequency) transceiver that supports the LoRaWAN (Long-Range Wide Area Network) long-range wireless protocol. The LoRaWAN is a telecommunication protocol for low-speed communication by radio. It provides low-power communication and Internet access according to LoRa technology (2009) via gateways. This protocol is mainly used for smart city, industrial, and agricultural applications. Similarly, as in other widely used wireless protocols, the LoRaWAN operates in the ISM (Industrial, Scientific, and Medical) unlicensed spectrum bands, where its physical layer establishes the communication channel between nodes and gateways.