In the IoT era, the layout of the sensor becomes more widespread. All kinds of sensors can be installed as IoT terminal nodes to collect information of the surrounding environment, regardless of office buildings or factories of hundred square meters, town center, or the wilderness. The communication method of the sensor and server varies in different environments. For example, wireless communication methods with low power consumption and longer distances are often adopted in the wilderness due to the long distance between the sensor and the gateway and the battery life that shall be taken into consideration. LoRa, the low-power wide-area wireless technology, is usually applied to this kind of application situation. Though gateways can be installed intensively in office buildings, there are many obstacles and communication interference with different frequency ranges. Therefore, LoRa uses a frequency range lower than 1 GHz to reduce other wireless communications interference.

LoRaWAN is a low-power wide-area network standard issued by LoRa Alliance to regulate the entire system structure and communication protocol. There are specific standards for the terminal node's battery life, the gateway, and server operation. The customized LoRa communication network enables the network architect to completely control the network architecture and use specific protocols to construct a network in a diversified way, such as establishing a client-server star network or tree network.

In the customized LoRa communication network, the terminal node can use the Nuvoton NuMicro® M251 series microcontroller as the main control chip. The M251/M252 series is a low-power 32-bit microcontroller with low power consumption features, wide operating voltage, and quick wakeup from sleep mode, which is especially suitable for IoT applications powered by batteries. Also, the M251/M252 series with rich peripheral not only integrates the VAI to provide secondary communication interface voltage but also can connect to the peripheral sensor module without the level shifter.