MQTT and Modbus can complement each other to improve the performance of the Internet of Things. Using Modbus as a local interface to manage devices, and using MQTT as a global protocol to expand the range of devices, both have played an important role.

When the communication distance is tens of meters to thousands of meters, the RS-485 serial bus standard is widely used. RS-485 uses balanced transmission and differential reception, so it has the ability to suppress common mode interference. The standard value of the maximum transmission distance of the RS-485 interface is 4000 feet (about 1219 meters), which is actually up to 3000 meters. In add···

Serial port and COM port refer to the physical interface form (hardware). And TTL, RS-232, RS-485 refer to the level standard (electrical signal).

Modbus gateway can be called Ethernet communication gateway, it can realize the conversion between Modbus RTU/ASCII and Modbus TCP protocol. The Modbus protocol is divided into two types, one is Modbus RTU (or ASCII) based on RS485, and the other is Modbus TCP based on Ethernet. Modbus gateway is a converter that converts Modubs RTU device data into Modbus TCP data.

Design features of NB-IoT network:Ultra-low power consumption: With the addition of the PSM function, the current consumption of the terminal in this mode is about 3uA, even if the dry battery is used, the module can be driven for 10 years;

NB-IoT protocol is a set of wireless cellular network communication rules designed to make full use of precious wireless spectrum resources and time resources to meet the needs of LPWA. Its role is to formulate a set of syntax, semantics and timing for information interaction. In short It is the rules that stipulate what language the communication participants use, what they mean, and who speaks w···

LoRa spread spectrum principle: By using a high spreading factor, LoRa technology can transmit small-capacity data through a wide range of radio frequency spectrum. In fact, when you measure with a spectrum analyzer, the data looks like noise, but the difference is that the noise is uncorrelated, and the data is correlated. Based on this, the data can actually be extracted from the noise.

LoRa integrates digital spread spectrum, digital signal processing and forward error correction coding technology, with unprecedented performance. Previously, only those high-level industrial radio communications would integrate these technologies, and with the introduction of LoRa, the situation in the field of embedded wireless communications has undergone a complete change.

LoRa mainly operates in free frequency bands worldwide (ie unlicensed frequency bands), including 433, 868, 915 MHz, etc. LoRa network is mainly composed of four parts: terminal (built-in LoRa module), gateway (or base station), server and cloud. LoRa application data can be transmitted in both directions.

GPRS DTU adopts high-performance industrial-grade 32-bit communication processor, industrial-grade wireless module and industrial-grade GPS module. It uses embedded real-time operating system as the software support platform. It also provides RS232 and RS485 (or RS422) interfaces, which can be directly connected to the serial port. Equipment to realize data transparent transmission function