Environmental protection has always been the direction of the country's vigorous rectification. Relevant departments are also continuously promoting the construction of environmental quality monitoring system. The construction and maintenance costs of traditional monitoring methods are high, and it is difficult to popularize in a large area. The HJ212-2017 protocol is a data transmission standard for online pollutant monitoring systems issued by the Science and Technology Standards Department of the Ministry of Ecology and Environment. From the regulatory level, the data transmission standards for the environmental monitoring process are unified. With the continuous development of Internet of Things technology and environmental monitoring business, automatic, intelligent and networked automatic monitoring of environmental quality has become the focus of work for a period of time in the future.Introduction of HJ212-2017 protocol standardThe HJ212-2017 standard communication protocol adopts the response mode, and the complete command is composed of the requester's initiation and the responder's response.NB Module The requester sends a request to the responder, and after the response is received, it sends a request response to the requester, and the handshake is completed. If the requester does not receive a response to the request, it will be processed according to the response timeout.The data structure of the communication protocol is shown in Figure 1. All communication packets are composed of ASCII code characters (except Chinese characters, which use UTf-8 code)Image 15Figure 1 Communication protocol data structureE840-DTU (GPRS-03) is a digital radio product launched by Ebyte that supports transparent transmission of cellular network data. This product has complete software functions and covers most common application scenarios. Users only need to set a simple Realize two-way data transparent transmission from serial port to network server. It is an industrial-grade quad-band GSM\/GPRS data transmission radio.application solutionProgram implementation steps:1. The project operator uses Ebyte E840-DTU (GPRS-03) as the data acquisition instrument, uses the RS485 serial line to connect with the monitoring instrument, and uses the modbus RTU protocol to communicate and collect data;2. E840-DTU (GPRS-03) uploads data to cloud service platform through GPRS cellular network;3. The cloud platform service communicates with the host computer software through the HJ212-2017 protocol standard to realize data monitoring.Figure 2 System topology diagramE840-DTU (GPRS-03) uses the modbus standard protocol as the physical layer communication link, and connects to the transport layer network. It conforms to the HJ212-2017 protocol standard and supports the application layer protocol standard for business interaction. The unified data transmission and interface standards can realize fast dockingGPRS Module detection platform. The system solution can be customized and developed according to the user's project requirements to control the project cost. The wireless transmission solution is directly connected to the base station of telecom operators to quickly upload communication data, saving wiring costs.