Since the establishment of the Internet of Things concept in 1998, its development has gradually evolved from sensor networks, to data acquisition, target control, and the wireless communication technology used has also evolved from the initial form of RFID + Internet to various forms of terminal network + Internet. .
At present, the most important core of IoT application equipment is the MQTT server. Using the MQTT protocol for data communication can avoid the complicated problem of server construction in the conventional C/S architecture. The MQTT server is built on the public network in advance, and all terminal devices are used as customers. The terminal accesses the server, using the MQTT publish/subscribe mode, and through the forwarding of the MQTT server, the communication between devices can be realized. At the same time, due to the publish and subscribe mechanism, multiple clients can subscribe and publish the same topic at the same time, which can realize the intercommunication of devices. Data unicast and multicast. At present, the three major Internet leading companies in the Internet all have related IoT services, as well as platforms such as One Net, and the server side is mature.
MQTT communication transport protocol
Regarding data communication protocols, the protocols currently used by everyone are different, some are private protocols, some are based on JSON, some are commonly used by industrial equipment, etc. Among them, the JSON protocol is widely used in network communication, based on the JSON protocol key-value pair , in the form of data points, which can transmit data information well.
Terminals and gateways, the terminal part can be various, on the industrial Internet, the terminal can be a PLC or an IO device based on MODBUS control, such devices are transferred to the RS485 bus and RS232 bus through the network to realize the terminal and the platform, the terminal and the terminal. Terminal communication; on the agricultural Internet, network to LORA wireless technology communication can be used, and the data protocol can be JSON to MODBUS or other, to realize wireless communication between terminal equipment and platform, and between equipment and equipment. The above two kinds of management platforms are established on the server side , you can control the equipment, and the sampled data can also be saved on the platform for data analysis.
Digital radio DTU gateway
There are various access methods. Due to the development of wireless communication technology, the network access method of equipment can already choose wired network, optical fiber, WIFI wireless network, 4G network. In addition to communicating with the network, products as gateways also need to transmit data to downstream terminal equipment. These The equipment can be PLC, water meter and electricity meter, ventilation equipment switch, irrigation system switch, air conditioner, TV, washing machine, etc. As long as it can be controlled by electronic means or indirectly through various terminals controlled by other equipment, it can be connected to the network. Meaningful Internet.
A very simple application is the smart home.
For example, in indoor environment adjustment, the gateway detects sensors through indoor temperature and sound and light sensors, and transmits the collected data to the server. The server controls the air conditioner to adjust the indoor temperature through preset conditions, controls the curtains or electric glass, and controls the light transmittance. A suitable living environment can even be adjusted automatically according to the occupant through deep learning.
For example, intelligent access control, occupants can remotely control, set access control permissions, remotely close doors, indoor monitoring network linkage public security system, prevent robbery, theft and so on.
The technologies used here include edge acquisition, such as acquisition of temperature sensors, noise sensors, and light intensity sensors. These devices can use simple modbus protocol or other protocols. After the gateway collects data, the data is uploaded to the server through the MQTT protocol according to certain conditions. The server can be on the local area network or on the external network. The video surveillance data can be analyzed on the server side, and the records of door opening and access control card swiping can also be synchronized to the cloud.
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