Design And Implementation Of Data Acquisition System Based On CoAP

In recent years,Hulun Lake watershed is facing serious challenges and itsecological environment is very fragile.To satisfy the demand of Hulun Lake wate-rshed environmental big data collection,a data acquisition system was designedbased on the Constrained Application Protocol(CoAP).It has the characteristics ofbetter compatibility and high transmission efficiency.The basic principle and implementation method of CoAP was discussed indetail.The request/response model,packet format,message transfer mechanism areanalyzed.The implementation method of CoAP protocol was put forward based on theRT-Thread operating system,including the aspects of packet format,the interfacefunction, and the implementation process. This project designed a complete acquisitionsystem, which contains sensor nodes, CoAP gateway nodes and a data center.The sensornode and the CoAP gateway node are studied in this paper. Sensor nodes focus oncollecting environmental data and sending data to CoAP gateway nodes, the CoAPgateway nodes concentrate on tabulating data and uploading it to the data center in thetype of CoAP packets.The design realizes the remote data acquision and networksharing of Hulun Lake watershed environmental data.The study completed the hardwareand software design of sensor nodes and gateway nodes.Sensor nodes chooseSTM32F103as the core controller,and it also extended the temperature，the humidityand the light sensor interface circuit,etc. The STM32F407chip was selected as the corecontroller of the CoAP gateway node.It also realized the access to Internet through theEthernet interface circuit which is based on RMII standard interface.The ZigBeewireless network was used to complete the data communication between the sensornodes and the CoAP gateway nodes.The software design of sensor node and CoAPgateway node was completed based on the RT-Thread operating system.The mainsoftware modules,including the sensor data acquisition module,the ZigBee datacommunication module and the CoAP client protocol module,are dicussed in detail.The thread relationship sequence diagram and the software flow chart were also put forwardin the paper. JSON data format is applied in the payload of the CoAP packet,enhancingthe analyticity of CoAP message.The design implements a demo system including one sensor node and one CoAPgateway node.The test of the data acquisition,data gathering,CoAP message uploadingwas done，and the experimental results show that the system is in a good running effectand it has the characteristics of small quantities of data network data.