Shenzhen Siwei Wireless Technology Co., Ltd. independently developed a wireless network multi-point acquisition system. The system adopts wireless networking mode for temperature, voltage acquisition and real-time monitoring. The system is divided into acquisition terminal and centralized terminal. section. The modules used in the two parts are si4463 wireless modules independently developed by Siwei. Each network consists of one centralized terminal and 64 measuring terminals (can be extended to 3000 measuring terminals). The same environment can allow 40 networks to exist simultaneously.
The working mode of the system is uploaded to the centralized end through the collecting temperature of the collecting end, and then uploaded to the server by the centralized end. There are 64 acquisition ends in a network. When 64 acquisition ends upload the collected temperature, there will be a problem. The transmission time of each node is random, and it may collide with other node data. It is also possible. No collision will occur. In this way, our packet loss rate cannot be guaranteed (package loss: the collected temperature data is lost during the communication transmission). Based on this problem, our engineers developed a function: automatic time synchronization.
A brief description is as follows:
The centralized end and the temperature measuring end of all networks need a unified time, and the uploading time is determined according to the ID, so that different points can be prevented from being uploaded at the same time point.
How time synchronization is implemented:
The upload time of each node in the same network is planned. When each node launches at the time point we set, there will be no two points to launch together, and no data collision will occur . For example, the No. 1 machine is sent in 1 second, and the No. 2 machine is sent in 2 seconds, so that they can be shifted from each other. In order to ensure that the time is the same, you have to ensure that each machine's 1 second is the same time, so you have to synchronize the time, so that 1 second in the whole system is the same time point, 2 seconds is also the same time point.
Points to note:
Because the crystal oscillator is biased, after running for a long time, everyone's time will slowly shift from the original time, which may be fast or slow. Therefore, in order to ensure that the time deviation is within the allowable range, it is necessary to control the deviation of the crystal oscillator, and the timing should be time synchronized.