| With the advancement and widespread application of Ethernet technology,network clock synchronization technology has been deeply applied to many fields.However,general-purpose Ethernet still has the problems of long delay time and low synchronization accuracy,and it cannot be used in occasions such as control and measurement thatrequire higher accuracy.At present,the IEEE1588 precise time synchronization protocol can achieve higher synchronization accuracy based on the application of Ethernet technology,and meet the requirements of related applications,and is subject to more and more research and applications.This dissertation first introduces several commonly used clock synchronization technologies,describes the implementation methods and synchronization accuracy of related technologies,compares their advantages and disadvantages,and proposes that the IEEE1588 synchronization protocol has higher accuracy and a wide range of application scenarios.After that,the implementation principle of the IEEE1588 synchronization protocol is mainly described,and the network topology of the system and the update process of the state of each clock in the network are given.Secondly,based on the IEEE1588 protocol,the system-related software and hardware solutions are designed.In terms of hardware,the STM32F407 processor with the core contains and supports the IEEE1588 protocol is used to implement related protocol stacks and IEEE1588 application layer functions,and the DP83640 PHY chip integrated and supports the IEEE1588 protocol is used to achieve marking timestamps close to the physical layer,thereby further improving Synchronization accuracy,design related hardware peripheral circuits to realize hardware related functions.In terms of software,considering communication needs and limited hardware resources,the Lwip protocol stack was transplanted instead of the TCP/IP protocol stack to complete the transmission of IEEE1588v2 messages.At the same time,it provides a message interface for the application layer and the MAC layer.The STM32F407 processor transplants the IEEE1588 protocol for Run the best master clock algorithm,IEEE1588 message state machine and message data processing functions,control the DP83640 chip to mark the time stamp,so as to achieve reliable software and hardware communication.Finally,the function and test platform of the system are designed and built,and the external satellite clock is configured to output 1PPS standard second pulse signal to provide clock source for the main clock.Two different connection modes between the master and slave clocks are designed,which are direct connection of network cable and switch connection.The influence of access to external network nodes on synchronization accuracy is studied,and the message sending interval is adjusted,The influence of different message intervals on synchronization results is studied.The clock synchronization system designed in this dissertation is better than100 ns when the network cable is directly connected and the message sending interval is one second.The test results show that the system can achieve high-precision clock synchronization. |
