Jiangmen Neutrino Experiment Back-end Data Aggregation And Switching Module Design

The jiangmen neutrino experiment is to build a liquid scintillator detector to detect neutrinos and detector's diameter is 35.4 meters.When a neutrino passes through the detector,it is possible to interact with the detector and generate a flickering light signal,which is then converted into an electrical signal through the photomultiplier tube.The signal is digitized in front-end electronics,and the digital result is transmitted to the back-end processing board(BEC)and the commercial switch by long cable.In the experiment,17,000 photomultiplier tubes will be used for photon measurements,and the use of cables between BEC and commercial switches will also reach 17,000.In order to reduce the use of cables between the BEC and commercial switches and to reduce the use of space in the rack,a back-end data aggregation and switching module was designed to replace the commercial access layer switches.With the continuous development of embedded systems,devices related to embedded have become an indispensable part of our lives.Therefore,this thesis uses embedded switches as the backend data aggregation and exchange module.TCP / IP protocol is used to complete embedded switches and Ethernet directly exchanges information.This thesis uses the STM32F767 NI microcontroller as the embedded switch master chip,BCM53286 M as a 100 M Ethernet PHY chip,BCM5482 as a Gigabit Ethernet PHY,combined with the LwIP protocol stack and FreeRTOS real-time operating system,to achieve the function of the embedded switch.FreeRTOS real-time operating system requires low system resources,not only completely free and open source,but also has good real-time,can achieve multi-tasking,can be transplanted and cropped,you can configure the scheduling strategy,RAM footprint is small and so on.The LwIP protocol stack is a lightweight TCP / IP stack,it can reduce the use of memory,and its code streamlining,making it suitable for resource-limited processor platforms.This thesis analyzes in detail the various modules of the embedded switch,including the master control mode,Ethernet module,power module,and the clock and reset signal,completes the design of the entire hardware circuit of the embedded switch and the drawing of the PCB board.Combined with the STM32 controllerCortex-M7 kernel and FreeRTOS operating system features,the FreeRTOS operating system ported to the STM32 controller,to provide task su pport for the application program.Porting LwIP protocol stack to FreeRTOS op erating system and writing drivers for the underlying network interface layer Programs that implement TCP communication.Iperf adopts the bandwidth test on the embedded interactive machine.The server side batches the commands and measures the bandwidth of multiple ports.The total bandwidth does not exceed the maximum transmission rate of TCP.After inserting the embedded switch into the BEC,and testing the bandwidth,the test results show that this method can effectively reduce the cable usage,reduce the rack space,and improve system reliability.