Design Of TDC And WiFi Data Transmission For Multi-beam LiDAR System

Multi-beam LiDAR is currently widely used in autonomous driving,and is almost the most important part of the autonomous driving hardware ecosystem.In this paper,a high-precision,multi-channel Time-to-Digital Converter and a high-speed wireless transmission module has been designed and reached,which aims to satisfy the requirement of the high-speed,high-angle resolution,high-precision multi-beam LiDAR of the research group.Firstly,this paper investigates and summarizes several methods used to realize a TDC in detail.Based on the research on high-precision FPGA-TDC,a design using delay chain interpolation is proposed.The designed TDC includes three basic modules,the basic timing unit,the TDC control unit and the host interface unit.Four sets of 8-channel single-precision TDC and two sets of 4-channel double-precision TDC is implemented on Xilinx XC6SLX9 chip.Each stop channel of the TDC supports measurement of multiple pulses.Secondly,the WiFi transmission system in the embedded environment is investigated.The STM32F767 is selected as the controllor,and the Marvell 88w8686 is used as the WiFi chip,which communicated through the SDIO interface with the controllor.Referring to the register manual and finnware interface manual of the 88w8686 WiFi chip,the WiFi driver is implemented on the STM32F767,the LwIP protocol stack is also transplanted,and the UDP service is built to communicate with the host computer to realize real-time transmission of the LiDAR point cloud data.In order to verify the performance of the implemented TDC and WiFi modules,the paper built a test system and conducted a lot of experiments and tests.The experimental results show that the achieved TDC's resolution is up to 74ps with single precision and 37ps with double precision.The measurement accuracy is equivalent to single precision 41 ps,double precision 31ps,and the system deviation is also analyzed.The average ping value of WiFi module is 1 ms,the highest communication rate in UDP is stable at 24 Mbps.The performance of both TDC and WiFi meets the expected requirements and has good practical value.