Design Of Multi-channel Analog And Digital Hybrid Acquisition And Transmission Equipment Based On FPGA

In astronautics engineering test,it is necessary to collect and frame physical parameters and image data of aircraft,such as temperature and pressure,and transmit data packets to the ground control platform for further processing and analysis after the test.For this application,based on the project of "the development of a telemetry system acquisition and compilation controller",The device based on FPGA with the function of analog and digital acquisition,encoding and data transmission is designed.In application,the equipment can collect multi-channel analog data,receive digital data,and realize the mixed programming.Finally,through the long-distance transmission link,the data transmission interaction between the equipment and the ground control platform is realized.Firstly,according to the technical conditions and performance requirements of the subject,the overall design of the framework is carried out.Secondly,the construction of analog data acquisition circuit and digital data transceiver circuit is described.By adding drivers,equalizers and terminal resistors to solve the problem of signal attenuation in long-distance transmission.The selection of transmission line,signal reflection and attenuation characteristics of transmission line are also analyzed.Then,starting with the design of embedded software,the internal control logic of FPGA is designed,and four key points,such as switching control of acquisition channel,dual-stream ADC acquisition timing sequence,analog and digital mixed framing technology,and optimization of packet counting handshake protocol in feedback retransmission and error correction mechanism,are described in detail.Finally,the upper computer,the ground control platform,the optical transceiver,the memory and the equipment were used to build a closed-loop test system.In turn,the data acquisition accuracy,LVDS long-distance transmission error rate and the overall function were tested successively.Through equipment analysis and a large number of tests,it is proved that the analog-digital mixed acquisition and transmission equipment can complete 64 channels of analog data acquisition,the acquisition accuracy is better than 1‰,and can realize 2channels of PCM data and 2 channels of LVDS image data reception.Under the condition that the transmission distance is 120 m and the transmission medium is twisted-pair shielded cable,the high reliable data communication of 180Mbit/s can be realized.