| Based on STM32F407 chip,the communication function between the surface telemetry board and the underground telemetry board is realized.The single core cable is used as the transmission medium to upload the underground data and send the upper computer instructions.The coding program is used to complete the coding of effective data according to the coding rules of differential man code.The encoded man code data is transmitted by SPI + DMA and loaded on the cable through the driving circuit,which is composed of AD847 operation amplifier circuit and TD823 power amplifier circuit.The receiving end sends the man code signal received from the cable to the two-stage amplification circuit and the comparison circuit,and then outputs the man code high and low levels.The MCU receives the man code level signal output by the way of EXTI + TIM3,and decodes the differential man code data through the decoding program.The design of network interface based on w5500 Ethernet chip realizes the communication between upper computer and ground telemetry board.After the completion of the overall design of the system,through consulting the relevant parameters of the single core cable,the communication test experiment of 5000 m analog single core cable was carried out.In the experiment,it was found that the original self-defined synchronization head had lost the edge.After resetting the synchronization head,the problem of the loss of the edge of the signal waveform of the receiving terminal was successfully solved.The waveforms of man code signal in each stage of transmission are detected by oscilloscope,and the feasibility of hardware circuit and codec program is verified.When the transmission speed of the system is 40.6kbit/s,the reliability of data transmission is high,and the stability of the transmission signal waveform can successfully complete the decoding of man code data. |
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