The main function of RS-485 communication circuit is to realize the automatic address distribution and fault location of the equipment along the system. The RS485 transceiver chip is max3088, a low-power data transceiver chip produced by Maxim company. When the enable terminal (2-pin) of max3088 chip receiver is low power level, the chip is in the transmitting state; when the enable terminal (3-pin) of the transmitter is high power level, the chip is in the receiving state. The enable end and the receiving end of the chip are connected with the PA8, RXD and TXD end of STM32 through optocoupler isolation voltage regulation and Schmitt trigger shaping.