DK04 monitoring module and computer communication interface circuit

As shown in the figure, D187 is a universal asynchronous receiver transmitter (UART), and its RX/TX signals are connected to the optocoupler N21, N22 and N29, thus connecting the RS-485 communication interface receiver/transmitter D28 and the microprocessor Device D211 is completely photoelectrically isolated. D197 is a generator, and the currently set communication rate is 9600bit/s. D189 is another universal asynchronous receiver transmitter. Optocouplers N204 and N206 completely isolate the RS-232 local communication port from the microprocessor D211. D209 is a dedicated RS-232 driver chip that converts a single 5V isolated power supply into ±12V communication.