Automatic switching circuit for RS232 interface and RS485 interface and serial port liquid crystal display module

The invention is applied to the field of serial port communication, and provides an automatic switching circuit for an RS232 interface and an RS485 interface and a serial port liquid crystal display module. The automatic switching circuit comprises a first photoelectric isolation circuit, a second photoelectric isolation circuit, a serial port state detection circuit, a power control circuit, a data transmission and reception control circuit, an RS485 transceiver and a common channel isolation circuit. In the embodiment of the invention, when the automatic switching circuit adopts a common data display channel for the RS232 interface and the RS485 interface to communicate with a master control micro control unit (MCU), and the common channel is completely isolated, so that the problem of mutual interference of the common channel is solved; the serial port state detection circuit judges the current working conditions of the RS232 interface and the RS485 interface, and is matched with the power control circuit to timely cut off power supplied to the RS485 interface, so that the problem of possible interference when the RS232 interface and the RS485 interface are simultaneously connected can be solved; and in addition, a photoelectric isolation method is adopted to prevent surge and lightning, so that the automatic switching circuit can be well applied to industrial application places.