Data transmission device adaptive to RS232 and RS485 interfaces

The utility model provides a data transmission device adaptive to RS232 and RS485 interfaces, comprising: an interface decision circuit comprising an absolute value circuit composed of two operational amplifiers and a voltage comparator, the output of the absolute value circuit being used as the input of the voltage comparator; the selection control circuit is composed of a multi-path analog switch chip; a switch common end of the multi-channel analog switch chip is connected with an external wiring terminal, and a switch selection end of the multi-channel analog switch chip is connected with the RS232 interface circuit and the RS485 interface circuit respectively; the control end of the multi-channel analog switch chip is connected with the output of the voltage comparator; and a TXD pin of the microprocessor is directly connected with TTL sending input pins of the RS232 interface circuit and the RS485 interface circuit respectively, and an RXD pin of the microprocessor is connected with TTL receiving output