A set of RS485 communication circuits that do not need to be controlled

: R65 is disconnected. r66 is connected to the 3.3v voltage. rx422t is the sending end. It is used with 485tx and rx422r and 485rx. The circuit itself is not difficult. Maybe you have found out what I want to say.

The De and Ro terminals are connected at any time, but they are disconnected from rs485_en. How can we control the direction of sending and receiving?

This circuit is not logical, but it is feasible after the author's verification! The De and Ro segments are low by default, and the module is in the accept state. As long as the level of the Tx end is the same as that of the De, the RE can be sent.

In this way, some common serial ports can be extended into a 485 circuit without knowing the specific principle, but this can indeed send and receive normally. If you want to explain this circuit!