Short-circuit the CONFIG pin to the ground wire (GND pin), and then turn on the power supply. At this time, the module enters the configuration state. In this state, the configuration of the module is as follows:

The address code is 00H

Baud rate 9600 bps

Prohibit checksum

ASCII character communication protocol

At this time, you can modify the ISO 4021A module's baud rate, checksum status and other parameters through the configuration command, or select the communication protocol by setting the module's communication protocol command.

When you are not sure about the specific configuration of a certain module, you can also install the configuration jumper to make the module enter the configuration state, and then reconfigure the module.