[User Manual] How-to-send-AT-command:
1.The product of the USR have AT command mode. If you forget your setting or make a wrong setting, you can enter AT command mode, inquire or change the setting.
2.The diagram of enter AT command is as follow.
3.We use the USR-TCP232-TEST software to send serial command. You can use your own serial software or MCU send command to our module.
4.Configure the serial parameters. Open the serial port.
5.Send +++ to serial. If you add a SPACE or ENTER, that will not return the correct character.
6.If you give a correct command, the module will return an 'a'
7.When you receive an 'a', you should send an 'a' at once(in 3 seconds). You can not add any SPACE or ENTER either.
8.The module will return +Ok if the module enter the AT command mode.
9.Now you can send AT command to the module, but you should add an ENTER after your command.