My experience with these units...

1. BAUD rate varies so try them all.
2. Some expect chars in caps and some don't care
3. Some expect a question mark after the command and some don't e.g AT?
4. Some require CR and some don't.
5. Some only stay in AT mode for a second on boot and thus I found I had to set it up in steps, e.g write program to set PIN, then another to set NAME and so on..

Reason for this is too many clones that do not have full software and commands installed

My experience with these units...

1. BAUD rate varies so try them all.
2. Some expect chars in caps and some don't care
3. Some expect a question mark after the command and some don't e.g AT?
4. Some require CR and some don't.
5. Some only stay in AT mode for a second on boot and thus I found I had to set it up in steps, e.g write program to set PIN, then another to set NAME and so on..

Reason for this is that many clones do not have full software and commands installed.