Are you sending AT+IPR command to change the baud rate after switching to data mode? This is because, once the V24 link switches to data mode, you cannot change the baud rate settings.
So, to solve the problem, you can do the following:
- Send the AT+IPR command from the embedded application.
- Wait for OK.
- When OK is received, subscribe to a timer. This is to provide some time to the module to actually change the V24 serial speed.
- When the timer expires (and you get a call to timer callback function), subscribe to FCM and then switch to data mode.
- Change the baud rate of your external application (like hyperterminal) to the one that you have set using AT+IPR command.
The module should work fine after these steps.
In case, you are sending AT+IPR command from external application (like hyperterminal), then you should first send the command and then try to subscribe to FCM flow and probably switch it to data mode.
Hope this helps you solve your problem.
Open AT Fan.