Disable AT commands before user application


#1

Hi.
I have a product based on SL6087 SW modem. I’d like to disable AT command execution from the power up moment. There is a piece of code which changes FCM flow in the application using “adl_fcmSwitchV24State” function and it works great, but there is a slight moment before application start, when AT commands are handled, so it is possible to send “AT+WOPEN=0” command to disable application and “hack” the device. Desired communication scheme is described as follows:
UART1 - own protocol, AT commands after authentication (software switch using FCM)
UART2 - not supported by hardware
USB - not supported by hardware.

Is it possible disable UART1 and enable it within application AFTER fcm switch?
I would appreciate any help.


#2

Remember that even if you switch your modem to data mode with adl_fcmSwitchV24State function, external applications can still switch it back to AT mode with “+++” sequence. So you should control your uart handler to keep being in data mode always.
But i think you can not prevent any external application attemps breaking the data mode with “+++”. This will bother your open at application. You can also think about phisical protection for uart port insead.


#3

Thanks zafer for the heads up about ‘+++’ sequence.

Is it possible to subscribe to FCM after opening with adl_OpenDevice port closed with +WMFM? What I want to achieve is:

  1. Close UART1 from UART2/3 with AT+WMFM=0,0,1 during production,
  2. Disable WDWL and WOPEN with adl security functions,
  3. Open UART1 in application with adl_OpenDevice,
  4. Subscribe to FCM to be able to switch between data and AT commands on demand after authentication.

Thanks for any clues.
Regards