Extending the application

The AT commands in the Serial LTE modem are implemented with the Custom AT commands library. You can extend the Serial LTE modem application by adding your own AT commands.

Adding AT commands

If you want to implement a custom AT command in SLM, you will need to follow the instructions in the Custom AT commands library documentation. Setting the AT command filter and callback with the AT_CMD_CUSTOM macro is enough for a custom AT command that does not require setup or teardown.

As a preferred alternative to the AT_CMD_CUSTOM macro, SLM defines the SLM_AT_CMD_CUSTOM macro, which is a wrapper around the AT_CMD_CUSTOM macro. The SLM_AT_CMD_CUSTOM macro pre-processes the AT command parameters for the AT command callback and sets the default OK response if the callback returns successfully.

If your custom AT command requires setup or teardown, you will need to perform the following steps:

1. Create a header file in applications/serial_lte_modem/src/. The file must expose the following function declarations:

   • *_init() - Your setup function for the custom AT command.

   • *_uninit() - Your teardown function for the custom AT command.

2. Create a corresponding .c file in applications/serial_lte_modem/src/. The file must implement the following functions:

   • Your AT command callback, which is declared with the AT_CMD_CUSTOM macro.

   • *_init() - Your setup function for the custom AT command.

   • *_uninit() - Your teardown function for the custom AT command. Make sure that the teardown function exits successfully. It will be called before entering power saving states or shutting down.

3. Edit applications/serial_lte_modem/src/slm_at_commands.c and make the following changes:

   1. Include your header file.

   2. In the slm_at_init() function, add a call to your setup function.

   3. In the slm_at_uninit() function, add a call to your teardown function.