What could cause XBee3 LTEM/NB-IoT modem to lose profile

We are using the XBee3 LTEM/NB-IoT modem (u-blox SARA-R410M-02B-01 cellular module), configured for 115200 baud and API operating mode. We run our own 32-bit processor behind the Digi modem, using XBee ANSI C library written by Tom Collins.

We observed that sometimes the modem would lose its configured profile as if a factory reset had occurred, i.e., reversing itself back to 9600 baud and Transparent mode. There is no code in our firmware to issue a factory reset command. I am wondering if there is a hidden, undocumented I/O pin toggling feature that we might have accidentally stumbled upon that would reset a modem to its factory default. Otherwise I can’t find an explanation for this.

No, I am not aware of any pins that can do this on the Cellular component. The only thing I can think of is an ATRE issue to it or holding the reset line low and triggering a reset which would put it in command mode. It would then need to get an ATRE.

The other option is if you have not written the settings to memory using the WR command and then a power cycle occurred.

mvut - Thanks for the response. I am conducting some tests trying to reproduce this issue.

The hypothesis is that quick back-to-back resets on the Digi XBee modem (pin #5) causes some kind of corruption either in the u-blox SARA-R410M-02B module or the Digi EFM32 processor, and the corruption triggers a factory reset.

Digi does recommend a clean shutdown when powering off the radio or resetting. Details can be found here: https://www.digi.com/resources/documentation/Digidocs/90002258/#reference/r_clean_shutdown.htm?Highlight=shutdown