SIM hot swapping - what is the expected behavior?

[Nick B]

Hey!

I am unsure if AT!UIMS=n is a Sierra-specific command, but so far I have only seen it in AirPrime devices (I am not well-versed in a wide variety of modems, however, I’m a relative newcomer).  AT!UIMS=? returns the command syntax, which allows the user to select the active U/SIM.  

> AT!UIMS=?
><uim> (SIM interface):
>
>	• 0=UICC1—External UIM interface #1
>
>	• 1=UICC2—External UIM interface #2 or Embedded >UIM interface. Depending on the module, the interface >may be exposed to an external SIM connector or ESIM, or >may be connected internally to an ESIM installed >directly on the module.

Additionally, there is the AT!CUSTOM=“UIM2ENABLE” which takes a 0 or 1, which allows for enabling/disabling the second UIM interface.  By default this is enabled.

The way the SIM hot swapping is handled currently by modemmanager sounds like what may be happening when I restart modemmanager (a new modem and SIM object are created incidentally).  I’ll check if it works with MBIM mode, and  I'll clone the repo to see about adding that API.  It just might be a cool project to sink the old teeth into.


References: 

From the AirPrime EM74xx-MC74xx AT Command Reference
AT!UIMS=n page 116
AT!CUSTOM=“UIM2ENABLE” page 33


Best,

Nicholas