Skip to content

u-blox plugin: SIM hot-swap implementation

Alexander Yashin requested to merge alexanderyashin/ModemManager:ublox-sim-hotplug into main

I want to implement a SIM hot-swap feature for u-blox modems(I have SARA-U2 unit), but I have issues and need some help or advise, if possible. I found this feature supported in Telit modems plugin and try to do things similarly.

Description

There are several steps to make SIM hot swap option enabled:

  1. Check SIM hot insertion configuration using +UDCONF=50 command.

    • If this command returns +UDCONF=50,1, the hot insertion is already configured, so we do not need to enable it, goto step 4.
    • Otherwise, the hot insertion is not configured, so we need to enable it, goto step 2.

  2. Configure SIM hotplug option using +UDCONF=50,1 command.

    • This command configures the SIM hot insertion feature.
    • The command setting is saved in NVM and will be effective at the next power on (modem reset is required).

  3. Perform modem silent reset using +CFUN=15 command.

    • MT silent reset (with detach from network and saving of NVM parameters), without reset of the SIM card.

  4. Setup CIEV: 12,(X) unsolicited response codes processing. These messages allow us to know if SIM is (un)plugged.

    • Configure the indication of the status of a SIM card(+CIEV URC) using +CMER=1,0,0,1,0 command.

What went wrong

Last commit contains a dirty hack with modem reset on every SIM hot-swap. It works, but I am pretty sure, that it is an overkill and bad solution.

In telit plugin there just a mm_broadband_modem_update_sim_hot_swap_detected call without any resets. I suppose it's not enough in case of u-blox plugin because without modem reset( if I comment line 1010), on any SIM hot-insert/remove this will produce an error:

GLib-GObject-WARNING **: gsignal.c:xxx: instance `yyy' has no handler with id `zzz'

After this warning, MM does not recognize modem correctly: Modem couldn't be initialized: Couldn't check unlock status: SIM not inserted warning is produced. So, this results failed modem state.

MM logs for this (without modem reset): log reduced, log debug

I have no idea, how to debug this.

Comments

There were some comments in the issue:

  1. Is +UDCONF=50 specific to a single u-blox device, or generic for all?

    • This command is available for several products: TOBY-L4 TOBY-L200-02S TOBY-L200-03S TOBY-L201-02S TOBY-L210-02S TOBY-L210-03S TOBY-L210-62S TOBY-L220 TOBY-L280 MPCI-L200-02S MPCI-L200-03S MPCI-L201-02S MPCI-L210-02S MPCI-L210-03S MPCI-L220 MPCI-L280 LARA-R2 TOBY-R2 SARA-U2 LISA-U200-01S LISA-U200-02S LISA-U200-03S LISA-U200-52S LISA-U200-62S LISA-U200-83S LISA-U201 LISA-U230 LISA-U260 LISA-U270 and not generic for all :(
    • For some modules (LARA-R2, TOBY-R2, SARA-U2, LISA-U2) for the correct behavior of the SIM hot insertion feature, the SIM card detection feature must be enabled too.

  2. Is the module re-enumerated after +CFUN=15?

    • Module is not re-enumerate after +CFUN=15 after module connection when SIM hot-swap is not configured (log).
 mmcli -M 
    /org/freedesktop/ModemManager1/Modem/0 [u-blox] SARA-U201
(-) /org/freedesktop/ModemManager1/Modem/0 [u-blox] SARA-U201
(+) /org/freedesktop/ModemManager1/Modem/0 [u-blox] SARA-U201
  • Module is re-enumerated after +CFUN=15 in runtime when SIM hot-swap is detected.
Edited by Alexander Yashin

Merge request reports