BG95M3LAR02A03_01.016.01.016 hangs with AT+QMBNCFG="autosel",1

We have used AT+QMBNCFG="autosel",1 with the EG91NAXD successfully to switch profiles when the modem switches between two SIM cards (e.g. AT&T and Soracom).

When I try the same with a BG95M3LAR02A03_01.016.01.016 the modem hangs. Here is the sequence that causes the hang.

Modem pre-configured with AT+QMBNCFG="autosel",1

+CCID: 890117xxxxxxxxxxxxxxxx  <<< AT&T SIM 
<switch SIM to Soracom>
<modem becomes unresponsive to AT commands>

This happens whether I switch from AT&T to Soracom or vice-versa. If I disable autosel with AT+QMBNCFG="autosel",0 I can switch SIM cards with no problems.

Is this a known issue ?


I just tried a BG95M1 - BG95M1LAR02A04_01.002.01.002 and I see the same behavior

Followup - the BG95 (M3 and M1) reboot several seconds after the RDY output if the SIM is detected to have changed.

Since we have GNSS_TXD (pin 27) connected to a UART on our CPU, it is pulled high (UART inactive state) and this may be interrupting the modem reboot, because pin 27 is one of the boot config pins. From the hardware design guide:

“GNSS_TXD (pin 27) and GRFC2 (pin 84) are BOOT_CONFIG pins. Never pull them up before
startup, otherwise the module cannot power on normally.”

IMO GNSS_TXD was a poor choice for a boot/strapping pin since it will always be high when the UART is idle.