EM9190 - Insert Sim


I’m having an issue identifying SIM cards on new motherboard design.
the problem exists both by trying EM9190 and EM7421.
The design includes two SIM sockets and I tried inserting the sim to both of them without success.
right now I have EM9190 inserted on motherboard and I installed SierraWireless_SDX55_Drivers.exe that was found under EM9190 windows drivers.
On device manager, I can find Sierra Wireless HS-USB Modem 90D6 #2 under Modems.

here is the design of the motherboard, and here is the design of Key-b M.2 Module.
Could you identify anything in the design that could be causing this problem?

from my check on hardware, SIM1_PWR (UIM-PWR - Pin 36) and SIM2_PWR (GPIO (1.8V) -Pin 48) are 0V!
maybe this be the cause of the problem, and I have no idea why this voltage is zero.

Best Regards,
Firas Abdel Ghani

Hi @firas.abdelghani
According to your description, the module is showing under Modems in Device Manager, please open the port and give me the result of below commands:


If both commands above do not respond or respond “Error”
For this case, there are 2 scenarios that cause the issue:

  1. Hardware issue, please try EM9190 module on Sierra board. If it still works well on the Sierra board then the issue may be caused by your board.
    If both Sierra board and your board have issue
  2. Firmware issue, what firmware version is your running?



can you please give more details about “the port” and how it’s used in Windows 10 and Linux?


we were successfully able to communicate with the device and got the following output:
FW: SWI9X50C_01.14.03.00
here we tried EM7421 module.
what could be the problem for not being to identify the sim card?
we checked the SIM_DETECT (PIN 66) and before inserting the card the voltage was 0V, and after inserting, the voltage was 1.6V.
is 1.6V the correct voltage for open circuit? does EM7421 has internal pull up to 1.6V?

Best Regards,


we fixed a HW issue with the SIM and now EM9191 works but EM7421 doesn’t work.
we will open a different case for EM7421.

Thank you,