EM9191 USB interface not detected on Windows PC


I am trying to connect EM9191 module via USB interface on Windows machine.

  1. I have installed latest device driver on my Windows 10 host PC.
  2. PCIe_Dis signal is pulled high
  3. there is no activity observed on Device Manager when USB cable plugged or unplugged.

We are using only USB2.0 interface, please suggest the pointer.
Do we need to use any USB custom cable, If yes please suggest the USB custom cable drawing.

Our electrical implementation is as per below :


Hi @himgupta,
Could you please share with me some information as below:

  1. Please try with USB 3.1 to see if the issue still happens?
  2. Are you using Sierra board or custom board? If you are using custom board, Please try using the Sierra board. Do the issue still happens in this case?
  3. If you are using a Sierra board and the issue still happens, please try with another PC to see if the issue still happens?
  4. What firmware version is your EM9191 running?



After providing supply voltage 3.3V to VBUS pin (Pin 22) , Wireless module detected on PC


I am trying to communicate via Com6 on teraterm serial console but not getting at AT command response.

  1. Please confirm baud rate to be used.
  2. Is there any specific setting to be used with teraterm serial terminal?
  3. Is there any command to enable Serial access.


Hi @himgupta

Please double click “Sierra Wireless WWAN Modem” and check the COM port in the Modem tab, then use this COM port on Tera Term serial console to communicate AT command with the module.